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Data in the literature on the use of ceftazidime-avibactam (CAZ-AVI) in carbapenem-resistant Klebsiella pneumoniae bloodstream infections (CRKP-BSIs) are limited especially in OXA-48 (Oxacillinase-48) predominant regions. Our study aimed to evaluate the effect of CAZ-AVI use on outcomes in CRKP-BSIs in Turkey, where OXA-48 is endemic. A multicenter retrospective observational study was conducted between January 2017 and September 2021. The effects of clinical and treatment characteristics on 30-day mortality and relapse in CRKP-BSIs were analyzed. Predictors of outcomes were detected using a Cox regression model. The study enrolled 106 adults with CAZ-AVI-sensitive CRKP-BSIs who received CAZ-AVI for at least 72 h. Patients who received CAZ-AVI as initial therapy had lower mortality rates when compared to those who switched from last resort regimens [14.3% (n = 3/21) vs. 37.7% (n = 32/85), p = 0.04]. In multivariate analysis, older age and severe neutropenia were detected to be associated with higher mortality, significantly. Initiation of CAZ-AVI on the day of blood culture was obtained, was found to be significantly associated with lower mortality (HR: 0.25, CI: 0.07–0.84, p = 0.025). CAZ-AVI monotherapy is an important treatment option for CRKP-BSIs in OXA-48 endemic areas. Early initiation of CAZ-AVI should be preferred rather than switching from a last-resort regimen as it profoundly improves the survival rates. [ABSTRACT FROM AUTHOR]

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections poses global challenges, with limited options available for targeted therapy. Polymyxin was been regarded as one of the most important last-resort antimicrobial agents. Many factors could accelerate the resistance evolution of polymyxin. Insertion sequence (IS) inserted into mgrB is the main polymyxin resistance mechanism in K. pneumoniae. In this study, two CRKPs (KP31157 and KP31311) were isolated from the urine of a patient, shifting from susceptible to resistant as the mgrB inserted by ISkpn14. We intended to explore the origin of the IS and underlying mechanisms resulting in polymyxin resistance. Methods: The within-host evolution relationship and molecular features of both CRKPs were determined by pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS). pKP31311_KPC-2 plasmid genome structures contained in the above two CRKPs were aligned with the homologic plasmids, retrieved from the NCBI genome database via comparative genomic analysis. The plasmids encoding ISkpn14 elements flanked by direct repeat (DR) or not were analyzed. The mRNA expression, plasmid curing and in vitro antibiotics inducing experiment were employed to understand the potential mechanism of polymyxin resistance. Results: Both strains, sharing homology, exhibited polymyxin resistance due to the insertion of ISkpn14 into the mgrB gene, influenced by minocycline exposure. Minocycline and tigecycline could accelerate polymyxin resistance (P < 0.05), validated by an in vitro induction experiment. The ISkpn14 without DR flanked expressed about 4 times higher than that with DR. The frequency of the mgrB insertion induced by polymyxin was significantly reduced (0 strain detected) after the blaKPC−2-carrying plasmid was eliminated. Conclusions: This study provides direct experimental evidence that the ISkpn14 element causing mgrB inactivation and polymyxin resistance in K. pneumoniae originates from blaKPC−2-carrying plasmids. Minocycline exposure will accelerate the evolution of polymyxin resistance. Understanding the dynamics of IS transposition and its association with antibiotic exposure is crucial for developing effective strategies to reduce the emergence of polymyxin resistance in CRKP. Highlights: Directly proved ISkpn14 element inserted into the chromosomal mgrB gene in polymyxin-resistant K. pneumoniae originated from blaKPC-2-carrying plasmid. Exposure to minocycline could accelerate in vivo and in vitro polymyxin resistance evolution. ISkpn14 without DR flanked could express transposase more than that with DR flanked. [ABSTRACT FROM AUTHOR]

Background: The human gut microbiota is an extensive population of microorganisms, and it shows significant variations between periods of optimal health and periods of illness. Vancomycin-resistant Enterococcus (VRE) and carbapenem-resistant Klebsiella pneumoniae (CRKP) are both pathogenic agents (BPAs) that can colonize in the gut after dysbiosis of microbiotal composition following antibiotic treatment. Methods: This study aimed to investigate the impact of antibiotics on the microbiotal composition of the gut. For this purpose, the first pass meconiums of 20 patients and the first rectal swabs containing BPAs of the same patients after antibiotic treatment were studied using next-generation sequencing-based 16S rRNA gene analysis. The V1–V9 region of 16S rRNA was sequenced with Oxford Nanopore. Results: Twenty-five phyla were detected in the meconiums, and 12 of them were absent after antibiotic treatment. The four most prevalent phyla in meconiums were Bacillota, Pseudomonadota, Bacteroidota, and Actinomycetota. Only the relative abundance of Pseudomonadota was increased, while a significant decrease was observed in the other three phyla (p < 0.05). A significant decrease was observed in alpha-diversity in rectal swabs containing BPAs versus meconiums (p = 0.00408), whereas an increased variance was observed in beta-diversity in all samples (p < 0.05). As a result of a LEfSe analysis, Pseudomonadota was found to have a higher relative abundance in rectal swabs, and Bacillota was significantly higher in the meconiums of the twins. Conclusions: Our study strongly verified the relationship between the administration of antibiotics, dysbiosis, and colonization of BPAs in the infants' gut microbiota. Further research would be beneficial and needed, comprising the natural development process of the infants' gut microbiota. [ABSTRACT FROM AUTHOR]

Carbapenem-resistant Klebsiella pneumoniae (CR-Kp) is currently a serious global concern. Antimicrobial stewardship programs (ASPs) are one of the key strategies to overcome this resistance. However, evidence about the long-term clinical and ecological impacts of ASPs is scarce. A multidisciplinary team conducted a multifaceted intervention in a CR-Kp endemic hospital over a 6-year period. We assessed the monthly long-term impacts of ASPs on carbapenem use, incidence density (ID), and crude death rates of hospital-acquired CR-Kp infections. Other variables potentially related to CR-Kp incidence and healthcare activity indicators were monitored. Carbapenem use showed a sustained reduction over the long term, with a difference of −66.19% (95% CI −87.03 to −45.34) between the expected pre-intervention trend consumption value and that obtained six years after starting the program. The ID of CR-Kp also decreased significantly and was maintained over the long term, with a relative reduction of −88.14% (95% CI; −100.4 to −75.85) at the end of the study period. The crude death rate of CR-Kp at 14 and 28 days decreased significantly after the intervention and remained steady after six years. Infection control indicator trends remained stable. This mixed ASP contributed to reducing the high incidence of infections and mortality rates of CR-Kp, achieving a sustained ecological and clinical effect. [ABSTRACT FROM AUTHOR]

Abstract Data in the literature on the use of ceftazidime-avibactam (CAZ-AVI) in carbapenem-resistant Klebsiella pneumoniae bloodstream infections (CRKP-BSIs) are limited especially in OXA-48 (Oxacillinase-48) predominant regions. Our study aimed to evaluate the effect of CAZ-AVI use on outcomes in CRKP-BSIs in Turkey, where OXA-48 is endemic. A multicenter retrospective observational study was conducted between January 2017 and September 2021. The effects of clinical and treatment characteristics on 30-day mortality and relapse in CRKP-BSIs were analyzed. Predictors of outcomes were detected using a Cox regression model. The study enrolled 106 adults with CAZ-AVI-sensitive CRKP-BSIs who received CAZ-AVI for at least 72 h. Patients who received CAZ-AVI as initial therapy had lower mortality rates when compared to those who switched from last resort regimens [14.3% (n = 3/21) vs. 37.7% (n = 32/85), p = 0.04]. In multivariate analysis, older age and severe neutropenia were detected to be associated with higher mortality, significantly. Initiation of CAZ-AVI on the day of blood culture was obtained, was found to be significantly associated with lower mortality (HR: 0.25, CI: 0.07–0.84, p = 0.025). CAZ-AVI monotherapy is an important treatment option for CRKP-BSIs in OXA-48 endemic areas. Early initiation of CAZ-AVI should be preferred rather than switching from a last-resort regimen as it profoundly improves the survival rates.

Piaopiao Ying,1 Jiajing Chen,2 Yinchai Ye,3 Chang Xu,4 Jianzhong Ye5 1Department of General Medicine, The Affiliated Hospital of Hangzhou Normal University, Hangzhou, People’s Republic of China; 2Department of Nephrology, Taizhou Hospital of Zhejiang Province Affiliated with Wenzhou Medical University, Taizhou, People’s Republic of China; 3Department of General Medicine, The Health Center of Eryuan Town, Wenzhou, People’s Republic of China; 4Department of Intensive Care Medicine, Ningbo No. 2 hospital, Ningbo, People’s Republic of China; 5Department of Clinical Laboratory, Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, People’s Republic of ChinaCorrespondence: Chang Xu, Department of Intensive Care Medicine, Ningbo No. 2 hospital, Ningbo, 41 Xibei Street, Ningbo, 315010, People’s Republic of China, Email xc95121@163.com Jianzhong Ye, Department of Clinical Laboratory, Key Laboratory of Clinical Laboratory Diagnosis and Translational Research of Zhejiang Province, the First Affiliated Hospital of Wenzhou Medical University, Nanbaixiang Street, Ouhai District, Wenzhou, 325000, People’s Republic of China, Email jzye89@163.comObjective: This study aimed to investigate the correlation between computed tomography (CT) derived body composition and 30-day mortality in patients with pulmonary infections caused by carbapenem-resistant Klebsiella pneumoniae (K. pneumoniae).Methods: A total of 89 eligible participants from a tertiary teaching hospital, enrolled between January 1, 2016, and December 31, 2020, were included in the study. We analyzed the relationship between visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), total adipose tissue (TAT), and skeletal muscle (SM) and 30-day mortality in patients infected with carbapenem-resistant K. pneumoniae (CRKP) in the pulmonary region. Furthermore, we established Cox regression models and a personalized nomogram model to predict the probability of 30-day mortality in these infected patients.Results: Individuals with high VAT exhibited a higher likelihood of 30-day all-cause mortality (P< 0.01) and 30-day mortality due to CRKP infection (P< 0.01) compared to those with low VAT. Similar results were observed for TAT. After adjusting for significant comorbidities and other clinical characteristics, Cox regression analysis revealed that male gender (adjusted HR = 4.37; 95% CI = 0.96– 19.92, P=0.06), vasopressor use (adjusted HR = 3.65; 95% CI = 1.04– 12.85, P=0.04), and VAT (adjusted HR = 1.16; 95% CI = 1.01– 1.34, P=0.03) were independent risk factors for 30-day all-cause mortality among these infectious patients.Conclusion: The study results highlight the significant prognostic value of CT-quantified visceral adipose tissue in patients with CRKP pulmonary infection. Individuals with high VAT are more prone to mortality within 30 days compared to those with low VAT.Keywords: body composition, carbapenem-resistant Klebsiella pneumoniae, mortality, visceral adipose tissue, pulmonary infection

Abstract Background Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections poses global challenges, with limited options available for targeted therapy. Polymyxin was been regarded as one of the most important last-resort antimicrobial agents. Many factors could accelerate the resistance evolution of polymyxin. Insertion sequence (IS) inserted into mgrB is the main polymyxin resistance mechanism in K. pneumoniae. In this study, two CRKPs (KP31157 and KP31311) were isolated from the urine of a patient, shifting from susceptible to resistant as the mgrB inserted by ISkpn14. We intended to explore the origin of the IS and underlying mechanisms resulting in polymyxin resistance. Methods The within-host evolution relationship and molecular features of both CRKPs were determined by pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS). pKP31311_KPC-2 plasmid genome structures contained in the above two CRKPs were aligned with the homologic plasmids, retrieved from the NCBI genome database via comparative genomic analysis. The plasmids encoding ISkpn14 elements flanked by direct repeat (DR) or not were analyzed. The mRNA expression, plasmid curing and in vitro antibiotics inducing experiment were employed to understand the potential mechanism of polymyxin resistance. Results Both strains, sharing homology, exhibited polymyxin resistance due to the insertion of ISkpn14 into the mgrB gene, influenced by minocycline exposure. Minocycline and tigecycline could accelerate polymyxin resistance (P

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a global threat, causing serious community- and hospital-acquired infections with limited treatment options. Understanding the local epidemiology of CRKP is crucial for guiding antimicrobial stewardship and infection control measures. This study aimed to investigate the phenotypic characteristics, antimicrobial resistance profiles, and carbapenemase genes among CRKP isolates from the patients in Najaf, Iraq. Methods: This cross-sectional research was performed at diverse hospitals and centers in Najaf, Iraq, from September 2023 to March 2024. The study was approved by the Ethics Committee of Kufa University. CRKP isolates were collected from various health-care facilities and tested for hypermucoviscosity, antimicrobial susceptibility, and carbapenemase production using phenotypic methods. The presence of carbapenemase genes (blaNDM, blaVIM, blaKPC, blaOXA-48, blaOXA-23, and blaOXA-51) was examined by polymerase chain reaction. Results: Of the 27 CRKP isolates, 9 (33.3%) exhibited a hypermucoviscous phenotype. Regarding antimicrobial resistance, 12 (44.4%) were multidrug resistant, 14 (51.9%) were extensively drug resistant, and 1 (3.7%) was pandrug resistant. Phenotypic carbapenemase production was detected in 5 (18.5%) and 11 (40.7%) isolates by the modified Hodge test and E-test metallo-β-lactamase strips, respectively. Molecular analysis revealed that all CRKP harbored the blaOXA-51 gene, whereas blaNDM, blaOXA-23, and blaVIM were detected in 70.4%, 40.7%, and 11.1% of the isolates, respectively. Neither blaKPC nor blaOXA-48 genes were found. In addition, 22 (81.5%) isolates carried multiple carbapenemase genes. Conclusions: The high prevalence of blaOXA-51 and blaNDM carbapenemases, along with the high rates of multidrug resistance among CRKP isolates in Najaf, Iraq, are alarming. This necessitates the immediate implementation of effective antimicrobial stewardship and infection control measures to prevent the further spread of these difficult-to-treat pathogens.

Abstract It remains that intracranial infection has an alarming mortality and morbidity. Klebsiella pneumoniae (KP) have increasingly been isolated in ventriculitis and meningitis episodes. Intracranial infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) account for high mortality. To understand its clinical impact and related risk factors accurately are crucial in the management of bacterial intracranial infection. The retrospective study aimed to delineate the clinical risk of death from intracranial infection and analyze the risk factors. A total of 176 Klebsiella pneumoniae intracranial infectious patients were available to divide into CRKP group and carbapenem-susceptive Klebsiella Pneumoniae (CSKP) group. We performed survival analysis and estimate the time-varying effects of CRKP and CSKP infection on 30-day mortality. Infectious patients caused by CSKP was associated with lower mortality than CRKP group. The risk factors associated with death from intracranial infection caused by Klebsiella pneumoniae included SOFA scores, ventilator therapy, CRKP, and heart failure. Longer hospital stays are independently associated with lower mortality rates. Intracranial infection caused by CRKP was associated with excess mortality. Complex comorbidities mean higher mortality. Active supportive treatment is required for complicated patients with intracranial infections caused by carbapenem-resistant Klebsiella pneumoniae.

ABSTRACT: Objectives: The emergence of carbapenem-resistant Klebsiella pneumoniae presents significant health challenges. Here, we present the structural genome sequence of an NDM-5–producing K. pneumoniae (HZKP2) in China. Methods: Antimicrobial susceptibility tests were conducted via broth microdilution. Whole-genome sequencing was performed for genomic analysis. Wzi and capsular polysaccharide (KL) were analysed using Kaptive. Resistance genes, virulence factors, and comparative genomics analyses were also conducted. Multilocus sequence typing (MLST), replicons type, and core genome MLST analysis were further conducted using BacWGSTdb server. Results: HZKP2 was resistant to cefepime, ceftazidime, ciprofloxacin, ciprofloxacin, meropenem, and ertapenem. It harboured fosA, blaSHV-187, oqxA, oqxB, sul1, dfrA1, tet(A), floR, aph(6)-Id, aph(3′')-Ib, sul2, blaCTX-M-55, and blaNDM-5. Based on the RAST results, 5563 genes that belonged to 398 subsystems were annotated. The complete genome sequence of HZKP2 was characterized as ST1, wzi 19, and KL19, 5 five contigs totalling 5 654 446 bp, including one chromosome and four plasmids. Further analysis found that blaNDM-5 was located in a 46 161 bp IncX3 plasmid (pHZKP2-3). The genetic structure of blaNDM-5 gene was ISKox3-IS26-bleMBL-blaNDM-5-IS5-ISAb125-IS3000. Further analysis revealed that insertion sequences mediated the dissemination of blaNDM-5 from other species of Enterobacterales. Phylogenetic analysis showed that the closest relative was from a human stool specimen in China, which differed by 53 core genome MLST alleles. Conclusions: Our study provides the first structural perspective of the ST1 K. pneumoniae isolate producing NDM-5 in China. These results could provide valuable insights into the genetic characteristics, antimicrobial resistance mechanisms, and transmission dynamics of carbapenem-resistant K. pneumoniae in clinical settings.

Abstract Background Klebsiella pneumoniae (KP) is the second most prevalent Gram-negative bacterium causing bloodstream infections (BSIs). In recent years, the management of BSIs caused by KP has become increasingly complex due to the emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP). Although numerous studies have explored the risk factors for the development of CRKP-BSIs, the mortality of patients with KP-BSIs, and the molecular epidemiological characteristics of CRKP, the variability in data across different populations, countries, and hospitals has led to inconsistent conclusions. In this single-center retrospective observational study, we utilized logistic regression analyses to identify independent risk factors for CRKP-BSIs and factors associated with mortality in KP-BSI patients. Furthermore, a risk factor-based prediction model was developed. CRKP isolates underwent whole-genome sequencing (WGS), followed by an evaluation of microbiological characteristics, including antimicrobial resistance and virulence genes, as well as epidemiological characteristics and phylogenetic analysis. Results Our study included a total of 134 patients with KP-BSIs, comprising 50 individuals infected with CRKP and 84 with carbapenem-susceptible Klebsiella pneumoniae (CSKP). The independent risk factors for CRKP-BSIs were identified as gastric catheterization (OR = 9.143; CI = 1.357–61.618; P = 0.023), prior ICU hospitalization (OR = 4.642; CI = 1.312–16.422; P = 0.017), and detection of CRKP in non-blood sites (OR = 8.112; CI = 2.130-30.894; P = 0.002). Multivariate analysis revealed that microbiologic eradication after 6 days (OR = 3.569; CI = 1.119–11.387; P = 0.032), high Pitt bacteremia score (OR = 1.609; CI = 1.226–2.111; P = 0.001), and inappropriate empirical treatment after BSIs (OR = 6.756; CI = 1.922–23.753; P = 0.003) were independent risk factors for the 28-day mortality in KP-BSIs. The prediction model confirmed that microbiologic eradication after 6.5 days and a Pitt bacteremia score of 4.5 or higher were significant predictors of the 28-day mortality. Bioinformatics analysis identified ST11 as the predominant CRKP sequence type, with bla KPC−2 as the most prevalent gene variant. CRKP stains carried multiple plasmid-mediated resistance genes along with some virulence genes. Phylogenetic analysis indicated the presence of nosocomial transmission of ST11 CRKP within the ICU. Conclusions The analysis of risk factors for developing CRKP-BSIs and the association between KP-BSIs and 28-day mortality, along with the development of a risk factor-based prediction model and the characterization of CRKP strains, enhances clinicians’ understanding of the pathogens responsible for BSIs. This understanding may help in the timely administration of antibiotic therapy for patients with suspected KP-BSIs, potentially improving outcomes.

Abstract Background Klebsiella pneumoniae is the most commonly encountered pathogen in clinical practice. Widespread use of broad-spectrum antibiotics has led to the current global dissemination of carbapenem-resistant K. pneumoniae, which poses a significant threat to antibacterial treatment efficacy and public health. Outer membrane vesicles (OMVs) have been identified as carriers capable of facilitating the transfer of virulence and resistance genes. However, the role of OMVs in carbapenem-resistant K. pneumoniae under external pressures such as antibiotic and phage treatments remains unclear. Methods To isolate and purify OMVs under the pressure of phages and tigecycline, we subjected K. pneumoniae 0692 harboring plasmid-mediated bla NDM-1 and bla KPC-2 genes to density gradient separation. The double-layer plate method was used to isolate MJ1, which efficiently lysed K. pneumoniae 0692 cells. Transmission electron microscopy (TEM) was used to characterize the isolated phages and extract OMV groups for relevant morphological identification. Determination of protein content of each OMV group was conducted through bicinchoninic acid assay (BCA) and proteomic analysis. Results K. pneumoniae 0692 released OMVs in response to different environmental stimuli, which were characterized through TEM as having the typical structure and particle size of OMVs. Phage or tigecycline treatment alone resulted in a slight increase in the mean protein concentration of OMVs secreted by K. pneumoniae 0692 compared to that in the untreated group. However, when phage treatment was combined with tigecycline, there was a significant reduction in the average protein concentration of OMVs compared to tigecycline treatment alone. Proteomics showed that OMVs encapsulated numerous functional proteins and that under different external stresses of phages and tigecycline, the proteins carried by K. pneumoniae 0692-derived OMVs were significantly upregulated or downregulated compared with those in the untreated group. Conclusions This study confirmed the ability of OMVs to carry abundant proteins and highlighted the important role of OMV-associated proteins in bacterial responses to phages and tigecycline, representing an important advancement in microbial resistance research.

Yingjie Zhang,&ast; Guokuo Hou,&ast; Liping Zhang, Shanshan Li Department of Neurosurgery ICU, The Second Hospital & Clinical Medical School, Lanzhou University, Academician Workstation of The Second Hospital & Clinical Medical School, Lanzhou University, Lanzhou, 730000, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Shanshan Li, Tel +8615193185275, Fax +86-931-15193185275, Email 15193185275@163.comBackground: Central Nervous System (CNS) infections caused by Carbapenem-resistant Klebsiella pneumoniae (CRKP) pose a major clinical challenge and are associated with high mortality rates. Polymyxin is used as a salvage treatment for CRKP CNS infection; however, heteroresistance to polymyxin may impact clinical outcomes. In this study, we report a rare case of polymyxin-resistant Klebsiella intracranial infection, which was successfully treated with intravenous and intraventricular antibiotic injections.Case Presentation: A 46-year-old woman with a 1-day history of post-traumatic disturbance of consciousness and cerebrospinal fluid (CSF) rhinorrhea was referred to our hospital. She underwent external ventricular drainage and decompressive craniectomy, and had a persistent fever. A CSF test confirmed intracranial infection. The minimum inhibitory concentration of polymyxin in this patient was 16 μg/mL. She was diagnosed with polymyxin-resistant pan drug-resistant (PDR) Klebsiella pneumoniae (PDR-Kp) intracranial infection. We successfully treated the infection using intravenous ceftazidime/avibactam (CAZ/AVI) and polymyxin B, combined with an intraventricular injection of polymyxin B according to the CSF microbiological culture results.Conclusion: CAZ/AVI combined with polymyxin B may be an effective salvage treatment for CNS infections caused by polymyxin-resistant PDR-KP.Keywords: CNS infection, Carbapenem-resistant Klebsiella pneumoniae, polymyxin-resistant, ceftazidime/avibactam

ABSTRACT: Objectives: This study aimed to isolate a phage capable of lysing carbapenem-resistant Klebsiella pneumoniae (CRKP) and to analyse its biological characteristics and whole-genome sequence. Methods: The phage was isolated and purified from the sewage. Transmission electron microscopy (TEM) was employed to observe the bacteriophage's morphology. Phenotypic characterization of the bacteriophages was determined. The genomic information was analysed. Evolutionary relationships were established through comparative genomics, proteomics, and phylogenetic analysis. Results: The isolation of a virulent phage, named Klebsiella phage vB_KpnM_KpVB3, was notable for forming 6–7 mm transparent circular zones, each surrounded by a distinct halo. The phage had a head diameter of ca. 30 nm and a tail length of ca. 20 nm, being identified as a member of the Myoviridae family and the Caudovirales order. The optimal multiplicity of infection (MOI) was 0.00001, with an incubation period of 20 minutes and a lysis period of 60 minutes, and the number of released phages after lysis was 133±35 PFU/cell. The phage was relatively stable at temperatures ranging from 10°C to 40°C and at pH values ranging from 3 to 11. Its lytic efficiency against CRKP was 30.30%. It has been shown to be able to destroy the biofilm of host bacteria. The bacteriophage genome consists of double-stranded DNA (dsDNA) with a total length of 48,394 base pairs, a GC content of 48.99%, and 78 open reading frames (ORFs). Conclusion: The study resulted in the isolation vB_KpnM_KpVB3, a phage demonstrating potential therapeutic efficacy against infections caused by CRKP.

Background: Klebsiella pneumoniae (KP) is the second most prevalent Gram-negative bacterium causing bloodstream infections (BSIs). In recent years, the management of BSIs caused by KP has become increasingly complex due to the emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP). Although numerous studies have explored the risk factors for the development of CRKP-BSIs, the mortality of patients with KP-BSIs, and the molecular epidemiological characteristics of CRKP, the variability in data across different populations, countries, and hospitals has led to inconsistent conclusions. In this single-center retrospective observational study, we utilized logistic regression analyses to identify independent risk factors for CRKP-BSIs and factors associated with mortality in KP-BSI patients. Furthermore, a risk factor-based prediction model was developed. CRKP isolates underwent whole-genome sequencing (WGS), followed by an evaluation of microbiological characteristics, including antimicrobial resistance and virulence genes, as well as epidemiological characteristics and phylogenetic analysis. Results: Our study included a total of 134 patients with KP-BSIs, comprising 50 individuals infected with CRKP and 84 with carbapenem-susceptible Klebsiella pneumoniae (CSKP). The independent risk factors for CRKP-BSIs were identified as gastric catheterization (OR = 9.143; CI = 1.357–61.618; P = 0.023), prior ICU hospitalization (OR = 4.642; CI = 1.312–16.422; P = 0.017), and detection of CRKP in non-blood sites (OR = 8.112; CI = 2.130-30.894; P = 0.002). Multivariate analysis revealed that microbiologic eradication after 6 days (OR = 3.569; CI = 1.119–11.387; P = 0.032), high Pitt bacteremia score (OR = 1.609; CI = 1.226–2.111; P = 0.001), and inappropriate empirical treatment after BSIs (OR = 6.756; CI = 1.922–23.753; P = 0.003) were independent risk factors for the 28-day mortality in KP-BSIs. The prediction model confirmed that microbiologic eradication after 6.5 days and a Pitt bacteremia score of 4.5 or higher were significant predictors of the 28-day mortality. Bioinformatics analysis identified ST11 as the predominant CRKP sequence type, with blaKPC−2 as the most prevalent gene variant. CRKP stains carried multiple plasmid-mediated resistance genes along with some virulence genes. Phylogenetic analysis indicated the presence of nosocomial transmission of ST11 CRKP within the ICU. Conclusions: The analysis of risk factors for developing CRKP-BSIs and the association between KP-BSIs and 28-day mortality, along with the development of a risk factor-based prediction model and the characterization of CRKP strains, enhances clinicians' understanding of the pathogens responsible for BSIs. This understanding may help in the timely administration of antibiotic therapy for patients with suspected KP-BSIs, potentially improving outcomes. [ABSTRACT FROM AUTHOR]

Background: Klebsiella pneumoniae is the most commonly encountered pathogen in clinical practice. Widespread use of broad-spectrum antibiotics has led to the current global dissemination of carbapenem-resistant K. pneumoniae, which poses a significant threat to antibacterial treatment efficacy and public health. Outer membrane vesicles (OMVs) have been identified as carriers capable of facilitating the transfer of virulence and resistance genes. However, the role of OMVs in carbapenem-resistant K. pneumoniae under external pressures such as antibiotic and phage treatments remains unclear. Methods: To isolate and purify OMVs under the pressure of phages and tigecycline, we subjected K. pneumoniae 0692 harboring plasmid-mediated blaNDM-1 and blaKPC-2 genes to density gradient separation. The double-layer plate method was used to isolate MJ1, which efficiently lysed K. pneumoniae 0692 cells. Transmission electron microscopy (TEM) was used to characterize the isolated phages and extract OMV groups for relevant morphological identification. Determination of protein content of each OMV group was conducted through bicinchoninic acid assay (BCA) and proteomic analysis. Results: K. pneumoniae 0692 released OMVs in response to different environmental stimuli, which were characterized through TEM as having the typical structure and particle size of OMVs. Phage or tigecycline treatment alone resulted in a slight increase in the mean protein concentration of OMVs secreted by K. pneumoniae 0692 compared to that in the untreated group. However, when phage treatment was combined with tigecycline, there was a significant reduction in the average protein concentration of OMVs compared to tigecycline treatment alone. Proteomics showed that OMVs encapsulated numerous functional proteins and that under different external stresses of phages and tigecycline, the proteins carried by K. pneumoniae 0692-derived OMVs were significantly upregulated or downregulated compared with those in the untreated group. Conclusions: This study confirmed the ability of OMVs to carry abundant proteins and highlighted the important role of OMV-associated proteins in bacterial responses to phages and tigecycline, representing an important advancement in microbial resistance research. [ABSTRACT FROM AUTHOR]

Objective To explore the risk factors and clinical prognosis of patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) bloodstream infection in hospital, and provide a scientific basis for the effective control of CRKP bloodstream infection. Methods Adopting a case-control study in a 1∶2 ratio, cases of CRKP bloodstream infection in Guangdong Provincial People′s Hospital from January 2012 to December 2022 were collected and analyzed through retrospective analysis. Based on the results of the blood culture for 28 days, the CRKP group was divided into a survival group and a death group. Meanwhile, univariate and multivariate logistics regression were applied to analyze the related risk factors of CRKP bloodstream infection and the important risk factors affecting the prognosis of CRKP bloodstream infection in 28 days. Kalan-Meier was employed to plot the survival curve.Results Central venous intubation (P=0.042), other site infections (P=0.028), and previous use of antibiotics (P＜0.001) may be important risk factors for CRKP bloodstream infection in the hospital. Cardiovascular and cerebrovascular diseases (P=0.029) were the main risk factors for patients infected with CRKP dead in 28 days, and the death rate of patients in the CRKP group was significantly higher than that in the carbapenem-sensitive Klebsiella pneumoniae (CSKP) group (P＜0.001）. Conclusion The high fatality rate of CRKP bloodstream infection seriously affects the prognosis of patients. Hence, the clinic should endeavor to protect patients from infection, reduce the occurrence of CRKP bloodstream infection, and curb the spread of CRKP in hospital. [ABSTRACT FROM AUTHOR]

The widespread dissemination of carbapenem-resistant Klebsiella pneumoniae (CRKP) and its drug resistance transfer poses a global public health threat. While previous studies outlined CRKP's drug resistance mechanism, there is limited research on strategies inhibiting CRKP drug resistance spread. This study investigates the potential of Bifidobacterium longum (B. longum) FB1-1, a probiotic, in curbing the spread of drug resistance among CRKP by evaluating its cell-free supernatant (CFS) for antibacterial activity. Evaluating the inhibitory effect of FB1-1 CFS on CRKP drug resistance spread involved analyzing its impact on drug resistance and virulence gene expression; drug resistance plasmid transfer FB1-1 CFS exhibited an MIC range of 125 μL/mL against CRKP. After eight hours of co-culture, CFS achieved a 96% and 100% sterilization rate at two and four times the MIC, respectively. At sub-inhibitory concentrations (1/2× MIC), FB1-1 CFS reduced the expression of the bla_KPC gene, which is pivotal for carbapenem resistance, by up to 62.13% across different CRKP strains. Additionally, it markedly suppressed the expression of the uge gene, a key virulence factor, by up to 91%, and the fim_H gene, essential for bacterial adhesion, by up to 53.4%. Our study primarily focuses on determining the inhibitory effect of FB1-1 CFS on CRKP strains harboring the bla_KPC gene, which is a critical resistance determinant in CRKP. Furthermore, FB1-1 CFS demonstrated the ability to inhibit the transfer of drug resistance plasmids among CRKP strains, thus limiting the horizontal spread of resistance genes. This study highlights FB1-1 CFS's inhibitory effect on CRKP drug resistance spread, particularly in strains carrying the bla_KPC gene, thus offering a novel idea and theoretical foundation for developing antibacterial drugs targeting CRKP resistance. [ABSTRACT FROM AUTHOR]

With the increasing burden of carbapenem-resistant Klebsiella pneumoniae (CR-Kp), including high rates of healthcare-associated infections, treatment failure, and mortality, a good therapeutic strategy for attacking this multi-resistant pathogen is one of the main goals in current medical practice and necessitates the use of novel antibiotics or new drug combinations. Objectives: We reviewed the clinical and microbiological outcomes of seven patients treated at the "Agrippa Ionescu" Clinical Emergency Hospital between October 2023 and January 2024, aiming to demonstrate the synergistic activity of the ceftazidime–avibactam (C/A) plus aztreonam (ATM) combination against the co-producers of blaNDM + blaOXA-48-like CR-Kp. Material and Methods: Seven CR-Kp with blaNDM and blaOXA-48 as resistance mechanisms were tested. Seven patients treated with C/A + ATM were included. The synergistic activity of C/A + ATM was proven through double-disk diffusion in all seven isolates. Resistance mechanisms like KPC, VIM, OXA-48, NDM, IMP, and CTX-M were assessed through immunochromatography. Results: With a mean of nine days of treatment with the synergistic combination C/A + ATM, all patients achieved clinical recovery, and five achieved microbiological recovery. Conclusions: With the emerging co-occurrence of blaOXA-48 and blaNDM among Kp in Romania, the combination of C/A and ATM could be a promising therapeutic option. [ABSTRACT FROM AUTHOR]

The global emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has become a critical public healthcare concern due to treatment challenges and high mortality. In recent years, there has been an increase in cases of CRKP co-producing New Delhi metallo-β-lactamases (NDM) and oxacillinase 48 (OXA-48)-like carbapenemases in the US. The aim of this study was to correlate the clinical and genomic characteristics of CRKP co-producing NDM and OXA-48-like carbapenemases isolated from patients in Southern California since 2016. Whole-genome sequencing was performed on clinical isolates obtained from various sources, including blood, abdominal fluid, wounds, and urine. Genetic diversity was observed in these CRKP, including ST-14, ST-16, ST-167, ST-437, ST-2096, and ST-2497 lineages. Phylogenetic analysis revealed two closely related clusters (ST-14 and ST-2497), with single nucleotide polymorphism (SNP) differences ranging from 0 to 36, suggesting a possible local spread of these CRKP. Significant antimicrobial resistance (AMR) genes were identified in these CRKP, including blaNDM-1, blaNDM-5, blaOXA-232, blaOXA-181, blaCTX-M-15, armA, tet(A), and tet(D). Moreover, pColKP3-type and Inc-type plasmids known to harbor AMR genes were also detected in these isolates. Most of the patients infected with this rare type of CRKP died, although their severe comorbidities also played important roles in their demise. Our study highlighted the extremely limited treatment options and poor clinical outcomes associated with these dual-carbapenemase-producing CRKP. Real-time genomic surveillance of these unusual and deadly CRKP can provide critical information for infection prevention and treatment guidance.

ABSTRACT Colistin is used as a last-line therapy against carbapenem-resistant Klebsiella pneumoniae (CRKP). However, colistin resistance in Klebsiella pneumoniae is increasingly reported worldwide. This study aims to investigate the instrumental role of insertion sequence (IS) elements in colistin resistance through mgrB disruption in K. pneumoniae during treatment. Five clinical isolates of CRKP, designated KPN1~KPN5 were collected from the lower respiratory tract of a patient with chest infection before and after treatment with colistin. Antimicrobial susceptibility testing was performed using the broth microdilution method. Whole genome sequencing and bioinformatics were used to analyze the sequence types (STs), resistance genes, and genetic characteristics of the five isolates of K. pneumoniae. Antimicrobial susceptibility testing indicated that all five K. pneumoniae isolates were resistant to cephalosporins (ceftriaxone, ceftazidime, and cefepime), several carbapenems (imipenem, meropenem), cefoperazone–sulbactam, piperacillin–tazobactam, ciprofloxacin, and fosfomycin, whereas they were sensitive to amikacin and tigecycline. In addition, three of these isolates were resistant to colistin, with minimum inhibitory concentration values of >8 mg/L. Whole genome sequencing revealed that all five K. pneumoniae isolates belonged to sequence type 1 (ST1), which shared an identical blaKPC-2. Notably, disruption of mgrB by the ISKpn26 insertion sequence was shown to be the primary colistin resistance mechanism during the treatment. To our knowledge, this is the first report of ISKpn26 element mediating mgrB disruption in the ST1 colistin and CRKP obtained from a patient with chest infection in mainland China. This study provides new research ideas to explore the clinical drug resistance mechanism of CRKP and the critical need to monitor and understand resistance mechanisms to preserve the efficacy of last-line antibiotics such as colistin.IMPORTANCEOf note, this chapter gives an update on colistin resistance in sequence type 1 Klebsiella pneumoniae, by focusing on the mgrB disrupted by ISKpn26 element.

ABSTRACT The global rise of antibiotic resistance has renewed interest in phage therapy, as an alternative to antibiotics to eliminate multidrug-resistant (MDR) bacterial pathogens. However, optimizing the broad-spectrum efficacy of phage therapy remains a challenge. In this study, we addressed this issue by employing strategies to improve antimicrobial efficacy of phage therapy against MDR Klebsiella pneumoniae strains, which are notorious for their resistance to conventional antibiotics. This includes the selection of broad host range phages, optimization of phage formulation, and combinations with last-resort antibiotics. Our findings unveil that having a broad host range was a dominant trait of isolated phages, and increasing phage numbers in combination with antibiotics significantly enhanced the suppression of bacterial growth. The decreased incidence of bacterial infection was explained by a reduction in pathogen density and emergence of bacterial resistance. Furthermore, phage-antibiotic synergy (PAS) demonstrated considerable broad-spectrum antibacterial potential against different clades of clinical MDR K. pneumoniae pathogens. The improved treatment outcomes of optimized PAS were also evident in a murine model, where mice receiving optimized PAS therapy demonstrated a reduced bacterial burden in mouse tissues. Taken together, these findings offer an important development in optimizing PAS therapy and its efficacy in the elimination of MDR K. pneumoniae pathogens.IMPORTANCEThe worldwide spread of antimicrobial resistance (AMR) has posed a great challenge to global public health. Phage therapy has become a promising alternative against difficult-to-treat pathogens. One important goal of this study was to optimize the therapeutic efficiency of phage-antibiotic combinations, known as phage-antibiotic synergy (PAS). Through comprehensive analysis of the phenotypic and genotypic characteristics of a large number of CRKp-specific phages, we developed a systematic model for phage cocktail combinations. Crucially, our finding demonstrated that PAS treatments not only enhance the bactericidal effects of colistin and tigecycline against multidrug-resistant (MDR) K. pneumoniae strains in in vitro and in vivo context but also provide a robust response when antibiotics fail. Overall, the optimized PAS therapy demonstrates considerable potential in combating diverse K. pneumoniae pathogens, highlighting its relevance as a strategy to mitigate antibiotic resistance threats effectively.

ABSTRACT: Objectives: Pyogenic liver abscess (PLA) is a severe and potentially fatal infectious disease. Klebsiella pneumoniae (K. pneumoniae) is the predominant pathogen responsible for PLA. This study aims to investigate the clinical characteristics and prognostic factors of K. pneumoniae–induced pyogenic liver abscess (KP-PLA), particularly those caused by carbapenem-resistant K. pneumoniae (CRKP). Methods: Analyses were performed on PLA patients from January 2010 to December 2021, to investigate the differences of K. pneumoniae from other etiologically infected PLA patients. Univariate and multivariate logistic regression analyses were used to compare prognostic factors between patients with carbapenem-resistant K. pneumoniae PLA (CRKP-PLA) and patients with carbapenem-sensitive K. pneumoniae PLA. Results: Univariate analysis demonstrated a significant association between KP-PLA and factors including diabetes mellitus (P < 0.001), cholecystitis and cholelithiasis (P = 0.032), single abscess (P = 0.016), and abscesses with a diameter over 50 mm (P = 0.004). The CRKP group exhibited a higher prevalence of therapeutic interventions before K. pneumoniae infection, including abdominal surgery, mechanical ventilation, sputum suction, tracheal cannula, routine drainage of the abdominal cavity, and peripherally inserted central venous catheters (P < 0.05). Multivariate logistic regression analysis revealed that admission to the intensive care unit was an independent risk factor associated with CRKP-PLA (odds ratio 36; 95% confidence interval 1.77–731.56; P = 0.020). Conclusion: The KP-PLA patients were significantly associated with diabetes and were more likely to have single abscesses larger than 50 mm. PLA patients with a history of admission to intensive care unit or invasive therapeutic procedures should be given special consideration if combined with CRKP infection.

Purpose Infection by carbapenem-resistant Klebsiella pneumoniae (CRKP) has high mortality. There is no clear optimal therapeutic choice for pneumonia caused by CRKP. The aim of this study was to compare the clinical outcomes and safety of the standard doses of polymyxin B-based regimens vs tigecycline-based regimens and to identify risk factors for mortality.Methods This retrospective cohort study included patients with pneumonia caused by CRKP between January 1, 2020 and December 31, 2022. The primary outcomes were 7-day bacterial eradication rate and 14- and 28-day all-cause mortality. The secondary outcome was incidence of acute kidney injury.Results Seventy-three patients were included in this study, 29 in the polymyxin B-based combination therapy group and 44 in tigecycline-based combination therapy group. There were no significant differences between the two groups in terms of the 7-day bacterial eradication rate (31.03% vs 20.45%, p = 0.409), the 14-day all-cause mortality (37.93% vs 22.73%, p = 0.160), and the incidence of acute kidney injury (14.29% vs 6.82%, p = 0.526). The 28-day all-cause mortality in the polymyxin B-based therapy group was higher than in the tigecycline-based group (75.86% vs 45.45%, p = 0.010). Binary logistic regression analysis revealed that male and previous use of carbapenems were independent factors associated with 28-day all-cause mortality for patients treated with polymyxin B (p

Despite no carbapenem use in food animals, carbapenem-resistant Klebsiella pneumoniae (CRKP) perseveres within food animals, rising significant concerns regarding public health risks originating from these non-clinical reservoirs. To investigate the potential link between CRKP in food animals and its infections in humans, we conducted a cross-sectional study encompassing human clinical, meat products, and farm animals, in Qingdao city, Shandong province, China. We observed a relatively higher presence of CRKP among hospital inpatients (7.3%) compared to that in the meat products (2.7%) and farm animals (pig, 4.6%; chicken, 0.63%). Multilocus sequence typing and core-genome phylogenetic analyses confirm there is no evidence of farm animals and meat products in the clinical acquisition of K. pneumoniae isolates and carbapenem-resistant genes. However, potential transmission of K. pneumoniae of ST659 and IncX3 plasmid harbouring blaNDM-5 gene from pigs to pork and farm workers was observed. Our findings suggest a limited role of farm animals and meat products in the human clinical acquisition of K. pneumoniae, and the transmission of K. pneumoniae is more common within settings, than between them.

ABSTRACTCarbapenem-resistant Klebsiella pneumoniae (CR-Kp) is a significant threat to public health worldwide. The primary reservoir for CR-Kp is the intestinal tract. There, the bacterium is usually present at low density but can bloom following antibiotic treatment, mostly in hospital settings. The impact of disturbances in the intestinal environment on the fitness, survival, expansion, and drug susceptibility of this pathogen is not well-understood, yet it may be relevant to devise strategies to tackle CR-Kp colonization and infection. Here, we adopted an in vivo model to examine the transcriptional adaptation of a CR-Kp clinical isolate to immune activation in the intestine. We report that as early as 6 hours following host treatment with anti-CD3 antibody, CR-Kp underwent rapid transcriptional changes including downregulation of genes involved in sugar utilization and amino acid biosynthesis and upregulation of genes involved in amino acid uptake and catabolism, antibiotic resistance, and stress response. In agreement with these findings, treatment increased the concentration of oxidative species and amino acids in the mouse intestine. Genes encoding for proteins containing the domain of unknown function (DUF) 1471 were strongly upregulated, however their deletion did not impair CR-Kp fitness in vivo upon immune activation. Transcription factor enrichment analysis identified the global regulator cAMP-Receptor Protein, CRP, as a potential orchestrator of the observed transcriptional signature. In keeping with the recognized role of CRP in regulating utilization of alternative carbon sources, crp deletion in CR-Kp resulted in strongly impaired gut colonization, although this effect was not amplified by immune activation. Thus, following intestinal colonization, which occurs in a CRP-dependent manner, CR-Kp can rapidly respond to immune cues by implementing a well-defined and complex transcriptional program whose direct relevance toward bacterial fitness warrants further investigation. Additional analyses utilizing this model may identify key factors to tackle CR-Kp colonization of the intestine.

ABSTRACTTo investigate the epidemiology of ST20 carbapenem-resistant Klebsiella pneumoniae (CRKP) in China, and further explore the genomic characteristics of blaIMP-4 and blaNDM-1 coharboring isolates and plasmid contributions to resistance and fitness. Seven ST20 CRKP isolates were collected nationwide, and antimicrobial susceptibility testing was performed. Antimicrobial resistance genes, virulence genes, and plasmid replicons were identified via whole-genome sequencing, and clonality assessed via core-genome multilocus sequence typing. Furthermore, we found four dual-metallo-β-lactamases (MBL)-harbouring isolates, the gene location was detected by Southern blotting, and plasmid location analysis showed that blaIMP-4 was located on a separate plasmid, a self-conjugative fusion plasmid, or the bacterial chromosome. These isolates were subjected to long-read sequencing, the presence of blaIMP-4 in different locations was identified by genomic comparison, and transposon units were detected via inverse PCR. We subsequently found that blaIMP-4 on the fusion plasmid and bacterial chromosome was formed via intact plasmid recombination by the IS26 and ltrA, respectively, and the circular transposon unit was related to cointegration, however, blaIMP-4 in different locations did not affect the gene stability. The blaNDM-1-harbouring plasmid contributed to the increased resistance to β-lactams and shortened survival lag time which was revealed in plasmid cured isolates. In summary, the K. pneumoniae ST20 clone is a high-risk resistant clone. With the use of ceftazidime/avibactam, MBL-positive isolates, especially dual-MBL-harbouring isolates, should be given additional attention.

Background: Ceftazidime-avibactam is a treatment option for carbapenemresistant gram-negative bacilli (CR-GNB) infections. However, the risk factors associated with ceftazidime-avibactam (CAZ-AVI) treatment failure in kidney transplant (KT) recipients and the need for CAZ-AVI-based combination therapy remain unclear. Methods: From June 2019 to December 2023, a retrospective observational study of KT recipients with CR-GNB infection treated with CAZ-AVI was conducted, with the primary outcome being 30-day mortality and secondary outcomes being clinical cure, microbiological cure, and safety. Risk factors for 30-day mortality and clinical failure were also investigated. Results: A total of 81 KT recipients treated with CAZ-AVI were included in this study. Forty recipients (49.4%) received CAZ-AVI monotherapy, with a 30-day mortality of 22.2%. The clinical cure and microbiological cure rates of CAZ/AVI therapy were 72.8% and 66.7%, respectively. CAZ-AVI alone or in combination with other medications had no effect on clinical cure or 30-day mortality. Multivariate logistic regression analysis revealed that a higher Acute Physiology and Chronic Health Evaluation (APACHE) II score (odds ratio [OR]: 4.517; 95% confidence interval [CI]: 1.397-14.607; P = 0.012) was an independent risk factor for 30-day mortality. Clinical cure was positively associated with the administration of CAZ-AVI within 48 hours of infection onset (OR: 11.009; 95% CI: 1.344-90.197; P=0.025) and negatively associated with higher APACHE II scores (OR: 0.700; 95% CI: 0.555-0.882; P=0.002). Four (4.9%) recipients experienced recurrence within 90 days after the initial infection, 3 (3.7%) recipients experienced CAZ-AVI-related adverse events, and no CAZ-AVI resistance was identified. Conclusion: CAZ-AVI is an effective medication for treating CR-GNB infections following kidney transplantation, even as monotherapy. Optimization of CAZ/AVI therapy (used within 48 hours of infection onset) is positively associated with potential clinical benefit. Further larger-scale studies are needed to validate these findings. [ABSTRACT FROM AUTHOR]

Objective To evaluate the effectiveness of multi-disciplinary team (MDT) mode in the prevention and control of multidrug resistant organism (MDRO) infection in lung transplant recipients. Methods Lung transplant recipients admitted to the hospital from 2019 to 2022 were enrolled. MDT expert group was established in January, 2020. A series of prevention and control measures were conducted. The implementation rate of MDRO prevention and control measures and the detection rate of MDRO on the environmental surface from 2020 to 2022, and the detection rate of MDRO in lung transplant recipients from 2019 to 2022 were analyzed. Results The overall implementation rate of MDRO prevention and control measures for medical staff was increased from 64.9% in 2020 to 91.6% in 2022, showing an increasing trend year by year (P<0.05). The detection rate of MDRO on the environmental surface was decreased from 28% in 2020 to 9% in 2022, showing a downward trend year by year (P<0.05). The detection rate of MDRO in lung transplant recipients was decreased from 66.7% in 2019 to 44.3% in 2022, showing a decreasing trend year by year (P<0.001). Conclusions MDT mode management may enhance the implementation of MDRO prevention and control measures for medical staff, effectively reduce the infection rate of MDRO in lung transplant recipients and the detection rate of MDRO on the environmental surface, which is worthy of widespread application. [ABSTRACT FROM AUTHOR]

Background: The antimicrobial resistance (AMR) of Klebsiella pneumoniae recorded a steep upward trend over the last two decades, among which carbapenem-resistant Klebsiella pneumoniae (CRKP) is one of the most concerning strains considering the development and spread of AMR. The aim of this study was to analyze the evolution of AMR for Klebsiella pneumoniae and to describe the risk factors of AMR for Klebsiella pneumoniae, including the COVID-19 pandemic. Methods: We conducted a retrospective study on Klebsiella pneumoniae non-duplicative isolates collected from patients admitted to a tertiary hospital in Bucharest, Romania, from January 2019 to December 2021. We evaluated AMR changes by comparing resistance between 2019 and the mean of 2020–2021. Results: The rates of AMR increased for third-generation cephalosporins, carbapenems, aminoglycosides, fluoroquinolones, and colistin and decreased for trimethoprim/sulfamethoxazole (TMP/SMX), 45.7% in 2019 vs. 28.3% in 2021. A longer length of hospital stay (ꭓ2 = 49.68, p < 0.01); recent antibiotic consumption, RR = 1.38, 95% CI [1.21, 1.57]; and recent contact with hospital settings, RR = 1.54, 95% CI [1.32, 1.8] were risk factors for multidrug-resistant (MDR) Klebsiella pneumoniae. Conclusions: The AMR of Klebsiella pneumoniae increased during 2020–2021 for most of the potential active antibiotics; only TMP/SMX resistance decreased, and it may represent a treatment option for CRKP or MDR Klebsiella pneumoniae infections. Decreasing the excessive use of antibiotics and the implementation of prevention and control measures in healthcare settings are mandatory for avoiding further increases in the AMR rate of Klebsiella pneumoniae. [ABSTRACT FROM AUTHOR]

Background: Carbapenem-resistant Klebsiella pneumoniae (Cr-Kpn) is becoming a growing public health problem through the failure of adequate treatment. This study's objectives are to describe the sources of Cr-Kpn in our hospital over 22 months, associating factors with the outcome of Cr-Kpn-positive patients, especially those with NDM+OXA-48-like (New Delhi Metallo-β-Lactamase and oxacillinase-48), and the effectiveness of the treatments used. Methods: A retrospective observational cohort study including all hospitalized patients with Cr-Kpn isolates. We reported data as percentages and identified independent predictors for mortality over hospital time through multivariate analysis. Results: The main type of carbapenemases identified were NDM+OXA-48-like (49.4%). The statistical analysis identified that diabetes and co-infections with the Gram-negative, non-urinary sites of infection were factors of unfavorable evolution. The Cox regression model identified factors associated with a poor outcome: ICU admission (HR of 2.38), previous medical wards transition (HR of 4.69), and carbapenemase type NDM (HR of 5.98). We did not find the superiority of an antibiotic regimen, especially in the case of NDM+OXA-48-like. Conclusions: The increase in the incidence of Cr-Kpn infections, especially with NDM+OXA-48-like pathogens, requires a paradigm shift in both the treatment of infected patients and the control of the spread of these pathogens, which calls for a change in public health policy regarding the use of antibiotics and the pursuit of a One Health approach. [ABSTRACT FROM AUTHOR]

AbstractThe main aim of this study was to compare and analyze the effectiveness of treatment regimens using ceftazidime/avibactam (CAZ/AVI) versus fosfomycin plus meropenem (FOS/MER) for managing bloodstream infections (BSI) or ventilator-associated pneumonia (VAP) caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) in critically ill patients. Between 4 January 2019, and 16 July 2023, adult patients (≥18 years old) diagnosed with BSI or VAP due to culture confirmed CRKP in ICU of a tertiary care hospital were investigated retrospectively. A total of 71 patients were categorized into two groups: 30 patients in CAZ/AVI-based, and 41 patients in FOS/MER-based group. No substantial disparities were found in the total duration of ICU hospitalization, as well as the 14- and 30-day mortality rates, between patients treated with CAZ/AVI-based and FOS/MER-based therapeutic regimens. We consider that our study provides for the first time a comprehensive understanding of treatment outcomes and associated risk factors among patients with CRKP-related infections. [ABSTRACT FROM AUTHOR]

Eravacycline (ERV) has emerged as a therapeutic option for the treatment of carbapenem-resistant pathogens. However, the advent of heteroresistance (HR) to ERV poses a challenge to these therapeutic strategies. This study aimed to investigate ERV HR prevalence among common clinical isolates and further characterize ERV HR in carbapenem-resistant Klebsiella pneumoniae (CRKP). A total of 280 clinical pathogens from two centers were selected for HR and analyzed using population analysis profiling (PAP) and modified E-tests. The PAP assay revealed an overall ERV HR prevalence of 0.7% (2/280), with intermediate heterogeneity observed in 24.3% (68/280) of strains. The proportion of heteroresistant strains was 18.3% according to modified E-test results. A time-killing assay demonstrated that CRKP CFU increased significantly after 10 h of ERV treatment, contributing to the reduced bactericidal effect of ERV in vitro. Interestingly, dual treatment with ERV and polymyxin B effectively inhibited the total CFU, simultaneously reducing the required polymyxin B concentration. Furthermore, fitness cost measurements revealed a growth trade-off in CRKP upon acquiring drug resistance, highlighting fitness costs as crucial factors in the emergence of ERV HR in CRKP. Overall, the findings of the current study suggest that ERV HR in clinical strains presents a potential obstacle in its clinical application. [ABSTRACT FROM AUTHOR]

Introduction: Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections commonly cause hospital-acquired infections. The study aimed to compare the outcomes of CRKP infections between patients receiving ceftazidime avibactam +/− aztreonam and polymyxins in a hospital setting with a high prevalence of New Delhi Metallo Beta Lactamase production. Methods: We conducted a retrospective cohort study from January 2020 to September 2022 in critically ill adult patients admitted to a non-COVID-19 medical intensive care unit with CRKP infection. The patients were followed up for a total of 30 days or death, whichever was later. Results: Of a total of 106 patients included in the study, 65 patients received polymyxins and 41 patients received ceftazidime–avibactam +/− aztreonam. Higher 30-day mortality was noted in the polymyxin group (56.9% vs. 29.2%, P = 0.005). The mean time to event (mortality) in ceftazidime–avibactam +/− aztreonam was 23.9 + 1.5 days which was significantly higher compared to polymyxins (17.9 + 1.2 days, p = 0.006). On Cox regression analysis, after adjusting for the covariates, the hazard ratio for time to event with the use of polymyxin was 2.02 (95% CI: 1.03–3.9). Conclusion: Ceftazidime–avibactam + aztreonam is possibly associated with better clinical outcomes in patients infected with CRKP. [ABSTRACT FROM AUTHOR]

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) clinical isolations have rapidly increased in pediatric patients. To investigate a possible health care-associated infections of CRKP in a tertiary pediatric hospital, the circulating clones and carbapenem-resistant pattern between CRKP and carbapenem-resistant Acinetobacter baumannii (CRAB) isolates were compared to classify their epidemiological characteristics. The results will help to identify the epidemic pattern of the CRKP transmission in the hospital. Methods: Ninety-six CRKP and forty-eight CRAB isolates were collected in Kunming Children's Hospital from 2019 through 2022. These isolates were genotyped using repetitive extragenic palindromic-PCR (REP-PCR). Carbapenemase phenotypic and genetic characterization were investigated using a disk diffusion test and singleplex PCR, respectively. In addition, these characteristics of the two pathogens were compared. Conclusions: These CRKP isolates exhibited different biological and genetic characteristics with dynamic changes, suggesting widespread communities. Continuous epidemiological surveillance and multicenter research should be carried out to strengthen the prevention and control of infections. [ABSTRACT FROM AUTHOR]

Isolates coproducing serine/metallo-carbapenems are a serious emerging public health threat, given their rapid dissemination and the limited number of treatment options. The purposes of this study were to evaluate the in vitro antibacterial activity of novel β-lactam-β-lactamase inhibitor combinations (BLBLIs) against carbapenem-resistant Klebsiella pneumoniae (CRKP) coproducing metallo-β-lactamase and serine-β-lactamase, and to explore their effects in combination with aztreonam, meropenem, or polymyxin in order to identify the best therapeutic options. Four CRKP isolates coproducing K. pneumoniae carbapenemase (KPC) and New Delhi metallo-β-lactamase (NDM) were selected, and a microdilution broth method was used to determine their susceptibility to antibiotics. Time-kill assay was used to detect the bactericidal effects of the combinations of antibiotics. The minimum inhibitory concentration (MIC) values for imipenem and meropenem in three isolates did not decrease after the addition of relebactam or varbobactam, but the addition of avibactam to aztreonam reduced the MIC by more than 64-fold. Time-kill assay demonstrated that imipenem-cilastatin/relebactam (ICR) alone exerted a bacteriostatic effect against three isolates (average reduction: 1.88 log10 CFU/mL) and ICR combined with aztreonam exerted an additive effect. Aztreonam combined with meropenem/varbobactam (MEV) or ceftazidime/avibactam (CZA) showed synergistic effects, while the effect of aztreonam combined with CZA was inferior to that of MEV. Compared with the same concentration of aztreonam plus CZA combination, aztreonam/avibactam had a better bactericidal effect (24 h bacterial count reduction >3 log10CFU/mL). These data indicate that the combination of ATM with several new BLBLIs exerts powerful bactericidal activity, which suggests that these double β-lactam combinations might provide potential alternative treatments for infections caused by pathogens coproducing-serine/metallo-carbapenems. [ABSTRACT FROM AUTHOR]

Klebsiella pneumoniae is one of the main opportunistic pathogens that cause a broad spectrum of diseases with increasingly frequent acquisition of resistance to antibiotics, namely carbapenems. This study focused on the characterization of 23 OXA-48-like carbapenemase-producing K. pneumoniae isolates using phenotypic and molecular tests. Phenotypic determination of the presence of β-lactamases was performed using the extended-spectrum beta-lactamase (ESBL) NP test, and phenotypic determination of the presence of carbapenemase was based on the Carba NP test. Antimicrobial susceptibility tests were performed to assess the resistance against carbapenems. Molecular characterization of ESBL genes and carbapenemase genes (blaOXA-48, blaKPC, blaVIM, and blaNDM) was performed using polymerase chain reaction (PCR) techniques. In addition, K. pneumoniae strains were analyzed for their relatedness using multilocus sequence typing PCR analysis based on the Institut Pasteur protocol, which produces allelic profiles that contain their evolutionary and geographic pattern. Following further Sanger sequencing of the blaOXA-48 genes, no genetic mutations were found. Some OXA-48-producing K. pneumoniae isolates coharbored blaKPC, blaNDM, and blaVIM genes, which encode other carbapenemases that can hydrolyze carbapenem antibiotics. The final part of the study focused on the characterization of the plasmid profiles of all isolates to better understand the spreading of the IncL/M blaOXA-48 plasmid gene. The plasmid profile also revealed other incompatibility groups, suggesting that other plasmid genes are spreading in K. pneumoniae isolates, which can coharbor and spread different carbapenemases simultaneously. [ABSTRACT FROM AUTHOR]

Carbapenem-resistant Klebsiella pneumoniae (CRKp) is a major pathogen causing nosocomial infections with a high mortality and poor prognosis. Gastrointestinal carriage has been acknowledged as the primary reservoir of CRKp infections. To explore the incidence and risk factors associated with CRKp infection following colonization. The PubMed, Web of Science, and Cochrane Library databases were searched for relevant articles published between December 1998 and June 2023. Pooled estimates with a 95% confidence interval (CI) were calculated for the incidence rate, whereas pooled odds ratios (ORs) were calculated for the risk factors for which the OR was reported in three or more studies. Fourteen studies were included in the review with 5483 patients for the assessment of incidence, whereas seven of these studies with 2170 patients were included for the analysis of risk factors. In the meta-analysis, the incidence of CRKp infections after colonization was 23.2% (17.9–28.5). Additionally, three independent risk factors for subsequent CRKp infections were identified as admission to the intensive care unit (ICU) (2.59; 95% CI: 1.64–4.11), invasive procedures (2.53; 95% CI: 1.59–4.03), and multi-site colonization (6.24; 95% CI: 2.38–16.33). This review reveals the incidence of CRKp infections in rectal carriers in different countries, emphasizing the role of rectal colonization with CRKp as an important source of nosocomial infections. Significantly, the risk factors indicated in this review can assist clinicians in identifying CRKp carriers with an elevated risk of subsequent infections, thereby enabling further measures to be taken to prevent nosocomial infections. [ABSTRACT FROM AUTHOR]

Carbapenems are considered to be among the last line antibiotics against extended-spectrum β-lactamase producing Enterobacterales. Carbapenem-resistant Klebsiella pneumoniae (CRKP) has been frequently reported and its spread in Europe is indisputable and poses an enormous threat to hospitalized patients which is of growing concern. This review aims to record prevalence of CRKP in the Balkan region and to review the current knowledge about this life-threatening pathogen. In this review, we summarize data about clinical isolates of carbapenem-resistant K. pneumoniae from Greece, Croatia, Romania, Bulgaria, Serbia, Slovenia, Montenegro, Bosnia-Herzegovina and Albania from published reports between 2000 and 2023. Among Balkan countries, Greece and Romania are the ones with the most reports about CRKP. Since 2007, KPCs are the dominant carbapenemases in both countries. KPC-2 and NDM-1-producing K. pneumoniae strains have been identified as the most frequent CRKP in Croatia, Bulgaria, Serbia, and Slovenia. OXA-48 enzyme has been identified in most Balkan countries. In addition, since 2018, CRKP sequence type 11 (ST11) seems to have replaced ST258 in Balkan Peninsula, while ST15 continues to thrive throughout the years. Not only efficacy of colistin against CRKP has decreased dramatically during the last ten years but colistin resistance mechanism is based on alterations of chromosomal mgrB gene, rather than the already known mcr genes. Moreover, ceftazidime-avibactam-resistant CRKP were detected mostly in Greece. Emergence of CRKP poses a severe threat to the Balkan countries. Due to the narrow therapeutic window, it is essential to prevent the spread of multiresistant K. pneumoniae strains. [ABSTRACT FROM AUTHOR]

This research focused on evaluating the clinical results of patients suffering from pneumonia caused by carbapenem-resistant Klebsiella pneumoniae (CRKP), who received treatment with either ceftazidime–avibactam (CZA) alone or in combination with other antibiotics. From January 2020 to December 2023, we retrospectively analyzed CRKP-related pneumonia patients treated in two Chinese tertiary hospitals. Mortality was measured at 14 and 30 days as the primary outcome. Secondary outcomes included the 14-day microbiological cure rate and the 14-day clinical cure rate. Factors contributing to clinical failure were evaluated via both univariate analysis and multivariate logistic regression. To account for confounding factors, propensity score matching (PSM) was utilized. Among the 195 patients with CRKP infections, 103 (52.8 %) received CZA combination therapy, and 92 (47.2 %) patients received CZA monotherapy. The combination therapy group exhibited superior clinical and microbiological cure rates compared to the monotherapy group, with a 14-day clinical cure rate of 60.1 % vs. 45.7 % (P = 0.042) and a 14-day microbiological cure rate of 72.8 % vs. 58.6 % (P = 0.038), respectively. Combination therapy reduced mortality rates at 14 days (7.8 % vs. 17.4 %, P = 0.041), but not at 30 days (14.6 % vs. 25.0 %, P = 0.066). Even after using PSM, the group treated with the CZA combination continued to had a lower mortality rate at 14 days (5.9 % vs. 17.6 %, P = 0.039). The 14-day clinical cure rate for the combination therapy group was 63.2 %, and the 14-day microbial cure rate was 77.9 %. Both of these statistics were notably greater than those observed in the monotherapy group. Furthermore, the multivariate logistic regression model indicated a significant link between combination therapy and a decrease in clinical failure. Carbapenems were noted to be the most effective class of concomitant agents. Our findings indicate that patients with pneumonia due to CRKP benefit from combination treatment of CZA rather than monotherapy; administering carbapenem in combination with CZA in the early stages could provide considerable survival benefits.

Background: The incidence of carbapenem-resistant Klebsiella pneumoniae (CRKP) infections is increasing globally. In India, around 65% of K. pneumoniae isolates are resistant to carbapenem antibiotics. The blaNDM is the predominant carbapenem-resistant gene in CRKP isolates. However, blaOXA-48 has also been reported to be increasing in recent days. Methods: K. pneumoniae strains isolated from the clinical specimens of patients attending a tertiary care hospital in Hyderabad from June 2021 to May 2022 were included in this study. Resistance to carbapenems and other antibiotics was screened using Kirby-Bauer’s disc diffusion method. Phenotypic tests such as the Carbapenemase Nordmann Poirel (CarbaNP) test, Modified Carbapenem Inactivation Method (mCIM), and EDTA Carbapenem Inactivation Method (eCIM) were used to detect the carbapenemase producers. The genes responsible for carbapenemase production were detected by the real-time polymerase chain reaction (RT-PCR) method. Results: Out of 1265 K. pneumoniae strains isolated, 241 (19 %) isolates showed resistance to any one of the carbapenem antibiotics tested. Phenotypic tests such as CarbaNP, mCIM, and eCIM revealed that 94.6 %, 97.1 %, and 95.4 % of CRKP isolates were carbapenemase producers, respectively. About 66.4 % of CRKP isolates harbored blaNDM, 17.4 % harbored blaOXA-48, and 16.2 % harbored both blaNDM and OXA-48 genes. None of the isolates tested positive for blaKPC, blaVIM, and blaIMP genes. Conclusion: In this study, blaNDM is the most prevalent carbapenemase gene in CRKP isolates. Furthermore, blaOXA-48 and the co-existence of both blaNDM and blaOXA-48 genes were also found. CRKP is emerging as a serious threat among drug-resistant bacterial pathogens which would complicate the treatment of bacterial infections with available antibiotics.

ABSTRACT This study aimed to assess the in vitro efficacy of ceftazidime-avibactam (CZA) in combination with various antimicrobial agents against carbapenem-resistant Klebsiella pneumoniae (CRKP). We selected 59 clinical CRKP isolates containing distinct drug resistance mechanisms. The minimum inhibitory concentrations (MICs) of meropenem (MEM), colistin (COL), eravacycline (ERA), amikacin (AK), fosfomycin (FOS), and aztreonam (ATM), both individually and in combination with CZA, were tested using the checkerboard method. The interactions of antimicrobial agent combinations were assessed by fractional inhibitory concentration index (FICI) and susceptible breakpoint index (SBPI). The time-kill curve assay was employed to dynamically evaluate the effects of these drugs alone and in combination format. In the checkerboard assay, the combination of CZA+MEM showed the highest level of synergistic effect against both KPC-producing and carbapenemase-non-producing isolates, with synergy rates of 91.3% and 100%, respectively. Following closely was the combination of FOS+CZA . For metallo-beta-lactamases (MBLs) producing strains, ATM+CZA displayed complete synergy, while the combination of MEM+CZA showed a synergy rate of only 57.14% for NDM-producing strains and 91.67% for IMP-producing strains. In the time-kill assay, MEM+CZA also demonstrated significant synergistic effects against the two KPC-2-producing isolates (Y070 and L70), the two carbapenemase-non-producing isolates (Y083 and L093), and the NDM-1-producing strain L13, with reductions in log10 CFU/mL exceeding 10 compared to the control. Against the IMP-producing strain Y047, ATM+CZA exhibited the highest synergistic effect, resulting in a log10 CFU/mL reduction of 10.43 compared to the control. The combination of CZA and MEM exhibited good synergistic effects against KPC-producing and non-enzyme-producing strains, followed by the FOS+CZA combination. Among MBL-producing strains, ATM+CZA demonstrated the most pronounced synergistic effect. However, the combinations of CZA with ERA, AK, and COL show irrelevant effects against the tested clinical isolates.IMPORTANCEOur study confirmed the efficacy of the combination CZA+MEM against KPC-producing and non-carbapenemase-producing strains. For metalloenzyme-producing strains, CZA+ATM demonstrated the most significant synergy. Additionally, CZA exhibited a notable synergy effect when combined with FOS. These combination therapies present promising new options for the treatment of CRKP infection.

Abstract Background Colistin and carbapenem-resistant Klebsiella pneumoniae (Col-CRKP) represent a significant and constantly growing threat to global public health. We report here an outbreak of Col-CRKP infections during the fifth wave of COVID-19 pandemic. Methods The outbreak occurred in an intensive care unit with 22 beds at a teaching university hospital, Isfahan, Iran. We collected eight Col-CRKP strains from seven patients and characterized these strains for their antimicrobial susceptibility, determination of hypermucoviscous phenotype, capsular serotyping, molecular detection of virulence and resistance genes. Clonal relatedness of the isolates was performed using MLST. Results The COVID-19 patients were aged 24–75 years with at least 50% pulmonary involvement and were admitted to the intensive care unit. They all had superinfection caused by Col-CRKP, and poor responses to antibiotic treatment and died. With the exception of one isolate that belonged to the ST11, all seven representative Col-CRKP strains belonged to the ST16. Of these eight isolates, one ST16 isolate carried the iucA and ybtS genes was identified as serotype K20 hypervirulent Col-CRKP. The bla SHV and bla NDM-1 genes were the most prevalent resistance genes, followed by bla OXA-48 and bla CTX-M-15 and bla TEM genes. Mobilized colistin-resistance genes were not detected in the isolates. Conclusions The continual emergence of ST16 Col-CRKP strains is a major threat to public health worldwide due to multidrug-resistant and highly transmissible characteristics. It seems that the potential dissemination of these clones highlights the importance of appropriate monitoring and strict infection control measures to prevent the spread of resistant bacteria in hospitals.

Background/Purpose: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is capable of causing serious community and hospital-acquired infections. However, currently, the identification of CRKP is complex and inefficient. Hence, this study aimed to develop methods for the early and effective identification of CRKP to allow reasonable antimicrobial therapy in a timely manner. Methods: K. pneumoniae (KP)-, K. pneumoniae carbapenemase (KPC)- and New Delhi metallo-β-lactamase (NDM)- specific CRISPR RNAs (crRNAs), polymerase chain reaction (PCR) primers and recombinase-aided amplification (RAA) primers were designed and screened in conserved sequence regions. We established fluorescence and lateral flow strip assays based on CRISPR/Cas13a combined with PCR and RAA, respectively, to assist in the detection of CRKP. Sixty-one clinical strains (including 51 CRKP strains and 10 carbapenem-sensitive strains) were collected for clinical validation. Results: Using the PCR-CRISPR assay, the limit of detection (LOD) for KP and the blaKPC and blaNDM genes reached 1 copy/μL with the fluorescence signal readout. Using the RAA-CRISPR assay, the LOD could reach 101 copies/μL with both the fluorescence signal readout and the lateral flow strip readout. Additionally, the positivity rates of CRKP-positive samples detected by the PCR/RAA-CRISPR fluorescence and RAA-CRISPR lateral flow strip methods was 92.16% (47/51). The sensitivity and specificity reached 100% for KP and blaKPC and blaNDM gene detection. For detection in a simulated environmental sample, 1 CFU/cm2 KP could be detected. Conclusion: We established PCR/RAA-CRISPR assays for the detection of blaKPC and blaNDM carbapenemase genes, as well as KP, to facilitate the detection of CRKP.

Lingchun Zhang,1,&ast; Yani Ma,2,&ast; Chenglong Zhao,1 Shujuan Zhao,1 Lulu Zhao,3 Yuxin Yang,4 Yuhan Wang,5 Haiyang Meng,6 Jun Sun1 1Department of Pharmacy, Henan Provincial People’s Hospital, People’s Hospital of Zhengzhou University, People’s Hospital of Henan University, Zhengzhou, People’s Republic of China; 2Department of Pharmacy, the First Affiliated Hospital of Kunming Medical University, Kunming, People’s Republic of China; 3Department of Pharmacy, Gongyi People’s Hospital, Zhengzhou, People’s Republic of China; 4Department of Pharmacy, Anyang Ophthalmic Hospital, Anyang, People’s Republic of China; 5Department of Pharmacy, Henan Integrative Medicine Hospital, Zhengzhou, People’s Republic of China; 6Department of Pharmacy, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Jun Sun, Department of Pharmacy, Henan Provincial People’s Hospital, No. 7 Weiwu Road, Zhengzhou, People’s Republic of China, Tel +86 13683827203, Email Jun_84@163.comPurpose: Carbapenem-Resistant Klebsiella pneumoniae (CRKP) is a significant public health threat, because it is associated with substantial morbidity and mortality. However, the risk factors associated with treatment failure of ceftazidime-avibactam (CAZ-AVI) and the need for CAZ-AVI-based combination remain unclear.Methods: We conducted a retrospective study of critically ill patients (age: > 18 years) diagnosed with CRKP infections and treated with CAZ-AVI for at least 24 h between June 2020 and December 2022 at Henan Provincial People’s Hospital.Results: This study included a total of 103 patients who received CAZ-AVI. Of these, 91 (88.3%) patients received the standard dosage of 2.5 g every q8h, while only 20 (19.4%) received monotherapy. The Kaplan–Meier curves showed that the all-cause 30-day mortality was significantly higher among patients who experienced septic shock than those who did not. There was no significant difference in mortality between monotherapy and combination therapy. Dose reduction of CAZ-AVI was associated with a significantly increased mortality rate. Independent risk factors for the 30-day mortality included higher APACHE II score (HR: 1.084, 95% CI: 1.024– 1.147, p = 0.005) and lower lymphocyte count (HR: 0.247, 95% CI: 0.093– 0.655, p = 0.005). Conversely, a combination therapy regimen containing carbapenems was associated with lower mortality (HR: 0.273, 95% CI: 0.086– 0.869, p = 0.028).Conclusion: Our study suggests that CAZ-AVI provides clinical benefits in terms of survival and clinical response in critically ill patients with CRKP infection. A higher APACHE II score and lower lymphocyte count were associated with 30-day mortality, while the combination therapy regimen containing carbapenems was the only protective factor. CAZ-AVI dose reduction was associated with an increased mortality rate. Futher large-scale studies are needed to validate these findings.Keywords: carbapenem-resistant Klebsiella pneumoniae, ceftazidime-avibactam, retrospective study, combination therapy

ABSTRACT: Objectives: To investigate the clinical emergence of colistin-heteroresistant, hypervirulent, and multidrug-resistant Klebsiella pneumoniae, and characterize the underlying molecular mechanisms. Methods: The population analysis profiles (PAPs) method was used to detect colistin heteroresistance. The time-killing assay was used to examine the effect of colistin on carbapenem-resistant Klebsiella pneumoniae (CRKP) in vitro. Galleria mellonella larvae infection model was used to test the potential virulence. qRT-PCR assay was conducted to compare the expression levels of efflux pump genes. Next and third-generation sequencing were conducted to analyse the genomic features. Results: Two colistin-heteroresistant isolates were detected from a multi-center carbapenem-resistant Enterobacterales (CRE) surveillance study in China, which exhibited similar survival rates as the K2 hypervirulent reference strain ATCC 43816 in a G. mellonella larvae model. The two isolates belonged to ST11, harbouring the iucABCD, iutA, iroBCD, and rpmA2 hypervirulent genes and pLVPK-like virulence plasmids. Colistin showed a weak effect on the heteroresistant strains in vitro. The efflux pump genes acrA, acrB, tolC, oqxA, and oqxB were upregulated in this subpopulation compared to the parental strains. Conclusions: This study showed the clinical emergence of colistin-heteroresistant, hypervirulent, and multidrug-resistant Klebsiella pneumoniae. AcrAB-TolC and OqxAB efflux overexpression were involved in mediating colistin heteroresistance.

Objectives: Postoperative central nervous system infections (PCNSIs) caused by carbapenem-resistant Enterobacteriaceae (CRE) frequently result in unfavourable outcomes. However, CRE PCNSIs have not been well described from a clinical and microbiological perspective. Methods: A total of 254 PCNSIs cases were included (January 2017 through June 2020), and clinical features were compared based on pathogenic classification. Cox regression analysis was performed to assess risk factors for mortality. Antibiotic susceptibility testing and whole genome sequencing were conducted on CRE isolates preserved. MLST, cgMLST, resistance genes and virulence genes were further analysed. Results: Among 254 PCNSI cases, 15.4% were caused by Enterobacteriaceae including 28 cases by CRE. The 28-day mortality rates for CRE, CSE and non-Enterobacteriaceae PCNSIs were 50.0%, 27.3%, and 7.4%, respectively. 42.9% (12/28) of the CRE PCNSIs patients achieved clinical cure, with 25.0% achieved microbiological clearance. ST11-KL64 carrying blaKPC-2 was dominant in CRE (17/23, 73.9%), and the 28-day mortality rate of its infection was 58.5%. Most CRKP carried rampA/rampA2 genes (17/23, 73.9%). Conclusion: ST11-KL64 CRKP carrying blaKPC-2 dominated among CRE PCNSIs. Targeted anti-infective combination therapy based on ceftazidime/avibactam or amikacin, combined with intrathecal administration of amikacin, was found to be effective. These findings render a new insight into the clinical and microbiological landscape of CRE PCNSIs.

Background: The human gut microbiota is an extensive population of microorganisms, and it shows significant variations between periods of optimal health and periods of illness. Vancomycin-resistant Enterococcus (VRE) and carbapenem-resistant Klebsiella pneumoniae (CRKP) are both pathogenic agents (BPAs) that can colonize in the gut after dysbiosis of microbiotal composition following antibiotic treatment. Methods: This study aimed to investigate the impact of antibiotics on the microbiotal composition of the gut. For this purpose, the first pass meconiums of 20 patients and the first rectal swabs containing BPAs of the same patients after antibiotic treatment were studied using next-generation sequencing-based 16S rRNA gene analysis. The V1–V9 region of 16S rRNA was sequenced with Oxford Nanopore. Results: Twenty-five phyla were detected in the meconiums, and 12 of them were absent after antibiotic treatment. The four most prevalent phyla in meconiums were Bacillota, Pseudomonadota, Bacteroidota, and Actinomycetota. Only the relative abundance of Pseudomonadota was increased, while a significant decrease was observed in the other three phyla (p < 0.05). A significant decrease was observed in alpha-diversity in rectal swabs containing BPAs versus meconiums (p = 0.00408), whereas an increased variance was observed in beta-diversity in all samples (p < 0.05). As a result of a LEfSe analysis, Pseudomonadota was found to have a higher relative abundance in rectal swabs, and Bacillota was significantly higher in the meconiums of the twins. Conclusions: Our study strongly verified the relationship between the administration of antibiotics, dysbiosis, and colonization of BPAs in the infants’ gut microbiota. Further research would be beneficial and needed, comprising the natural development process of the infants’ gut microbiota.

Background: Colistin and carbapenem-resistant Klebsiella pneumoniae (Col-CRKP) represent a significant and constantly growing threat to global public health. We report here an outbreak of Col-CRKP infections during the fifth wave of COVID-19 pandemic. Methods: The outbreak occurred in an intensive care unit with 22 beds at a teaching university hospital, Isfahan, Iran. We collected eight Col-CRKP strains from seven patients and characterized these strains for their antimicrobial susceptibility, determination of hypermucoviscous phenotype, capsular serotyping, molecular detection of virulence and resistance genes. Clonal relatedness of the isolates was performed using MLST. Results: The COVID-19 patients were aged 24–75 years with at least 50% pulmonary involvement and were admitted to the intensive care unit. They all had superinfection caused by Col-CRKP, and poor responses to antibiotic treatment and died. With the exception of one isolate that belonged to the ST11, all seven representative Col-CRKP strains belonged to the ST16. Of these eight isolates, one ST16 isolate carried the iucA and ybtS genes was identified as serotype K20 hypervirulent Col-CRKP. The blaSHV and blaNDM-1 genes were the most prevalent resistance genes, followed by blaOXA-48 and blaCTX-M-15 and blaTEM genes. Mobilized colistin-resistance genes were not detected in the isolates. Conclusions: The continual emergence of ST16 Col-CRKP strains is a major threat to public health worldwide due to multidrug-resistant and highly transmissible characteristics. It seems that the potential dissemination of these clones highlights the importance of appropriate monitoring and strict infection control measures to prevent the spread of resistant bacteria in hospitals. [ABSTRACT FROM AUTHOR]