Abstract
Background: The emergence and spread of antimicrobial resistance has become a major global public health concern. A component element of this is the spread of the plasmid-encoded extended-spectrum b-lactamase (ESBL) genes, conferring resistance to third-generation cephalosporins. The purpose of this study was to investigate the molecular characteristics of ESBL-encoding genes identified in Escherichia coli cultured from diarrheic patients in China from 2013 to 2014.Materials and Methods: A total of 51 E. coli were confirmed as ESBL producers by double-disk synergy testing of 912 E. coli isolates studied. Polymerase chain reaction (PCR) and DNA sequencing were performed to identify the corresponding ESBL genes. Susceptibility testing was tested by the disk diffusion method. Plasmids were typed by PCR-based replicon typing and their sizes were determined by S1-nuclease pulsed-field gel electrophoresis. Multi-locus sequence typing (MLST) and phylogrouping were also performed. Broth mating assays were carried out for all isolates to determine whether the ESBL marker could be transferred by conjugation.Results: Of the 51 ESBL-positive isolates identified, blaCTX-M, blaTEM, blaOXA, and blaSHV were detected in 51, 26, 3, 1 of these isolates, respectively. Sequencing revealed that 7 blaCTX-M subtypes were detected, with blaCTX-M-14 being the most common, followed by blaCTX-M-79 and blaCTX-M-28. Of the 26 TEM-positive isolates identified, all of these were blaTEM-1 genotypes. All isolates contained one to three large plasmids and 10 replicon types were detected. Of these, IncFrep (n = 50), IncK/B (n = 31), IncFIB (n = 26), IncB/O (n = 14), and IncI1-Ir (n = 8) replicon types were the predominating incompatibility groups. Twenty-six isolates demonstrated the ability to transfer their cefotaxime resistance marker at high transfer rates. MLST typing identified 31 sequence types and phylogenetic grouping showed that 12 of the 51 donor strains belonged to phylogroup B2.Conclusion: This study highlights the diversity of the ESBL producing E. coli and also the diversity of ESBL genes and plasmids carrying these genes in China, which poses a threat to public health.
Highlights
Extended-spectrum β-lactamase (ESBL) producing Escherichia coli are a frequent cause of community- and hospital-acquired infections and one of the leading causative agents of infections worldwide (Hampton, 2013; Nischal, 2014)
We report on the isolation and characterization of a collection of ESBL-producing E. coli isolated from diarrheic patients in China
Fifty-one isolates including 27 from Beijing, 9 from Guangxi province, 9 from Henan province, and 6 from Sichuan province were confirmed as ESBL producers by the double-disk synergy test from 912 E. coli recovered from diarrhea cases
Summary
Extended-spectrum β-lactamase (ESBL) producing Escherichia coli are a frequent cause of community- and hospital-acquired infections and one of the leading causative agents of infections worldwide (Hampton, 2013; Nischal, 2014). The latter emerged in the 1980s as derivatives of TEM (named after the patient Temoneira) and SHV (sulfhydryl reagent variable) enzyme types (Gutkind et al, 2013) The genes encoding these acquired enzymes are associated with plasmids with the potential for horizontal dissemination, and the most widespread ESBL type identified is CTX-M (Gutkind et al, 2013). These ESBL genotypes have spread in a pandemic manner and been associated with outbreaks in hospitals and communities worldwide (Gutkind et al, 2013). The purpose of this study was to investigate the molecular characteristics of ESBL-encoding genes identified in Escherichia coli cultured from diarrheic patients in China from 2013 to 2014
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