The emergence of blaCTX-M-15-carrying Escherichia coli of ST131 and new sequence types in Western China

Abstract

Background: blaCTX-M-15, the most widely distributed gene encoding extended-spectrum β-lactamases globally, was not common in China. This study was performed to characterize blaCTX-M-15-carrying Escherichia coli in western China. Findings: Out of 144 Escherichia coli isolates from 20 hospitals in western China, 8 were found carrying blaCTX-M-15. blaCTX-M-15 was carried by isolates of ST131and 5 new STs (ST3342, ST3513, ST3516, ST3517 and ST3518). The 5 new STs shared 5 identical alleles out of 7 but only had up to 2 alleles identical to ST131. blaCTX-M-15 was located on plasmids of IncI1 (ST16) or IncFII-related group (four replicon types). The co-transfer of a few antimicrobial resistance genes including qnrA, qnrB, qnrS, qepA, aac (6′)-Ib-cr, aac (3)-II, tetA, blaTEM and blaOXA-1 with blaCTX-M-15 were examined but only blaTEM-1 was found co-transferring with blaCTX-M-15.Conclusions: Five new STs of E. coli and three new types of IncFII-related plasmids carrying blaCTX-M-15 were identified. This study together with several reports suggested that blaCTX-M-15 has emerged in China and the interruption of both vertical and horizontal transmission of blaCTX-M-15 is required to hurdle its further spread. © 2013 Zhang et al.; licensee BioMed Central Ltd.