Prevalence and characteristics of ST131 clone among unselected clinical Escherichia coli in a Chinese university hospital

Bin Li,Qingwen He,Yanfang Lu,Chen Li,Fangjun Lan,Yingping Cao

doi:10.1186/s13756-017-0274-0

Abstract

BackgroundEscherichia coli clinical sequence type 131 (ST131) has emerged as an extensively antimicrobial resistant E. coli clonal group in recent years throughout the world. The aim of this study was to investigate the prevalence and molecular characteristics of ST131 among unselected E. coli clinical isolates in a Chinese university hospital.MethodsSeven hundred consecutive E. coli isolates were collected at a Chinese university hospital between 2014 and 2015. Isolates belonging to ST131 were identified by PCR and multilocus sequence typing (MLST), and then characterized for antibiotic resistance, CTX-M-type extended-spectrum β-lactamase genes, fluoroquinolone resistance genes, O types, phylogenetic groups, virulence factors and PFGE patterns.ResultsOverall, 83 (11.6%) isolates were identified as ST131 group. The H30 lineage accounted for 53 (63.9%) of the ST131 isolates, including 13 H30-Rx and 40 H30 non-Rx. The remaining 30 isolates belonged to H41 lineage. Two O types were identified in this study: O25b (66.3%) and O16 (33.7%). Compared with O25b-B2-ST131 isolates, O16-B2-ST131 isolates harbored less virulence factors of adhesins. ST131 H30 Rx isolates had significantly higher virulence score than those of other isolates. O16-B2-ST131 isolates were shown to have a lower resistance to quinolones than O25b-B2-ST131 isolates. 5 nonsynonymous mutations (GyrA S83 L, D87N, ParC S80I, E84V and ParE I529L) were strongly associated with ST131 H30 and O25b isolates. Results of PFGE demonstrated that these isolates were classified into 68 pulsotypes and these subtypes were grouped into 23 different PFGE clusters using 70% similarity cut-off value.ConclusionsThis is the first study to reveal the prevalence and molecular characteristic of ST131 clonal group among consecutive clinical E. coli isolates in China. Our findings demonstrated that ST131 lineage accounts for a small proportion of clinical E. coli isolates in China, which included two major groups: O25b-B2-ST131 and O16-B2-ST131. Our results implies that O16-B2-ST131 subclone may be an important type of E. coli ST 131 in China, which suggests that future studies should not ignore such clone in this country.

Highlights

Escherichia coli clinical sequence type 131 (ST131) has emerged as an extensively antimicrobial resistant E. coli clonal group in recent years throughout the world
All the non-O25b, non-O16 and non-phylogenetic group B2 ST131 strains would be confirmed by multilocus sequence typing (MLST) to be ST131 according to the Achtman scheme using seven housekeeping genes
Prevalence of ST131 and its subclones In total, 83 (11.6%) of the 700 clinical E. coli isolates were identified as ST131

Summary

Introduction

Escherichia coli clinical sequence type 131 (ST131) has emerged as an extensively antimicrobial resistant E. coli clonal group in recent years throughout the world. Escherichia coli sequence type 131 (E. coli ST131) was identified among extended-spectrum β-lactamases (ESBL)producing isolates in Asia, Europe and North America in 2008, and has rapidly emerged globally to become an important pathogen causing various infections in humans [1, 2]. All E. coli ST131 isolates contain the fimH gene with high level of allelic diversity and fimH30 is the most common one [1]. E. coli ST131 isolates are often resistant to fluoroquinolones and produce ESBL [4,5,6]. The H30 subclone comprises most of the fluoroquinolone-resistant ST131 isolates [4]

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