title: Prevalence and Molecular Characteristics of Extended-Spectrum β-Lactamase Genes inEscherichia coliIsolated from Diarrheic Patients in China.
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 inEscherichia colicultured from diarrheic patients in China from 2013 to 2014.Materials and Methods:A total of 51E. coliwere confirmed as ESBL producers by double-disk synergy testing of 912E. coliisolates 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 blaSHVwere detected in 51, 26, 3, 1 of these isolates, respectively. Sequencing revealed that 7 blaCTX-Msubtypes were detected, with blaCTX-M-14being the most common, followed by blaCTX-M-79and blaCTX-M-28. Of the 26 TEM-positive isolates identified, all of these were blaTEM-1genotypes. 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 producingE. coliand also the diversity of ESBL genes and plasmids carrying these genes in China, which poses a threat to public health.
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment Beijing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Bai
authors.affiliation: Institute for Nutrition and Food Hygiene, Beijing Key Laboratory of Diagnostic and Traceability Technologies for Food Poisoning, Beijing Center for Disease Prevention and Control Beijing, China.
authors.forename: Lili
authors.initials: L
authors.lastname: Wang
authors.affiliation: Center for Disease Control and Prevention of Sichuan Province Sichuan, China.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Yang
authors.affiliation: College of Veterinary Medicine, Northwest A&F University Xianyang, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment Beijing, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Gan
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment Beijing, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment Beijing, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Xu
authors.affiliation: Institute for Nutrition and Food Hygiene, Beijing Key Laboratory of Diagnostic and Traceability Technologies for Food Poisoning, Beijing Center for Disease Prevention and Control Beijing, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
authors.affiliation: School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney NSW, Australia.
authors.forename: Ruiting
authors.initials: R
authors.lastname: Lan
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk AssessmentBeijing, China; UCD-Centre for Food Safety, School of Public Health, Physiotherapy and Sports Science, University College DublinBelfield, Ireland.
authors.forename: Séamus
authors.initials: S
authors.lastname: Fanning
authors.affiliation: Key Laboratory of Food Safety Risk Assessment, Ministry of Health, China National Center for Food Safety Risk Assessment Beijing, China.
authors.forename: Fengqin
authors.initials: F
authors.lastname: Li
keywords: China; Escherichia coli; S1 nuclease digestion; conjugation; extended-spectrum β-lactamase genes; horizontal gene transfer; human