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Purpose: With the spread of multiple drug-resistant bacteria, blaNDM-1 and mcr-9 have been detected in various bacteria worldwide. However, the simultaneous detection of blaNDM-1 and mcr-9 in Enterobacter hormaechei has been rarely reported. This study identified an E. hormaechei strain carrying both blaNDM-1 and mcr-9. We investigated the genetic characteristics of these two resistance genes in detail, elucidating various potential mechanisms by which they may be transmitted. Methods: Bacterial genomic features and possible origins were assessed by whole-genome sequencing (WGS) with Illumina and PacBio platforms and phylogenetic analysis. Subsequent investigations were performed, including antimicrobial susceptibility testing and multilocus sequence typing (MLST). Results: We isolated an E. hormaechei strain DY1901 carrying both blaNDM-1 and mcr-9 from the sputum sample. Susceptibility testing showed that the isolate was multidrug-resistant. Multiple antibiotic resistance genes and virulence genes are widely distributed in DY1901. S1-PFGE, Southern blotting, and plasmid replicon typing showed that DY1901 carried four plasmids. The plasmid carrying mcr-9 was 259Kb in size and belonged to IncHI2, while the plasmid carrying blaNDM-1 was 45Kb in length and belonged to IncX3. Conclusion: The E. hormaechei strain isolated in this study has a broad antibiotic resistance spectrum, posing a challenge to clinical treatment. Plasmids carrying mcr-9 are fusion plasmids, and those taking NDM are widely disseminated in China, suggesting that we should conduct routine genomic surveillance on such plasmids to curb the spread of drug-resistant bacteria in the region. [ABSTRACT FROM AUTHOR]

Purpose: Nosocomial infections caused by New Delhi metallo-β-lactamase (NDM)-producing bacteria are prevalent worldwide. However, such diseases caused by NDM-producing Aeromonas caviae had never been reported. Our study aimed to elucidate the genomic characteristics of NDM-1-producing A. caviae isolated from hospital patients. Methods: Bacterial genomic features and possible origins were assessed by whole-genome sequencing (WGS) and phylogenetic analysis. Subsequent investigations include antimicrobial susceptibility testing and multilocus sequence typing (MLST). Results: We identified here two NDM-1-producing A. caviae isolates from bacteremia. Susceptibility testing showed that two isolates were multi-drug resistant and shared a similar resistance profile and were only sensitive to amikacin and trimethoprim/sulfamethoxazole. Both A. caviae isolates carry the carbapenem resistance gene blaNDM-1 and also have antibiotic resistance genes such as β-lactams, AmpC enzymes, macrolides, aminoglycosides, and quinolones. S1-PFGE and Southern blot analysis were negative. Whole-genome sequencing and comparative analysis revealed that these two isolates shared a close relationship. Conclusion: To the best of our knowledge, this work describes the first detection of non-plasmid encoded blaNDM-1 in A. caviae. The A. caviae isolated in this study has a broad drug resistance spectrum. Phenotypic and molecular analysis indicated the two isolates belong to the same clone. Routine genomic surveillance of this species is now necessary to effectively curb the further dissemination of carbapenem-resistant bacteria in the region. [ABSTRACT FROM AUTHOR]

Background: The emergence of the plasmid-borne colistin-resistant gene (mcr-1) poses a great threat to human health. What is worse, the recent observations of the coexistence of mcr-1 with carbapenemase encoding genes in some bacteria caused even more concern. Yet, there is a lack of observations of such strains in the human gut. Methods: The isolation of E. coli L889 was performed on selective medium plates. Antibiotic susceptibilities were determined by an agar dilution and a broth microdilution method. Multi-locus sequence typing (MLST) and acquired resistance genes were also characterized. Transferability of blaNDM-9/mcr-1-carrying plasmids was determined by conjugation, replicon typing and S1-Pulsed-field gel electrophoresis (S1-PFGE), and Southern blotting. The sequences of these plasmids were analyzed by using whole-genome sequencing with Illumina Novaseq and Nanopore platforms. Results: E. coli L889 was identified as ST1101 concomitantly carrying blaNDM-9 and mcr-1 from a stool sample. Antimicrobial susceptibility tests showed that it was resistant to various antimicrobial agents and only susceptible to tigecycline. Notably, blaNDM-9 was located on a ∼ 114-kb untypable plasmid, while mcr-1 was located on a ∼ 63-kb IncI2 plasmid. Conclusion: Our research, to our knowledge, first reported an ST1101 E. coli strain with an untypeable blaNDM-9-harbouring plasmid and an IncI2 mcr-1-carrying plasmid. The colonized E. coli strains potentially contribute to the dissemination and transfer of blaNDM-9 and mcr-1 to clinical isolates, which is a considerable threat to public health and should be closely monitored. [ABSTRACT FROM AUTHOR]

Purpose: To explore the epidemiological characteristics and risk factors of bloodstream infections (BSI) in patients who develop agranulocytosis fever after allogeneic hematopoietic stem cell transplantation (allo-HSCT). This study also provides a basis for the clinical treatment of BSI. Methods: A retrospective analysis of 397 allo-HSCT patients in the Department of Hematology of our hospital was conducted from January 2013 to December 2017 to analyze the incidence of BSI, the distribution and types of pathogenic bacteria, and drug resistance rates. We also determined whether various parameters are risk factors to BSI, including the patient age, gender, disease type, transplantation method, stem cell source, pre-treatment with anti-thymocyte globulin (ATG), and agranulocytosis time. Results: Among the 397 allo-HSCT patients, 294 had a fever during the period of agranulocytosis, and 52 cases were found to have BSI. The incidence of BSI in patients with agranulocytosis fever was 17.7% (52/294). Among the 60 pathogens detected, 43 (71.67%), 10 (16.67%), and 7 (11.67%) were Gram negative strains, Gram positive strains, and fungi, respectively. The most common bacteria were Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The detection rate of extended-spectrum β-lactamase (ESBL) was 40.0%, and carbapenem-resistant Enterobacteriaceae (CRE) accounted for 17.9%. Single-factor and multi-factor analyses showed that pre-treatment with ATG, agranulocytosis time (≥ 21 days), and stem cell source were risk factors for BSI. Conclusion: We found that in our hospital, BSIs in allo-HSCT patients are mainly caused by Gram-negative bacteria, and the resistance rate to carbapenem drugs is high. Pre-treatment with ATG, agranulocytosis time (≥ 21 days), and stem cell source are risk factors for BSI. [ABSTRACT FROM AUTHOR]

Background: Citrobacter freundii is the most common class of pathogens in the genus Citrobacter and is an important pathogen associated with certain underlying diseases or immune dysfunction. The aim of this study was to elucidate the resistance mechanism of clinically derived carbapenem-resistant C. freundii isolate and to characterize the genetic environment and delivery pattern of the IncN1 plasmid carrying the blaIMP-4 gene from C. freundii isolate. Materials and Methods: We identified a clinical isolate of C. freundii L91 carrying blaIMP-4 and performed phylogenetic analysis by whole-genome sequencing. The complete genomic sequence of L91 was obtained using the Illumina HiSeq 4000-PE150 and PacBio RS II platforms. Antimicrobial susceptibility testing was determined by the VITEK 2 system. Plasmid characteristics were presented by S1-pulsed-field gel electrophoresis (PFGE), Southern blotting and conjugation experiments. Results: S1-PFGE, Southern blot and conjugation assay confirmed the presence of blaIMP-4 genes on a conjugative plasmid in this isolate. C. freundii L91 and transconjugant L91-E. coli 600 strains both showed resistance to carbapenems. In silico analysis further showed that pIMP-4-L91 is an IncN1 plasmid with a length of 51,042 bp. Furthermore, blaIMP-4 gene was found encoded in the blaIMP-4-qacG2-aacA4-catB3 cassette array within a class 1 integron. A conserved structure sequence (ΔISKpn27-blaIMP-4-ΔISSen2-hp-hp-IS 6100) was found in the upstream and downstream of the blaIMP-4. Conclusion: We performed a comprehensive phylogenetic analysis of carbapenemase-resistant C. freundii and elucidated the resistance mechanism of clinically derived C. freundii L91. Not only that, we also found that the blaIMP-4 gene is located on the IncN1 plasmid and has a horizontal transfer function and a certain ability to spread. To lower the risk of the dissemination of such C. freundii isolates in clinical settings, more surveillance is needed in the future. [ABSTRACT FROM AUTHOR]

Purpose: Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae bacteria causes nosocomial infections worldwide. However, KPC-producing K. pneumoniae outbreak has never been reported in Shandong Province, China. The purpose of our study was to elucidate the epidemiological and drug resistance mechanisms of KPC-producing K. pneumoniae strains collected from a large teaching hospital in Shandong during the outbreak. Moreover, we attempted to characterize the genetic environment and phylogenetic analysis of blaKPC-2 in outbreak isolates. Methods: We monitored a 64-day outbreak of infection in a general hospital in Shandong Province, and the bacteria causing the infection were all ST11-type K. pneumoniae. The genotype correlation of KPC-producing K. pneumoniae isolates was assessed by whole-genome sequencing (WGS) phylogenetic analysis. Subsequent studies included antibiotic susceptibility testing, multilocus sequence typing (MLST) and S1-pulsed-field gel electrophoresis (S1-PFGE), Southern blot hybridization. Results: From February 1, 2018 to April 5, 2018, 14 KPC-producing K. pneumoniae isolates from different wards were collected. All 14 isolates were resistant to carbapenems and carried the extended-spectrum β-lactamase (ESBL) gene as well as fosA, and sul genes. Whole-genome analysis showed that all 14 the outbreak isolates were all ST11 type. The blaKPC-2 carrying plasmids were all belong to IncFIIK2 type, and the size ranged from 94 kb to 368 kb. Conclusion: As far as we know, this report first describes the genomics characterization of KPC-2-producing K. pneumoniae outbreak isolates from Shandong Province, China. In our study, these isolates appeared to be cloned, and ST11 K. pneumoniae was the major clone caused the outbreak. Therefore, routine surveillance of such strains in this region is urgently warranted. [ABSTRACT FROM AUTHOR]