Multiple Plasmid Vectors Mediate the Spread of fosA3 in Extended-Spectrum-β-Lactamase-Producing Enterobacterales Isolates from Retail Vegetables in China.

The plasmid-mediated fosfomycin resistance gene fosA3 has been detected in Enterobacterales from various sources but has rarely been reported in vegetables. In this study, the aim was to investigate the prevalence of and, subsequently, to characterize fosA3-positive Enterobacterales isolates from retail vegetables. Seventeen (7.3%) fosA3-carrying strains were identified from 233 extended-spectrum-β-lactamase-producing Enterobacterales isolates from vegetables. All 17 isolates, including six Escherichia coli, seven Klebsiella pneumoniae, two Raoultella ornithinolytica, and two Citrobacter freundii isolates, carried blaCTX-M S1-nuclease pulsed-field gel electrophoresis (S1-PFGE) and hybridization confirmed that the fosA3 genes in 16 isolates were located on plasmids ranging in size from ∼40 kb to ∼250 kb, except one located on chromosome of C. freundii All the fosA3-carrying plasmids from 16 fosA3-positive isolates were successfully transferred into the recipient bacteria by transformation or conjugation. In agreement with data determined with isolates from food animals, the IncHI2/ST3 and IncN-F33:A-:B-/F33:A-:B plasmids were the main vectors of fosA3 in E. coli Additionally, F24:A-:B1, IncFIIK-IncR, IncFIIS, IncR, and two untypeable plasmids were found for the first time to be vectors for fosA3 in Enterobacterales The genetic contexts of fosA3 in 15 Enterobacterales isolates differed due to insertion and/or loss of molecular modules mediated by mobile elements. However, all fosA3 genes were flanked by IS26, as commonly observed in other fosA3-carrying plasmids. Here, we report a high rate of detection of fosA3 genes, mediated by multiple plasmid vectors, in ESBL-producing Enterobacterales from retail vegetables. FosA3-producing Enterobacterales could be transmitted to the human body by direct contact or consumption of vegetables, which might pose a potential threat to public health.IMPORTANCE This report provides important information on the transmission and epidemiology of fosA3 among Enterobacterales isolates from vegetables. The rate of occurrence of fosA3 in ESBL-producing Enterobacterales from retail vegetables is high, and fosA3 was found to be carried by diverse plasmids. Some novel genetic contexts of fosA3 and novel fosA3-carrying plasmids, including several plasmid types common in K. pneumoniae, were identified, increasing the number of known transfer vectors for the fosA3 gene and reflecting the complexity of fosA3 transmission in Enterobacterales The capture of fosA3 by the resident plasmid of K. pneumoniae will accelerate the spread of fosA3 in K. pneumoniae, one of the most pathogenic species in clinical medicine. Considering the clinical importance of fosfomycin, and the fact that vegetables are directly consumed, the fosfomycin resistance genes present a risk of transmission to the human body through the food chain and thus pose a threat to public health.

Lv L ，Huang X ，Wang J ，Huang Y ，Gao X ，Liu Y ，Zhou Q ，Zhang Q ，Yang J ，Guo JY ，Liu JH ... -  《mSphere》

Prevalence of Plasmid-Mediated Fosfomycin Resistance Gene fosA3 Among CTX-M-Producing Escherichia coli Isolates from Chickens in China.

Jiang W ，Men S ，Kong L ，Ma S ，Yang Y ，Wang Y ，Yuan Q ，Cheng G ，Zou W ，Wang H ... -  《-》

Dissemination of the bla(NDM-5) Gene via IncX3-Type Plasmid among Enterobacteriaceae in Children.

The continuous emergence of novel New Delhi metallo-β-lactamase-5 (NDM-5)-producing Enterobacteriaceae isolates is receiving more and more public attention. Twenty-two NDM-5-producing strains were identified from 146 carbapenemase-producing Enterobacteriaceae (CRE) strains isolated from pediatric patients between January and March 2017, indicating that the blaNDM-5 gene has spread to children. All 22 isolates, including 16 Klebsiella pneumoniae strains, four Klebsiella aerogenes strains, and two Escherichia coli strains, showed significantly high resistance to β-lactam antibiotics (except aztreonam) but remained susceptible to tigecycline and colistin. K. pneumoniae and K. aerogenes strains were respectively defined as homologous clonal isolates by pulsed-field gel electrophoresis (PFGE). Multilocus sequence typing (MLST) results confirmed the genetic relatedness with all K. pneumoniae strains belonging to sequence type (ST) 48. Two E. coli isolates (ST617 and ST1236) were considered genetically unrelated. Twenty-two blaNDM-5 plasmids were positive for the IncX3 amplicon and showed almost identical profiles after digestion with HindIII and EcoRI. Four representative strains (K. pneumoniae K725, K. aerogenes CR33, E. coli Z214, and E. coli Z244) were selected for further study. Plasmids harboring blaNDM-5 showed strong stability in both clinical isolates and transconjugants, without apparent plasmid loss after 100 serial generations. S1-PFGE followed by Southern blot analysis demonstrated that the blaNDM-5 gene was located on an ∼46-kb plasmid. Plasmid sequences of pNDM-K725, pNDM-CR33, and pNDM-Z214 were almost identical but were slightly different from that of pNDM-Z244. Compared with pNDM-Z244, ΔISAba125 and partial copies of IS3000 were missing. The genetic backgrounds of the blaNDM-5 gene in four strains were slightly different from that of the typical pNDM_MGR194. This study comprehensively characterized the horizontal gene transfer of the blaNDM-5 gene among different Enterobacteriaceae isolates in pediatric patients, and the IncX3-type plasmid was responsible for the spread.IMPORTANCE The emergence of CRE strains resistant to multiple antibiotics is considered a substantial threat to human health. Therefore, all the efforts to provide a detailed molecular transmission mechanism of specific drug resistance can contribute positively to prevent the further spread of multidrug-resistant bacteria. Although the new superbug harboring blaNDM-5 has been reported in many countries, it was mostly identified among E. coli strains, and the gene transfer mechanism has not been fully recognized and studied. In this work, we identified 22 blaNDM-5-positive strains in different species of Enterobacteriaceae, including 16 Klebsiella pneumoniae strains, four Klebsiella aerogenes strains, and two Escherichia coli strains, which indicated the horizontal gene transfer of blaNDM-5 among Enterobacteriaceae strains in pediatric patients. Moreover, blaNDM-5 was located on a 46-kb IncX3 plasmid, which is possibly responsible for this widespread horizontal gene transfer. The different genetic contexts of the blaNDM-5 gene indicated some minor evolutions of the plasmid, based on the complete sequences of the blaNDM-5 plasmids. These findings are of great significance to understand the transmission mechanism of drug resistance genes, develop anti-infection treatment, and take effective infection control measures.

Tian D ，Wang B ，Zhang H ，Pan F ，Wang C ，Shi Y ，Sun Y ... -  《mSphere》

Molecular Epidemiology of Plasmid-Mediated Fosfomycin Resistance Gene Determinants in Klebsiella pneumoniae Carbapenemase-Producing Klebsiella pneumoniae Isolates in China.

Chen J ，Wang D ，Ding Y ，Zhang L ，Li X ... -  《-》

Occurrence and characterisation of ESBL-encoding plasmids among Escherichia coli isolates from fresh vegetables.

Extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates have been increasingly reported in different reservoirs. The aims of this study were to investigate the presence of ESBL-producing E. coli in fresh vegetables and to characterise their ESBL gene-carrying plasmids. Among the 245 samples from vegetables investigated during 2011-2013, seven putative ESBL-producing E. coli (salad n = 2, sprouts n = 5) were found. They were subjected to ESBL phenotypic confirmatory tests, detection/sequencing of ESBL genes, antimicrobial susceptibility testing (AST), phylotyping, XbaI-macrorestriction analysis, multilocus sequence typing and transformation. Transformants were characterised by AST, S1-nuclease PFGE, replicon typing, conjugation and investigated for co-located antimicrobial resistance genes. Two ESBL gene-carrying plasmids were sequenced using a HiSeq 2500 system. The seven isolates were confirmed as ESBL producers, displayed unrelated XbaI-patterns and unique sequence types (STs) and belonged to the phylogroups A, B1 or D. The ESBL genes were located on plasmids. Two plasmids carrying blaCTX-M-14 genes (incompatibility group IncK or IncHI2) were seen in isolates from salad (ST973) and sprout (ST527). Two blaCTX-M-15- (IncFIB; non-typeable) and the IncN blaCTX-M-65- and IncHI2 blaCTX-M-125-carrying plasmids were found in isolates from sprouts (ST410, ST847, ST10, ST542). All plasmids were conjugative, except for the IncFIA-FIB blaCTX-M-2-carrying plasmid. Sequence analysis of two plasmids identified the ESBL genes in close location to other resistance genes: sulfonamide resistance gene sul2, streptomycin resistance genes strA and strB, the plasmid-mediated quinolone resistance gene qnrS1 and blaTEM-1 (sul2-strA-strB-IS66-blaTEM-1-tnpR-ΔtnpA-ISEcp1-blaCTX-M-15-Δorf477-ΔtnpA-qnrS1) or the fosfomycin resistance gene fosA3 (ΔISEcp1-blaCTX-M-125-ΔIS903B-fosA3). These observations underline the importance of vegetables as reservoirs for multidrug resistant ESBL-producing E. coli.

Freitag C ，Michael GB ，Li J ，Kadlec K ，Wang Y ，Hassel M ，Schwarz S ... -  《-》