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The increase in multidrug-resistant bacteria has reached an alarming rate globally, making it necessary to understand the underlying mechanisms mediating resistance in order to discover new therapeutics. Tigecycline (TGC) is a last-resort antimicrobial agent for the treatment of serious infections caused by extensively drug-resistant Enterobacteriaceae.The TGC-resistant Escherichia coli mutants were obtained by exposing three different TGC-susceptible isolates belonging to ST131 (n = 2) and ST405 (n = 1) to increasing concentrations of TGC. The genetic alterations associated with reduced susceptibility to TGC were identified using whole genome sequencing. The fitness cost of TGC resistance acquisition, as well as incidence of cross-resistance, was also investigated.The TGC minimum inhibitory concentrations (MICs) of in vitro selected mutants were elevated 8 to 32 times compared with ancestral strains. Inactivating mutations (frameshift and nonsense) or amino acid substitutions were identified in genes encoding proteins with diverse functions, including AcrAB efflux pump or its regulators (lon and marR), Lipopolysaccharides (LPS) inner core biosynthesis enzymes (waaQ and eptB), ribosomal S9 protein (rpsI), and RNA polymerase β subunit. In most cases (but not all), acquisition of TGC resistance was associated with a fitness cost. While TGC resistance development was associated with cross-resistance to other members of the tetracycline family and chloramphenicol, hypersensitivity to nitrofurantoin was identified among heptose III-less LPS mutants.TGC resistance among the studied mutants was found to be multifactorial with extrusion by efflux transports being the most common mechanism. The LPS inner core biosynthesis pathway, as well as ribosomal S9 protein, could be additional targets for TGC resistance.

Background Patients with invasive infections caused by methicillin-resistant Staphylococcus aureus (MRSA), especially those with an elevated minimal inhibitory concentration (MIC) of vancomycin (VA), are likely to have treatment failure and poor outcomes. The aim of this study was to delineate and correlate the genotypes and phenotypes of clinical VA-intermediate S. aureus (VISA) from invasive infections in Taiwan. Methods Between 2006 and 2010, a total of 670 non-duplicate MRSA isolates were collected from patients with invasive infections, mostly from blood, as part of a nationwide antimicrobial surveillance program named Tigecycline in vitro Surveillance in Taiwan. Among them, 10 (1.5%) VISA (VA MIC = 4 mg/L) isolates were identified. Molecular typing with staphylococcal cassette chromosome mec (SCCmec), multilocus sequence typing, staphylococcal protein A (spa), mec-associated hypervariable region (dru), accessory gene regulator (agr), and pulse-field gel electrophoresis, and phenotypic analysis including antibiotic susceptibility testing, gene encoding Panton-Valentine leukocidin (pvl), and superantigenic toxin profiles, were analyzed. Results All but one isolate was defined as molecular health-care-associated MRSA: 6 as SCCmecIII-ST239-spa t037-agrI-dru7 (1 isolate) and dru14 (5 isolates), 2 as SCCmecII-ST5-spa t586-agrII-dru4, and one as SCCmecII-ST89-spa t3520-agrIII-dru7. One isolate was defined as SCCmecIV-ST59-spa t437-agrI-dru8, which was categorized as molecular community-associated MRSA. Five pulsotypes were identified; only one had a positive D-test and 3 were insusceptible to daptomycin (MIC ≧1 mg/L). Five isolates possessed sea-selk-selq, among them 4 belonged to SCCmecIII-ST239-spa t037-agrI. Conclusion In this study, VISA was rarely isolated from invasive MRSA infections, and most cases harbored limited genotypes and corresponding phenotypes.

This study aimed to investigate the in vitro activities of tigecycline (TGC) and the underlying molecular mechanisms of TGC stress response and resistance in clinical Enterococcus faecalis isolates from China.Antimicrobial susceptibility and antibiofilm activities of TGC in 399 E. faecalis isolates were evaluated. Heteroresistance was evaluated by population analysis profiling. Resistance and heteroresistance mechanisms were investigated by identifying genetic mutations in tetracycline (tet) target sites and through analysis of efflux protein inhibitors (EPIs). Furthermore, quantitative proteomics was used to investigate the global proteomic response of E. faecalis to TGC stress, as well as the resistance mechanisms of TGC within in vitro induced resistant isolate.TGC minimum inhibitory concentrations (MICs) against clinical E. faecalis isolates were ≤0.5 mg/L. TGC displayed remarkable inhibitory activity against biofilm formation. The occurrence rate of TGC heteroresistance was 1.75% (7/399), and the increased TGC MIC values of heteroresistance-derived clones could be reversed by EPI. TGC resistance was associated with mutations in the 16S rRNA site or 30S ribosomal protein S10. A total of 105 and 356 differentially expressed proteins was identified after being exposed to 1/2× MIC concentrations of TGC, while 356 differentially expressed proteins was identified in TGC-resistant isolate. The differentially expressed proteins were enriched in the translation and DNA replication process. In addition, multiple adenosine triphosphate (ATP)-binding cassette (ABC) transporters were upregulated.TGC exhibited excellent activity against a substantial proportion of clinical isolates from China. However, E. faecalis exhibited a strong adaptation mechanism during TGC exposure: mutation of TGC target sites and elevated expression of efflux pumps under TGC selection, resulting in TGC resistance.

We conducted this multicenter retrospective study to evaluate the prevalence, clinical patterns, and risk factors for tigecycline-induced liver injury, which is a type of drug-induced liver injury (DILI).Inpatients receiving intravenous tigecycline for ≥7 days were included. Patient information was collected to assess possible DILIs. The pattern and severity of tigecycline DILI were evaluated. A multivariable logistic regression model was used to identify the independent risk factors associated with tigecycline DILI.A total of 986 patients were identified and 397 patients were included in this study. The prevalence of tigecycline DILI was 10.3% (95% confidence interval [CI] = 7.51-13.7%). The most common type of tigecycline DILI was cholestatic, with mild severity observed in most cases. Abnormal baseline alanine aminotransferase levels (odds ratio [OR] = 3.11, 95% CI = 1.55-6.24, P = 0.001), intensive care unit admission (OR = 2.63, 95% CI = 1.32-5.36, P = 0.006), and treatment length (in weeks) (OR = 1.25, 95% CI = 1.05-1.49, P = 0.011) were independent risk factors for tigecycline DILI.Our results indicate that the prevalence of tigecycline DILI is high, and that the patients at risk should receive special attention.

We conducted a drug use investigation to investigate the safety and efficacy of tigecycline, which has been approved for clinical use for the treatment of multidrug-resistant gram-negative infections in Japan.This was an open-label, observational, multicenter cohort study that included all patients who received tigecycline.A total of 116 patients were registered between December 2012 and April 2016 and all of them were evaluated for safety and efficacy. Among them, 64 patients aged ≥65 years (55.2%) and five children aged15 years (4.3%) were included. Of these patients, 47 (40.5%) met the approved indications of tigecycline. Adverse drug reactions (ADRs) were observed in 41 patients (35.3%) with a total of 74 events. Serious ADRs were observed in 15 patients (12.93%) with a total of 33 events. There were 42 deaths, and 6 of these were considered to be caused by ADRs. Among the 116 patients, 65 achieved clinical response at the end of the observation period, and the efficacy rate was 73.9%. Furthermore, 46 patients were assessed as "cure" at the test of cure visit, and the cure rate was 59.0%. The eradication rate was 47.5% at the end of the observation period. Classified by pathogenic bacteria, the eradication rate of patients infected with the approved pathogens was 54.5%.Tigecycline was well-tolerated, and no additional safety concerns were noted. It was effective considering that most patients had poor physical conditions. The overall benefit-risk balance of tigecycline was favorable.

This study aimed to identify tigecycline-resistant tet(X4)-bearing Escherichia fergusonii isolated from pigs in China with a complete genome sequence.E. fergusonii was isolated by selective medium and screened from tigecycline-supplemented agar plates. The microbroth dilution method was used for antimicrobial susceptibility testing, and the minimal inhibitory concentration (MIC) results refer to the interpretation standard in the Clinical and Laboratory Standards Institute of America (CLSI). Whole-genome sequencing was performed on the Illumina HiSeq and Nanopore GridION platforms. The antimicrobial resistance (AMR) genes virulence genes and replicon types of plasmids were predicted by the CGE server.E. fergusonii EF21QZZ116 was identified from 760 faecal and caecal content samples and was resistant to tigecycline, tetracycline, ampicillin, sulfisoxazole, trimethoprim-sulfamethoxazole, spectinomycin, and florfenicol. The AMR genes tet(X4), blaTo the best of our knowledge, this is the first report of E. fergusonii carrying the tet(X4) gene isolated from a pig; this report provides insight into the AMR characteristics of E. fergusonii and offers insight into public health.

Background The emergence of concurrent levofloxacin- and trimethoprim/sulfamethoxazole (TMP/SMX)-resistant Stenotrophomonas maltophilia (LTSRSM) in Taiwan is becoming a serious problem, but clinical data analysis on this has not been reported. Methods A matched case-control-control study was conducted to investigate risk factors for LTSRSM occurrence in hospitalized patients. For patients with LTSRSM infection/colonization (the case group), two matched control groups were used: control group A with levofloxacin- and TMP/SMX-susceptible S. maltophilia (LTSSSM) and control group B without S. maltophilia. Besides, tigecycline, ceftazidime, cefepime, ciprofloxacin, gentamicin, amikacin, and colistin susceptibilities in collected LTSRSM and levofloxacin- and TMP/SMX-susceptible S. maltophilia (LTSSSM) isolates were compared. Results From January 2014 to June 2016, 129 LTSRSM from cultured 1213 S. maltophilia isolates (10.6%) were identified. A total of 107 LTSRSM infected patients paired with 107 LTSSSM-, and 107 non-S. maltophilia-infected ones were included. When compared with control group A, previous fluoroquinolone and TMP/SMX use was found to be independently associated with LTSRSM occurrence. When compared with control group B, mechanical ventilation, cerebrovascular disease, and previous fluoroquinolone use were risk factors for LTSRSM occurrence. Eighty-five LTSRSM and 85 LTSSSM isolates were compared for antibiotic susceptibilities; the resistance rates and minimum inhibitory concentrations of tigecycline and ceftazidime were significantly higher for LTSRSM than for LTSSSM isolates. Conclusion The emergence of LTSRSM showing cross resistance to tigecycline and ceftazidime would further limit current therapeutic options. Cautious fluoroquinolone and TMP/SMX use may be helpful to limit such high-level resistant strains of S. maltophilia occurrence.

Objectives Stenotrophomonas maltophilia MER1, a multidrug resistant (MDR) bacterium was isolated from the wastewater from a hospital, Shandong province, China. We attempted to reveal the genetic determinants related to its striking MDR features for effective treatment to S. maltophilia. Methods Antibiotic susceptibility testing of strain MER1 was performed by using the disk diffusion method on the Mueller-Hinton agar plates, and the minimum inhibitory concentrations (MICs) were determined according to the Clinical Laboratory Standard Institute protocols. The genome of MER1 was sequenced and assembled with a PacBio RS II and a BGISEQ-500 platform. Antibiotic resistance agents together with other transferability or adaptability determinants were identified by comparative genomics. Phylogenetic and contextual assays for these identified elements were conducted to assess the spread risk of MER1. Results Susceptibility testing reveals that strain MER1 is strikingly resistant to nine different antibiotics, including ampicillin, meropenem, amikacin, erythromycin, vancomycin, tetracycline, tigecycline, polymyxin E and ceftazidime. Several genes were identified to encode efflux pumps and inactivation agents accounting for MER1 resistance to above antibiotics, including meropenem, tigecycline and colistin regarded as the last-line therapy for infections caused by multidrug-resistant Gram-negative bacteria. MER1 co-harbors two non-mobile mcr homologs. A novel genomic region of variability was demonstrated to confer bacterial robustness and adaptability upon strain MER1. Conclusion Collective efforts revealed the multiple drug resistance properties and potential genetic determinants of S. maltophilia MER1 isolated from the hospital sewage. Comparative genomic analysis of S. maltophilia MER1 may provide insights into prevention and treatment of its antimicrobial resistance. Our findings would prompt public concern that the MDR genes in the reservoir of S. maltophilia may further spread into various ecological niches or medically high-risk pathogens.

Objectives The mobile tigecycline resistance gene tet(X4), conferring resistance to all tetracyclines, is largely reported from China, however the global spread of such a novel resistance mechanism is a concern for preserving the efficacy of these last-resort antibiotics. The aim of our study was to determine the genetic basis of resistance in a tigecycline-resistant Escherichia coli strain (2-326) isolated from sewage in Bergen, Norway, using whole-genome sequencing (WGS). Methods WGS was carried out using Illumina MiSeq-based sequencing. In vitro conjugation assays were performed to determine the potential of isolate 2-326 to transfer tigecycline resistance to other strains. Results Escherichia coli isolate 2-326 belongs to pathogenic sequence type 167 (ST167) and carries several clinically important antibiotic resistance genes including tet(X4), blaCTX-M-14, dfrA12, sul2, qnrS1 as well as several aminoglycoside resistance genes. Tigecycline resistance along with resistance to tetracycline, sulfamethoxazole, chloramphenicol and azithromycin was transferred to green fluorescent protein (GFP)-encoding E. coli strain CV601-GFP by conjugation. Conclusion To the best of our knowledge, this is the first report of E. coli carrying mobile tet(X4) gene from Norway. Our study demonstrates the ongoing spread of new mechanisms of resistance against last-resort antibiotics and the need for surveillance of such resistance factors in the population in order to mitigate their spread.

Objectives IMP-type carbapenemases are rarely detected in Europe and limited information is available to guide the treatment of infections caused by carbapenemase-producing Enterobacterales (CPE) producing these carbapenemases. Accurate antimicrobial susceptibility testing (AST) results are essential for optimal antibiotic management. Here we report discrepancies in AST of IMP-producing Enterobacterales (IMP-CPE) complicating the management of severe sepsis. Methods Antimicrobial susceptibilities were analysed by in-house VITEK® 2, Etest and broth microdilution (BMD). Carbapenemase-encoding genes were detected by PCR. Whole-genome sequencing (WGS) was performed using an Illumina MiSeq platform. Results Minimum inhibitory concentrations (MICs) determined by VITEK® 2 for Enterobacter hormaechei and Klebsiella oxytoca blood culture isolates were ≥16 mg/L for meropenem and ≤0.5 mg/L for ertapenem. In contrast, Etest analysis and BMD returned MICs of 2 mg/L and 1 mg/L, respectively. Both isolates tested positive for IMP carbapenemase-encoding genes by PCR. WGS revealed that both isolates carried the same blaIMP-4 gene. Based on VITEK® 2 susceptibilities, initial treatment was with tigecycline and amikacin. After subsequent deterioration, the patient was successfully treated with ertapenem and amikacin. Conclusion This case highlights that automated AST by VITEK® 2 can over-report meropenem resistance for IMP carbapenemase-producers compared with Etest and BMD. Clinicians need to be cautious deciding against carbapenem treatment based on VITEK® 2 susceptibility testing results for IMP-positive Enterobacterales. Tigecycline was inferior to carbapenem treatment for pyelonephritis caused by isolates expressing IMP carbapenemases, however specific evidence guiding the treatment of these infections is lacking.

Mycobacterial susceptibility testing is important for the management of nontuberculous mycobacteria (NTM) infections. The aim of the study is to determine the susceptibilities of tigecycline (TGC) and linezolid (LZD) against NTM. The study was carried out using stocks of NTM strains in the tuberculosis department of the microbiology laboratory. It was designed a retrospective study. LZD and TGC sensitivities of study isolates were analyzed by microdilution. Forty NTM isolates have been studied. LZD and TGC sensitivities varied according to the NTM type. It is concluded that each isolate should be individually evaluated due to variable susceptibilities to LZD and TGC.

Background Antimicrobial resistance (AMR) of non-fermenting Gram-negative bacteria (NFGNB) is increasingly recognized as urgent healthcare threat. Trend data on AMR of NFGNB in Saudi Arabia are either old or limited. The objective was to estimate the prevalence and resistance trends of isolated NFGNB in Saudi Arabia. Methods A retrospective multicenter study involving seven tertiary care hospitals in Saudi Arabia was conducted between 2011 and 2016. Susceptibility testing for non-duplicate isolates was performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines in College of American Pathologists accredited diagnostic microbiology laboratories in the participating hospitals. Results Out of 461,274 isolates, 100,132 (21.7%) were NFGNB which represented 30% of gram-negative pathogens. Pseudomonas aeruginosa was the most common (73.6%), followed by Acinetobacter baumannii (21.0%) and Stenotrophomonas maltophilia (5.3%). Resistance trends of P. aeruginosa were increasing for aztreonam (absolute increase during the study was 17.3%), imipenem (12.3%), and meropenem (11.6%). A. baumannii was fully resistant to several beta lactam drugs, and resistance trends were increasing for potential treatments such as tigecycline (25.1%) and tobramycin (15.5%). S. maltophilia was >90% resistant to trimethoprim/ sulfamethoxazole and ciprofloxacin by the end of the study. Conclusion We are reporting high and/or increasing resistance of NFGNB to common treatment options. The current findings call for urgent actions to combat the increasing resistance of NFGNB. Large scale sharing of AMR data collected at different hospitals with the Saudi AMR committee would be critical to set priorities and monitor progress.

Objectives: Tigecycline resistance mediated by the mobile tigecycline-inactivating enzyme gene tet(X) in Gram-negative bacteria is an emerging concern for global public health. However, limited information is available on the distribution of tet(X) in the natural environment. In this study, we investigated the presence of tet(X) in environmental Gram-negative bacteria. Methods: A carbapenem- and tigecycline-resistant Shewanella xiamenensis isolate (NUITM-VS1) was obtained from an urban drainage in Hanoi, Vietnam, in March 2021. Whole-genome sequencing analysis was performed by long- and short-read sequencing, resulting in a complete genome sequence. Antimicrobial resistance genes (ARGs) in the genome were detected based on the custom ARG database, including all known tigecycline resistance genes. Results: Shewanella xiamenensis isolate NUITM-VS1 harboured the tet(X4) gene and the blaOXA-48 carbapenemase gene on the chromosome. tet(X4) was flanked by IS91 family transposase genes, suggesting that the acquisition of tet(X4) was mediated by this mobile gene element (MGE), whereas no MGE was found surrounding blaOXA-48, consistent with previous findings that blaOXA-48-like β-lactamase genes are species-specific intrinsic ARGs in Shewanella spp. Conclusion: To the best of our knowledge, this is the first report of a tet(X4)-harbouring Shewanella sp. isolate. Our results provide genetic evidence of the complexity of the dynamics of clinically important ARGs among bacteria in the water environment.

Junta de Andalucía (CTS 164), Instituto de Salud Carlos III (Spain), Fondo Europeo de Desarrollo Regional (FEDER), European Union, through the research grants PI18/00826, P18-RT-4930, PI0206–2016, PIE16/00045 and PI19/01058, Spanish Ministry of Science and Innovation (MCIN/AEI/ 10.13039/501100011033/FEDER), RTI2018–101309-BC22, Chair “Doctors Galera-Requena in cancer stem cell research” (CMC-CTS963, Spanish Ministry of Science and Innovation (“Programa de Doctorado: Medicina Clínica y Salud Pública” B12.56.1)., Instituto de Salud Carlos III (FI17/00176), Junta de Andalucía (P18-RT-4930), University of Granada, CIBER-EHD is funded by the Instituto de Salud Carlos III

Objectives The aim of this study was to characterise a novel tet(X6)-carrying plasmid detected in a livestock-associated Acinetobacter towneri isolate. Methods PCR screening was performed to detect tet(X) variants in livestock-associated Acinetobacter spp. isolates. The tet(X6)-positive isolate was analysed by whole-genome sequencing. Functional cloning was performed to detect the activity of Tet(X6). Antibiotic susceptibility was determined by broth dilution and microbiological degradation assays. Site-directed mutagenesis was performed to identify the role of 23-Ala residue of Tet(X6) in tigecycline resistance. Results The tet(X6) gene was detected on a 159-kb plasmid (pAT205) carried by a tigecycline-susceptible A. towneri isolate recovered from a swine faecal sample. The genetic context of tet(X6) [ΔISVsa3–tet(X6)–abh–guaA–ISVsa3] is highly similar to that of the reported plasmid-borne tet(X) variants, suggesting that it may represent a common structure mediating the dissemination of plasmid-borne tet(X) genes. Additional resistance genes detected on pAT205 were carried by a Tn6205-like region and a disrupted class 2 integron. Gene expression and microbiological degradation assays consistently suggested that the activity of tet(X6) is weaker than that of tet(X3) and tet(X4). The 23-Ala residue of the first FAD-binding site conferred higher activity to Tet(X6) than the Gly reside conserved in the other plasmid-borne tet(X) variants, indicating that the site might be under selection. Conclusion This study alerts to the silent dissemination possibility of tigecycline resistance mediated by a novel plasmid. Continuous monitoring of plasmid-borne tet(X) is imperative for tackling its dissemination.

Summary Objectives Vancomycin-resistant E. faecium (VRE) is a common cause of healthcare-associated infections. The emergence of VRE with tigecycline resistance (TVRE) is increasing but its impact on patient outcome is still not well defined. This study aimed to assess risk factors for the acquisition of TVRE and of patient outcomes associated with TVRE carriage/infection. Methods At the University Hospital Frankfurt, we conducted a matched pair TVRE-VRE analysis to identify risk factors for TVRE carriage. Bed-to-bed contacts and potential transmission routes were reconstructed. TVRE were whole-genome sequenced to confirm suspected transmission events and to identify tigecycline resistance mechanisms. Results 76 TVRE cases were identified between 02/2014–04/2017 and compared to VRE colonized or infected controls. TVRE carriage was associated with exposure to tigecycline, an increased rate of bloodstream infections (BSI) with VRE or Candida spp., and higher mortality. Whole-genome sequencing-based analysis of 24 TVRE provided evidence for transmissions of TVRE, also across different wards. Conclusions Tigecycline exposure is the main risk factor for TVRE carriage. VRE/TVRE- and Candida-BSI are associated with worse clinical outcome. Hospital transmission of TVRE may occur despite strict contact precautions, whereas both antimicrobial stewardship and infection control interventions are of high importance to prevent emergence and spread of TVRE.

Background There is clinical and epidemiological evidence indicating that cigarette smoke exposure can significantly increase the usage of antibiotics by smokers to treat pulmonary infections, suggesting an increased risk of bacterial drug resistance. Pseudomonas aeruginosa is commonly found in infectious diseases closely related to cigarette smoke exposure and frequently acquires drug resistance. Recently, a study has demonstrated that cigarette smoke extract may induce Pseudomonas aeruginosa antibiotic resistance but the mechanism remain unknown. Objectives To explore the effect of cigarette smoke exposure on drug resistance in P. aeruginosa and the underlying mechanism using an in vitro model of cigarette smoke extract (CSE) exposure. Methods P. aeruginosa strains PAO1, PA103 and ATCC27853 were used in this study. Changes in drug resistance in P. aeruginosa after CSE exposure were evaluated by antimicrobial susceptibility tests. Additionally, differentially expressed genes related to drug resistance were detected by transcriptome sequencing and qRT-PCR. Results CSE increased both the MIC and MBC of levofloxacin and imipenem (MIC was not changed in ATCC 27853) against P. aeruginosa. However, CSE could only increase the minimum inhibitory concentration of tigecycline and minocycline against P. aeruginosa. Transcriptome sequencing and qRT-PCR indicated that MvaT and OprD levels decreased and MexEF-OprN levels increased. Conclusions Overall, our results showed that CSE may induce antibiotic resistance in P. aeruginosa. The results of antimicrobial susceptibility tests, transcriptome sequencing and qRT-PCR showed that CSE induced P. aeruginosa to the nfxC drug-resistant phenotype.

Tetracyclines continue to be important antimicrobials in veterinary medicine. However, the pharmacokinetics (PK) of tigecycline (TIG) and minocycline (MIN) in broiler chickens has not been investigated to date, and the PK of chlortetracycline (CTC) and tetracycline (TET) remains insufficiently researched, especially in terms of absorption. These antimicrobials have never been compared in a single setting in a single species; therefore, the aim of the present study was to compare the PK of TIG, MIN, CTC, and TET in broiler chickens. Each drug (10 mg/kg) was administered intravenously (IV) and orally (PO). The plasma concentrations of each drug were determined by liquid chromatography-tandem mass spectrometry, and the results were analyzed using compartmental and non-compartmental PK models. Despite the fact that all of the studied antimicrobials were administered at an identical IV dose, the area under the concentration–time curve between zero and the last sampling point (AUC0→t) for MIN (35,014 ± 3,274 μg × hour/mL) and CTC (41,851 ± 10,965 μg × hour/mL) differed significantly from that determined for TIG (18,866 ± 4,326 μg × hour/mL) and TET (17,817 ± 4,469 μg × hour/mL). After IV administration, the values of AUC0→t were also directly related to total body clearance values which were significantly higher for TIG (0.56 ± 0.14 L/hour × kg) and TET (0.60 ± 0.14 L/hour × kg) than for CTC (0.25 ± 0.05 L/hour × kg) and MIN (0.29 ± 0.03 L/hour × kg). In turn, after PO administration, TIG was absorbed in only 1.55% ± 0.82, and CTC in 30.54% ± 6.99, whereas the bioavailability of MIN and TET was relatively high at 52.33% ± 3.92 and 56.45% ± 9.71, respectively. The differences in PK parameters between these drugs, despite their structural similarities, suggest that active transport mechanisms may play a role in their absorption and distribution.

Acquisition of Hospital-acquired infections (HAIs) in intensive care units (ICUs) predispose patients to higher mortality rates and additional adverse events. Serbian adult ICUs are rarely investigated for HAIs. The aim of this study was to look into HAIs in an adult ICU and identify risk factors for acquisition of HAIs and mortality.This retrospective study included 355 patients hospitalized over a 2-year period. Patient characteristics, antimicrobial resistance patterns, and risk factors of acquisition and predictors of mortality in patients who had a HAI were examined.HAIs were diagnosed in 32.7% of patients. Resistance rates50% were observed in all antimicrobials except for tigecycline (14%), colistin (9%), and linezolid (0%). Predictors of HAI acquisition were underlying viral CNS infections and invasive devices-urinary and central venous catheters, and nasogastric tubes. Diabetes mellitus and intubation (odds ratio 2.5 and 6.7, P = .042 and.001) were identified as predictors for increased mortality in patients who had a HAI.Prevalence of HAIs and resistance rates are high compared to ICUs in other European countries. Risk factors for both acquisition of HAI and mortality were identified. Large-scale studies are necessary to look at HAIs in adult ICUs in Serbia.

Both pathogenic as well as nonpathogenic species of staphylococci have been reported in poultry, but these studies have not compared staphylococcal flora of both farmed and household broiler chickens. Staphylococci from farmed (n = 51) and household chicken intestines (n = 43) were isolated and tested for resistance to antimicrobials, presence of resistance genes, and inhibitory activity against other bacteria; correlation of resistance phenotype and genotype was also evaluated. At least 12 staphylococcal species were identified; Staphylococcus carnosus subspecies carnosus was the predominant species from both sources. Most farmed chicken staphylococci were resistant to tigecycline (38/51; 74.8%) while the highest level of resistance among the household chicken staphylococci was to clindamycin (31/43; 72.1%). The mecA gene was only detected in staphylococci from household chickens, whereas ermC and tetK or tetM were found in staphylococci from both groups of birds. Multidrug resistance (resistance ≥ 2 antimicrobial classes) was observed in 88% of resistant staphylococci ranging from 2 to 8 classes and up to 10 antimicrobials. Isolates produced inhibitory activity against 7 clinical bacterial strains primarily Enterococcus faecalis (25/88; 28.4%) and Escherichia coli (22/88; 25%). This study demonstrated that the staphylococcal population among farmed and household chickens varies by species and resistance to antimicrobials. These results may reflect the influence of the environment or habitat of each bird type on the intestinal microflora. As resistance in the staphylococci to antimicrobials used to treat human infections was detected, further study is warranted to determine strategies to prevent transfer of these resistant populations to humans via contamination of the poultry meat.

Objectives As a common nosocomial infection bacterium, A. baumannii’s drug resistance rate continues to rise. In this study, the objective was to explore the possible reasons for the increased drug resistance of A. baumannii after tigecycline treatment. Methods Based on the drug resistance analysis of 183 clinical isolates of A. baumannii, a pair of strains (AB711 and AB721) which changed their resistance after treatment was selected. Tigecycline was used to induce the drug resistance of strain AB711 in vitro. The differential expressed genes from A. baumannii strains were analyzed using whole gene sequencing (WGS ) and RNA sequencing (RNA-seq) combined with online MLST, SNP tools and bioinformatics software, and verified by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Results AB721 became more resistant to tetracyclines than AB711 at the initial detection. However, after a period of time, the resistance of AB711 and AB721 became consistent. This phenomenon can also be repeated using AB711 in vitro. After induction, the AB711 with increased MIC value of tigecycline was named AB712. The results of WGS, MLST and SNP based Phylogenetic tree indicated that AB711, AB712, AB721 were co-origin and belong to ST2 (Pasteur) / ST1791 (Oxford). Comparative transcriptome indicated that the Differential expression of some genes can play an important role in the resistance enhancement process of AB711. For example, compared with AB711, genes related to benzene-containing compound metabolic process, translation, ribosomal structure and biogenesis and so on were upregulated significantly in AB712. In addition, efflux pumps such as RND transporter permease subunit, EmrAB, MacB, and Tet resistance operon were also upregulated. Conclusion Tigcycline induced changes in the expression of some related genes in A. baumannii, which may be the main reason for its increased drug resistance.

Background Hypersensitivity reactions (HSRs) to tetracyclines and the related compound, tigecycline, can limit the use of these medications and compromise optimal patient care. Despite this, there is little discussion in the literature describing the presentation of these reactions or guiding clinicians on the management of these reactions in adult and pediatric patients. Objective To describe the clinical features, optimal diagnostic approach, and management of HSRs to tetracyclines. Methods Patients with reactions to tetracyclines at our institution from 2011 to 2019 were identified by retrospective chart review. Skin testing protocols were designed for each antibiotic. Graded challenge and desensitization procedures were devised based on medical history, skin testing results when available, and need for readministration. Results The HSRs to tetracyclines, their workup, and management are described for 10 patients, aged 7 to 68 years. Our skin testing protocols for doxycycline, minocycline, and tigecycline described herein had good negative predictive value. When skin testing was negative and the initial reaction was not severe, graded challenge to the culprit drug was performed. Using the included procedures, 3 patients were desensitized to oral doxycycline, 3 to oral minocycline, and 2 to intravenous tigecycline. All the desensitizations were successful. Conclusion Once identified, HSRs to tetracyclines can be further evaluated with skin testing and graded challenge and managed in appropriate cases with desensitization. These procedures can facilitate first-line therapy for patients who require tetracyclines but developed hypersensitivity reactions.

Objectives Treatment of infections caused by carbapenemase-producing Klebsiella pneumoniae (CPKP) frequently involves combination therapy with various antimicrobial agents in the hope of achieving synergistic effects. Routine laboratory antimicrobial synergy testing is a service that is currently unavailable owing to the laborious nature of the reference time–kill assay (TKA) as well as the widely used chequerboard method. In this study, we explored whether easier methods, based on the Etest technique, might offer a suitable alternative. Methods In vitro interactions of tigecycline combination with colistin, gentamicin, fosfomycin or meropenem against 26 CPKP isolates were evaluated employing the TKA, chequerboard method and three Etest methodologies (the MIC/MIC ratio, the cross formation and the agar/Etest method). Rates of consequent synergy and concordance of the studied methods were determined. Results All antimicrobial combinations demonstrated some degree of synergy against the CPKP isolates tested. No antagonism was observed for any of the combinations. All methods showed poor synergy concordance with the TKA, producing non-significant kappa (κ) results. Etest methods (MIC/MIC ratio and agar/Etest) exhibited fair agreement (κ = 0.29 and 0.38, respectively) with the chequerboard method. Conclusion There is a poor correlation between synergy testing methods of tigecycline combinations, which may be associated with their different endpoints. To elucidate method comparability and reliability, their correlation with clinical outcomes appears important.

With the increase of antibiotic resistance currently available at an alarming rate, new improved films of Chitosan (CS) have been achieved with different levels of Tigecycline (TIGE) using traditional casting technology. The structural, optical, and morphological characterizations of the prepared (CS/TIGE) composites were investigated using XRD, FT-IR, UV–visible, and FE-SEM. Also, the antibacterial characterization was investigated. XRD pattern shows a semi-crystalline peak at 2θ = 21° begins to appear at Cs/TIGE2 concentration and its intensity increase with increasing TIGE concentration which indicate the interaction between TIGE and Cs. FT-IR reveals conservation of the distinctive bands with change in both intensity and position that attributed to increase the ratios of TIGE in Chitosan. UV–vis spectra confirmed the interaction of the CS and the drug TIGE. FE-SEM photos confirm the increasing of TIGE particles on the surface of CS/TIGE films by increasing the ratios of TIGE. The antimicrobial effect of Chitosan and five different ratios of Chitosan with TIGE have been identified against four different bacterial species, two gram-negative (Escherichia coli, Bacillus subtilis) and two gram-positive bacteria (Staphylococcus aureus, Pseudomonas aeruginosa). The obtained results indicated that the composite Cs/TIGE can be used in many antimicrobial applications because of its greatly antimicrobial activity.

Summary Background Levofloxacin has been considered as an alternative treatment for Stenotrophomonas maltophilia infection. However, levofloxacin-resistant S. maltophilia (LRSM) are emerging worldwide. Aim To investigate LRSM risk factors in hospitalized patients and to determine antibiotic susceptibility patterns of LRSM isolates. Methods In a retrospective matched case–control–control study, LRSM patients (the case group) were compared with two control groups: levofloxacin-susceptible S. maltophilia (LSSM) patients (control group A) and non-S. maltophilia-infected patients (control group B). Conditional logistic regression was used to analyse risk factors for LRSM occurrence. Tigecycline, ceftazidime, colistin, and trimethoprim/sulfamethoxazole (TMP/SMX) susceptibilities in collected LRSM clinical isolates were determined. Findings A total of 105 LRSM, 105 LSSM, and 105 non-S. maltophilia-infected patients were analysed. The first multivariate analysis (cases vs group A) revealed that previous fluoroquinolones use was significantly associated with LRSM occurrence, and the second multivariate analysis (cases vs group B) revealed that previous fluoroquinolone use, previous intensive care unit stay, and the number of previous exposures to different classes of antibiotics were significantly associated with LRSM occurrence. Of all the LRSM isolates tested for antibiotic susceptibility, ceftazidime, TMP/SMX, tigecycline, and colistin resistance rates were 42.0, 99.0, 78.0, and 40.0%, respectively. Conclusion LRSM antibiotic susceptibility patterns revealed multiple-drug resistance, which further limits treatment options for clinicians. To reduce LRSM occurrence, proper use of antibiotics, especially fluoroquinolones, is mandatory.

Background A Klebsiella pneumoniae infection is a life-threatening disease among abdominal solid organ transplant (ASOT) recipients. The objectives of our present work are to investigate the distribution and drug resistance of pathogens, and clinical manifestation among ASOT recipients suffering from K pneumoniae infections. Methods The medical records of 53 ASOT recipients with 63 episodes of K pneumoniae infections from October 1, 2013 to June 1, 2019 were reviewed according to the Declaration of Helsinki and the Declaration of Istanbul. There were no grafts from prisoners used in these 53 patients and the donors were not coerced or paid. The distribution and drug resistance of each pathogen and clinical manifestation among ASOT recipients with K pneumoniae infections were retrospectively reviewed and summarized. Results Prevalence and mortality of K pneumoniae infections among ASOT recipients were 4.5% and 32.1%, respectively. The origins of K pneumoniae infections were the blood (n = 21), deep wound and skin (n = 10), urinary tract (n = 9), abdomen (n = 6), and lung (n = 7). The numbers of organs from donors after cardiac death and living-related donors were 52 and 1, respectively. Twenty-nine patients had a serum creatinine level >1.5 mg/dL at the onset of K pneumoniae infections. Fifty-eight percent of K pneumoniae strains were carbapenem resistant. The resistance rate of K pneumoniae to 5 of 12 antibiotics investigated was more than 60%. The strains were relatively susceptible to meropenem, tigecycline, sulfamethoxazole, and amikacin; while there were distinctly increasing trends of resistance to meropenem and amikacin as time went on. Conclusions The clinical manifestation of K pneumoniae infections included elevated serum creatinine level, high carbapenem-resistant rate, and mortality. The drug-resistance rates of K pneumoniae to the most commonly used antibiotics were high with an increasing trend of resistance in recent years. Tigecycline, meropenem, sulfamethoxazole, and amikacin are recommended to treat K pneumoniae infections among ASOT recipients.

Background OXA-48 is an Ambler class D β-lactamase that hydrolyses penicillin and imipenem but has poor hydrolytic activity against cephalosporins. However, very few clinical experiences of treating extended-spectrum β-lactamase (ESBL)-negative OXA-48 producers with cephalosporins have been published. Objectives The aim of this study was to report clinical experience of infections due to ESBL-negative OXA-48-producing Klebsiella pneumoniae (K. pneumoniae) treated with cephalosporins. Patients and methods A retrospective study was conducted at Vall d’Hebron University Hospital, in Barcelona (Spain). It reviewed all microbiological isolates of OXA-48-producers that did not co-produce ESBL from May 2014 to May 2017, and included only clinical strains of patients treated with a cephalosporin for ≥72 h. Results From the 75 isolations of OXA-48 producers, there were 17 isolations of ESBL-negative OXA-48-producing K. pneumoniae. Three patients were treated with cephalosporins with successful outcomes: a pneumonia in a neutropenic patient treated with cefepime and amikacin; an acute focal nephritis of a renal graft treated with ceftriaxone; and an intrabdominal post-surgical infection treated with cefepime in combination with tigecycline at the beginning, and ciprofloxacin afterwards. Conclusions Cephalosporins could be an alternative treatment in selected patients with ESBL-negative OXA-48-producing K. pneumoniae infections, especially to avoid carbapenem use. However, it remains unknown if they should be given in combination.

Objectives To develop an effective enrichment method for tet(X) detection, we performed PCR and Sanger sequencing to screen and confirm the presence of tet(X) gene. Methods Species were identified by MALDI-TOF MS analysis. The minimum inhibitory concentrations (MICs) of common antibiotics were determined by broth microdilution and interpreted according to the CLSI guidelines and EUCAST breakpoints. Results We obtained 29 (2.26%, 29/1284) tet(X4)-positive Escherichia coli, and 96.6% of those (28 isolates) exhibited resistance to tigecycline. Conclusion This specific screening strategy for functional tet(X) mediating tigecycline resistance will be useful to facilitate development and advancement of our knowledge of tet(X).

Introduction Multidrug resistance among bacteria increases the need for new therapeutic options. Tigecycline is one candidate drug, due to property of a wider anti-bacterial spectrum to multi-drug resistant (MDR) pathogens. However, it has still not been approved for use in pediatric patients. Methods In this study the effectiveness and safety of tigecycline in children was assessed retrospectively. Results A total of 36 pediatric patients, received tigecycline therapy with a median of 13 days (2–32 days). Tigecycline was used as a combination therapy in all cases. Microbiological eradication was achieved in 27 patients (75%) and clinical response was observed in 30 patients (83%). There were six cases (17%) of relapse. Conclusion Our findings suggest that tigecycline may be an option for children with severe infections due to multidrug resistant bacteria.

The emergence of plasmid-mediated tigecycline-resistant genes [tet(X3)to tet(X6)] in animals and humans has raised serious concerns over their possible cross-environmental dissemination. However, behavior of these emerging mobile tet(X)-variant genes in manure treatment processes, particularly for different composting treatments, has not yet been studied. Here, we explored the environmental behavior of mobile tet(X)-variant genes in two typical manure composting treatments and amended soils based on a large-scale molecular investigation across eight provinces in China. Results showed that tet(X4) was the predominant mobile tet(X)-variant gene in fresh manure, natural and thermophilic composting products with both the highest detection frequency (82.5% ± 14.7%), and absolute abundance of tet(X4)[4.26 ± 0.09) × 10

Previous work has shown increased expression of genes related to oxidative stress in nonlesional atopic dermatitis (ADNL) skin. Although mitochondria are key regulators of ROS production, their function in AD has never been investigated. Energy metabolism and the oxidative stress response were studied in keratinocytes (KCs) from patients with ADNL or healthy controls. Moreover, ADNL human epidermal equivalents were treated with tigecycline or MitoQ. We found that pyruvate and glucose were used as energy substrates by ADNL KCs. Increased mitochondrial oxidation of (very) long-chain fatty acids, associated with enhanced complexes I and II activities, was observed in ADNL KCs. Metabolomic analysis revealed increased tricarboxylic acid cycle turnover. Increased aerobic metabolism generated oxidative stress in ADNL KCs. ADNL human epidermal equivalents displayed increased mitochondrial function and an enhanced oxidative stress response compared with controls. Treatment of ADNL human epidermal equivalents with tigecycline or MitoQ largely corrected the AD profile, including high p-65 NF-κB, abnormal lamellar bodies, and cellular damage. Furthermore, we found that glycolysis supports but does not supersede mitochondrial metabolism in ADNL KCs. Thus, aerobic metabolism predominates in ADNL but leads to oxidative stress. Therefore, mitochondria could be a reservoir of potential therapeutic targets in atopic dermatitis.

Antimicrobial resistance has been recognized as an important emerging environmental pollutant. 'Last-resort' antibiotics including tigecycline, polymyxin E, daptomycin, vancomycin and linezolid are the 'last line of defence' for antibiotic resistant pathogen infections. Therefore, the presence of 'last-resort' antibiotic resistant pathogens in hospital environments and the nosocomial transmission of 'last-resort' antibiotic resistance poses a grave threat to the well-being of patients. In this work, the extent of resistance to 'last-resort' antibiotics in culturable pathogens in hospital wastewater was investigated. Resistance to 'last-resort' antibiotics were quantified for 1384 culturable Enterobacteriaceae, Enterococcus, Staphylococcus, and Pseudomonas strains. With these investigations, several significant findings were made: (1) a very high level of resistance to 'last-resort' antibiotics was found; (2) multiple resistance to antibiotics, including 'last-resort' antibiotics, was prevalent; (3) a high level of 'last-resort' antibiotic resistance phenotype-genotype inconsistency was found, suggesting knowledge gap for resistance mechanisms; 4) tet(X4)-containing tigecycline-resistant Gram-positive pathogens were found for the first time; 5) wastewater treatment processes are effective in preventing the release of 'last-resort' antibiotic resistant pathogens to the environment. This investigation reveals the severe situation on 'last-resort' resistance in the hospital environment, and implies high risk for nosocomial transmission of 'last-resort' antibiotic resistant pathogens.

The emergence of mobile Tigecycline-resistant tet(X3) and tet(X4) is believed to be a global threat to public health. Here, we investigated the prevalence of tet(X3) and tet(X4) in our metagenomic data of migratory birds. While tet(X4) was not identified in our samples, tet(X3) was found in two gut microbiomes of bird fecal samples, with 100% amino acid identity of sites 150–387. These results suggest that tet(X3) has been spreading into the environment for a long period of time and that there is an urgent need to control its further transmission.

Objectives The resistance rate of Klebsiella pneumoniae to commonly used antibiotics has been increasing rapidly, causing serious concern among clinicians and microbiologists. Resistance to carbapenems in K. pneumoniae is increasing dramatically in Chinese hospitals. Here we report the genome sequence of an NDM-1 and KPC-2 co-producing K. pneumoniae (CRKP380) isolated from a bloodstream infection in Hangzhou, China. Methods The whole genome sequence of strain CRKP380 was determined using an Illumina NovaSeq 6000 platform. Antimicrobial resistance genes (ARGs) were identified using the BacWGSTdb server. The phylogenetic relationship between strain CRKP380 and other K. pneumoniae strains isolated from Hangzhou currently deposited in the NCBI GenBank database was analysed using a core genome-based single nucleotide polymorphism strategy. Results Klebsiella pneumoniae CRKP380 was resistant to all antibiotics tested except tigecycline and colistin. The genome sequence of K. pneumoniae CRKP380 consisted of 75 contigs comprising 5 590 460 bp. According to the Pasteur multilocus sequence typing (MLST) scheme, CRKP380 belongs to ST11. Eight ARGs were identified in CRKP380, including two carbapenemase genes (blaKPC-2 and blaNDM-1). Ten phylogenetically-related K. pneumoniae strains from Hangzhou were identified with identical ARGs and the same capsular serotype KL105, but none of these strains carried the blaNDM gene. Conclusion Here we report the genome sequence of a K. pneumoniae ST11 clinical strain co-carrying blaNDM-1 and blaKPC-2 from Hangzhou, China. The genome sequence of CRKP380 can be used as a reference sequence for future comparative genomic analysis, including the acquisition and mobilisation of carbapenem resistance genes.

The poultry industry is among the main protein suppliers worldwide. Thus, this study determined the antibiotic resistance and virulence profiles of Enterococcus spp. along the farm-to-fork production chain of an intensive poultry system in the uMgungundlovu District, Kwazulu-Natal, South Africa. Overall, 162 samples along the continuum (growth phase, transport and post-slaughter) were evaluated for the presence of Enterococcus spp. using selective media, biochemical tests and polymerase chain reaction (PCR). Resistance profiles were assessed by Kirby-Bauer disk diffusion method following the WHO-AGISAR recommended antibiotics panel for Enterococcus spp. Antibiotic resistance and virulence genes were detected using real-time PCR. Clonal relatedness was evaluated by REP-PCR. Overall, 131 isolates were recovered across the continuum, (34% E. faecalis, 32% E. faecium, 2% E. gallinarum and 32% other Enterococcus spp.). Resistance to tetracycline (79%), erythromycin (70%), nitrofurantoin (18%), ampicillin (15%), streptomycin (15%), chloramphenicol (10%), ciprofloxacin (4%), tigecycline (4%), gentamicin (4%), teicoplanin (3%) was observed among all Enterococcus spp.; no vancomycin resistance (0%) was recorded. Also, 24% of E. faecium were resistant to quinupristin-dalfopristin. Twenty-four multidrug resistance (MDR) antibiograms were observed across all species; E. faecium (43%) showed the highest frequency of MDR. The most frequently observed antibiotic resistomes were tetM (76%) and ermB (66%) while smaller percentages were noted for aph(3')-IIIa (12%) and vanC1 (1%). Virulence genes efaAFs (100%), cpd (96%) and gelE (80%) were more prevalent in E. faecalis. Clonality revealed that isolates along the continuum were highly diverse with major REP-types consisting of isolates from the same sampling point. This study highlights the diversity of MDR Enterococcus in the food chain with isolates harbouring resistance and virulence genes. These could be reservoirs for the potential transfer of pathogenic enterococci carrying these genes from poultry to humans through the food chain continuum, thus, underscoring the need for routine antibiotic resistance surveillance in food animals.

Introduction: The presence of Acinetobacter baumannii outside hospitals remains unclear. This study aimed to determine the prevalence of multidrug-resistance (MDR) A. baumannii in the extra-hospital environment in Mthatha, South Africa and to investigate the frequency of carbapenemase-encoding genes. Material and Methods: From August 2016 to July 2017 a total of 598 abattoir samples and 689 aquatic samples were collected and analyzed presumptively by cultural methods for the presence of A. baumannii using CHROMagar™ Acinetobacter medium. Species identification was performed by autoSCAN-4 (Dade Behring Inc., IL) and confirmed by the detection of their intrinsic blaOXA-51 gene. Confirmed MDR A. baumannii isolates were screened for the presence of carbapenemase-encoding genes, ISAba1 insertion sequence and integrase intI1. Results: In total, 248 (19.3%) Acinetobacter species were isolated. Acinetobacter. baumannii was detected in 183 (73.8%) of which 85 (46.4%) and 98 (53.6%) were recovered from abattoir and aquatic respectively. MDR A. baumannii was detected in 56.5% (48/85) abattoir isolates and 53.1% (52/98) aquatic isolates. Isolates showed high resistance to antimicrobials most frequently used to treat Acinetobacter infections such as piperacillin/tazobactam; abattoir (98% of isolates resistant), aquatic (94% of isolates resistant), ceftazidime (84%, 83%), ciprofloxacin (71%, 70%), amikacin (41%, 42%), imipenem (75%, 73%), and meropenem (74%, 71%). All the isolates were susceptible to tigecycline and colistin. All the isolates carried blaOXA-51-like. The blaOXA-23 was detected in 32 (66.7%) abattoir isolates and 11 (21.2%) aquatic isolates. The blaOXA-58-like was positive in 7 (14.6%) and 4 (7.7%) abattoir and aquatic isolates, respectively. Both groups of isolates lacked blaOXA-24-like, blaIMP-type, blaVIM-type, blaNDM-1, blaSIM, blaAmpC, ISAba1 and inI1. Isolates showed high level of Multiple Antibiotic Resistance Index (MARI) ranging from 0.20-0.52. Conclusion: Extra-hospital sources such as abattoir and aquatic environments may be a vehicle of spread of MDR A. baumannii strains in the community and hospital settings. Keywords: Acinetobacter baumannii, Carbapenemase-encoding genes, Extra-hospital, Multidrug-resistance, ISAba1, intI1

Post-surgical intra-abdominal infections (IAIs) due to carbapenem-resistant Acinetobacter baumannii (CRAB) are difficult to treat due to suboptimal peritoneal penetrations of several antimicrobial agents. Tigecycline has favorable outcomes of treating IAIs due to multidrug-resistant organisms but occurrence of breakthrough bacteremia has been observed because this agent has low serum level. Colistin has in vitro activity against CRAB but data on treatment of IAIs is limited due to poor peritoneal penetration. The purpose of this retrospective study is to explore the outcomes of adjunctive intravenous (IV) colistin to IV tigecycline in the treatment of IAIs caused by CRAB. Of 28 patients with non-bacteremic post-surgical IAIs due to CRAB, 14 patients received IV tigecycline alone and 14 patients received IV tigecycline with IV colistin. The 14-day, 30-day, in-hospital mortality rates, the rate of breakthrough bacteremia and the rate of bacterial eradication were not significantly different. The adjunctive therapy of IV colistin was associated with significantly higher rates of renal complications (10/14) than those receiving IV tigecycline alone (3/14) (P value = 0.023). In addition, the patients receiving adjunctive IV colistin had significantly more unfavorable non-clinical outcomes including longer length of hospital stay (P value = 0.049) and higher antimicrobial cost (P value = 0.008) and non-antimicrobial costs (P value = 0.037). In this study, adjunctive IV colistin to conventional IV tigecycline in the treatment of non-bacteremic post-surgical IAIs caused by CRAB did not yield clinical benefit but caused higher renal complication and unfavorable non-clinical outcomes.

Aim Due to the current widespread bacterial resistance to many antibiotics − especially extended-spectrum β-lactams, carbapenems, and anti-pseudomonal drugs − therapy for severe pneumonia is very challenging. This study aimed to assess antimicrobial sensitivity patterns and optimisation of the antibiotic stewardship program applied at a university-affiliated paediatric intensive care unit (PICU). Subjects and methods This prospective cohort study included all patients aged 1 month to 12 years, admitted to the PICU with severe pneumonia episodes indicated for mechanical ventilation, and were followed up and investigated. Non-bronchoscopic bronchoalveolar lavage specimens were tested for positive microbiological yields and examined for their susceptibility pattern. Results Of 85 patients with 96 episodes, 69 of them yielded positive growth: 43 were community-acquired pneumonia episodes, 62.79% of which were of unidentified cause. The isolated bacteria were predominantly due to Chlamydia pneumonia (18.6%) followed by Staphylococcus aureus and its resistant form (9.3%). Hospital and ventilator-associated pneumonia were mainly related to Gram-negative bacteria (91.67% and 87.8%, respectively), especially Klebsiella acinetobacter and Pseudomonas. There was a significant increase in multi-drug resistance among Gram-negative bacteria, which was considered an independent risk factor of mortality (P = 0.003). Conclusion Severe community-acquired pneumonia was treated with macrolides in combination with vancomycin or linezolid if methicillin-resistant S. aureus was suspected. This was appropriate, in view of its causative agents and their susceptibility pattern. Hospital and ventilator-associated pneumonia caused by resistant Gram-negative organisms might have better outcomes by adding tigecycline or colistin in combination with fluoroquinolones. Owing to the widespread resistance of many Gram-negative bacteria, it is recommended that the antibiotic stewardship program be frequently updated.

Objectives This study focused on estimating the prevalence of extended-spectrum β-lactamases (ESBLs), plasmid-mediated AmpC β-lactamases, carbapenemases and MCR-1-producing Escherichia coli in canine faeces from a public park in Quito, Ecuador. Methods Phenotypic and genotypic characterisation of E. coli isolated from 50 canine faecal samples recovered from a city park in Quito was performed. In addition, a multiple choice survey was conducted among 50 dog owners. Results Of the 50 faecal samples, 20 (40.0%) presented E. coli resistant to ceftriaxone. Moreover, 23 E. coli isolates were recovered for further analysis. All of the isolates showed as multidrug-resistant (MDR) phenotype (resistant to three or more antibiotic families). Resistance to carbapenems, tigecycline and amikacin was not observed. No major clonal relatedness was observed among the resistant isolates. The ESBL genes blaCTX-M-15, blaCTX-M-55 and blaCTX-M-65 were the most common. Two isolates harboured the blaCMY-2 gene and one isolate harboured both mcr-1 and blaCTX-M-65. Statistical analysis showed that older people were more conscious of collecting and disposing of dog faeces than subjects aged Conclusion The finding of MDR E. coli in dog faeces in a city park in Ecuador illustrates the importance of analysing canine faeces in public settings (e.g. parks, playgrounds) as part of surveillance programmes for MDR E. coli. In addition, this research might be a sentinel sampling method to gain a better understanding of community sources of antibiotic-resistant Enterobacteriaceae at human–animal–environment interfaces.

Objectives Carbapenem-resistant Acinetobacter baumannii (CRAB) have emerged as a serious threat to public-health worldwide. This study aimed to determine the antimicrobial susceptibility of A. baumannii isolates in Iran and to investigate oxacillinase-encoding determinants and their association with insertion sequence ISAba1 in CRAB isolates. Methods This study was performed on A. baumannii isolates recovered from patients with burn wound infections during 2013. All isolates were evaluated for antimicrobial susceptibility by the disk diffusion method. Minimum inhibitory concentrations (MICs) of five antibiotics (imipenem, meropenem, polymyxin B, colistin and tigecycline) were determined for all CRAB isolates. PCR was performed to determine the distribution of blaOXA determinants and ISAba1 insertion upstream of each corresponding gene in the CRAB isolates. Results A total of 65 A. baumannii isolates were recovered during the 1-year period, with CRAB accounting for 63 (96.9%) of isolates. Polymyxin B, colistin and tigecycline were the most effective agents against CRAB isolates, with susceptibility rates of 100%, 87.3% and 65.1%, respectively. The proportion of CRAB isolates carrying oxacillinase determinants was as follow: blaOXA-51-like, 100%; blaOXA-23-like, 74.6%; blaOXA-24/40-like, 47.6%; and blaOXA-235-like, 12.7%. ISAba1, ISAba1–blaOXA-23-like and ISAba1–blaOXA-51-like were detected in 100%, 41.3% and 1.6% of CRAB isolates, respectively. Co-occurrence of blaOXA determinants or inserted ISAba1 upstream of the corresponding genes was associated with increased carbapenem MICs (≥128 μg/mL). Conclusion The emergence of high-level CRAB with blaOXA and ISAba1–blaOXA family in burn patients is a matter of increasing clinical concern, emphasising the need for infection control efforts to limit such problematic bacteria.

Objectives The aim of this study was to monitor the trends in antimicrobial resistance from the blood samples isolated from the Chinese mainland. Methods All clinical isolates were collected from 18 hospitals. The minimal inhibitory concentrations (MICs) were tested in a central laboratory using the agar dilution method recommended by the Clinical and Laboratory Standards Institute. The susceptibilities of isolates to antimicrobial agents were determined by using Clinical and Laboratory Standards Institute or European Committee on Antimicrobial Susceptibility Testing (EUCAST) 2017 guidelines. Results A total of 1758 strains of various types with the sum ≥ 30 were isolated from blood specimens in 2015–2016. The detection rates of extended-spectrum β-lactamases (ESBLs) among Escherichia coli were 55.6%, whereas those in Klebsiella pneumoniae were 22.4%. Carbapenems, moxalactam, tigecycline, and amikacin displayed desirable antibacterial activity against Enterobacteriaceae, but a significant increase in Klebsiella pneumoniae to carbapenems was noted. Nonfermenters were highly resistant to carbapenems, especially in Acinetobacter Baumannii isolates, >70％ of which were resistant. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) reached 36.1% and 90.4%, respectively. Staphylococcus aureus had 100% susceptibility to vancomycin. Enterococcus faecium isolates showed significantly higher resistant rates to most of the tested antimicrobial agents than Enterococcus faecalis isolates. While vancomycin-resistant Enterococcus (VRE) was 3.28%, the non-susceptible rate of linezolid to Enterococcus faecalis was 6.8%. Conclusions This study revealed the major bacterial pathogens’ antibiotic susceptibility patterns involved with bloodstream infection in mainland China.

a b s t r a c t The Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) commenced in 2004 to longitudinally monitor global changes in bacterial susceptibility to a suite of antimicrobial agents. The current study examined the activity of tigecycline and comparators against isolates collected across Eastern Europe between 2004 and 2010. Minimum inhibitory concentrations were determined using Clinical and Laboratory Standards Institute (CLSI) broth microdilution methodologies. Antimicrobial susceptibility was deter- mined using CLSI interpretive criteria, and tigecycline susceptibility was established using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints. This study included 10 295 Gram-negative and 4611 Gram-positive isolates from 42 centres. Extended-spectrum -lactamases (ESBLs) were reported among 15.3% of Escherichia coli and 39.3% of Klebsiella pneumoniae isolates; the highest rates were observed in Turkey (30.9%) and Bulgaria (53.8%), respectively. Imipenem-non- susceptible K. pneumoniae were identified only in Turkey. ESBL-positive E. coli were highly susceptible to imipenem (95.1%), meropenem (98.0%) and tigecycline (98.5%). Most antimicrobials showed poor activity against Acinetobacter baumannii and Pseudomonas aeruginosa. Vancomycin resistance was noted among 0.9% of Enterococcus faecalis and 11.7% of Enterococcus faecium isolates. High rates of susceptibility were reported for linezolid (99.7%) and tigecycline (100%) against E. faecium. One-quarter of Staphylococcus aureus isolates were meticillin-resistant S. aureus (MRSA), with the highest rate in Romania (51.5%); all MRSA were susceptible to linezolid, tigecycline and vancomycin. Antimicrobial resistance is high in much of Eastern Europe, with considerable variation seen among countries. Tigecycline and the carbapenems retain excellent activity against many pathogens from Eastern Europe; linezolid and vancomycin are active against most Gram-positive pathogens.

Objectives Carbapenem-resistant Acinetobacter baumannii (CRAB) has become a worldwide issue. This study aimed to characterise the epidemiology and genetic relationships of A. baumannii isolates in Guangdong Province, China. Methods CRAB isolates were collected from five municipal hospitals from June–December 2017. The 16S–23S rRNA intergenic spacer region was used for confirmation of strain identity. Antimicrobial susceptibility testing and the CarbAcineto NP test were performed to analyse the resistance spectrum and carbapenemase production of the isolates. PCR-based assays were used to detect β-lactamase genes and related mobile genetic elements. Genetic diversity among the isolates was analysed by enterobacterial repetitive intergenic consensus (ERIC)-PCR, multilocus sequence typing (MLST) and multiplex PCR. Results A total of 122 isolates were confirmed as A. baumannii; all were resistant to the tested antibiotics except for tigecycline and colistin. The CarbAcineto NP test showed that 93.4% of the isolates produced a carbapenemase. blaOXA-23-like and extended-spectrum β-lactamase-encoding genes were found by PCR in 94.3% and 91.8% of the isolates, respectively. Furthermore, the genetic environment of blaOXA-23-like was mainly associated with transposons Tn2008 (46.1%), Tn2006 (27.0%) and Tn2009 (20.9%). MLST identified six existing sequence types (STs) and three novel STs, of which ST195 (35.7%) and ST208 (32.1%) were the most common, belonging to clonal group 92 and European clone II. Conclusion This study suggests that co-production of β-lactamases was the major resistance mechanism of CRAB isolates. Dissemination of blaOXA-23-like may be facilitated by transposable elements. ST195 and ST208 were the predominant epidemic types of A. baumannii in Guangdong Province.

Here, we evaluated the combinations of antibiotics polymyxin B (PMB), tigecycline (TGC) and meropenem (MEM) by time-kill curves (TKC) against carbapenem-resistant Enterobacter cloacae isolates. Combination of PMB/TGC and PMB/MEM showed promising results in sub-inhibitory concentration of PMB indicating the possibility of reducing the dose of PMB used in the treatment.

Global emergence of Tigecycline resistant Acinetobacter baumannii (TRAB) is on the horizon and poses a very serious threat to human health. There is a pressing demand for suitable therapeutics against this pathogen, particularly a vaccine to protect against TRAB infections. We present a comprehensive investigation of the complete proteome of a TRAB AB031 strain to predict promiscuous antigenic, non-allergenic, virulent B-cell derived T-cell epitopes and formulate a multi-epitope vaccine against the pathogen. We identified epitopes from three proteins: outer membrane protein assembly factor (BamA), fimbrial biogenesis outer membrane usher protein (FimD) and type IV secretion protein (Rhs) that are appropriate for vaccine design. These proteins constitute the core proteome of the pathogen, are essential, localized at the pathogen surface, non-homologous to humans, mice and to the beneficial probiotic bacteria that reside the human gut. Moreover, these proteins are ideal candidates for experimental investigation as they have favorable physicochemical properties and have strong cellular interacting networks. The predicted epitopes: FPLNDKPGD (BamA), FVHAEEAAA (FimD) and YVVAGTAAA (Rhs) have exo-membrane topology for efficient recognition of the host immune system and high affinity for the most prevalent allele in human populations, the DRB*0101. These epitopes were linked and attached to an adjuvant to enhance its antigenicity. The multi-epitope vaccine-construct was docked with the TLR4 receptor to assess its affinity for the protein and thus its presentation to the host immune system. Docking results were validated through molecular dynamics simulations and binding free energies were calculated using the molecular mechanics/generalized Born (MM-GBSA) method. In conclusion, we expect the designed chimeric vaccine is highly likely to be effective against infections caused by TRAB.