Molecular characteristics of extended-spectrum β-lactamase-producing Escherichia coli isolated from the rivers and lakes in Northwest China

BACKGROUND: Extended-spectrum β-lactamases (ESBLs)-producing Escherichia coli (E. coli) isolates in environment water become progressively a potential threat to public health, while the detailed information about the ESBL-producing E. coli isolates in the rivers and lakes in Northwest China is scarce. In the present study, it was aimed to characterize the ESBL-producing E. coli isolated from the surface waters in Northwest China. RESULTS: A total of 2686 E. coli isolates were obtained from eleven rivers and lakes in Northwest China to screen for ESBL producers. Seventy-six (2.8%) isolates were classified as ESBL producers, and phylogenic groups D and A accounted for 59.2% of the ESBL producers. CTX-Ms were the predominant ESBLs genotype, and they were represented by seven bla(CTX-M) subtypes. bla(CTX-M-14) was the most prevalent specific CTX-M gene, followed by bla(CTX-M-9), bla(CTX-M-123), bla(CTX-M-15), bla(CTX-M-27,) bla(CTX-M-1) and bla(CTX-M-65). Moreover, 54 of the 76 ESBL producers carried at least one plasmid-mediated quinolone resistance (PMQR) gene, and aac(6′)-Ib-cr was predominant. The overall occurrence of virulence factors ranged from 1.3% (eae) to 48.7% (traT). Thirty-seven sequence types (STs) were confirmed among the 76 ESBL producers, and the predominant was ST10, which was represented by 10 isolates; importantly, clone B2-ST131, associated with severe infections in humans and animals, was detected three times. CONCLUSION: The prevalence of ESBL-producing E. coli from the rivers and lakes in Northwest China was low (2.8%), and the extraintestinal pathogenic E. coli (ExPEC) pathotype was the most commonly detected on the basis of the virulence factor profiles. 76.3% of ESBL producers harbored more than one β-lactamase gene, and bla(CTX-M-14) was the predominant genotype. Notably, one ST131 isolate from Gaogan Canal simultaneously harbored bla(CTX-M-9), bla(CTX-M-15), bla(CTX-M-123), bla(KPC-2), bla(NDM-1), bla(OXA-2) as well as the PMQR genes qnrA, qnrS and aac(6′)-Ib-cr.