Shiga Toxin-Producing Escherichia coli in Yaks (Bos grunniens) from the Qinghai-Tibetan Plateau, China

Xiangning Bai,Dong Jin,Shan Lu,Qiong Meng,Jianguo Xu,Youquan Xin,Ailan Zhao,Hui Sun,Ruiting Lan,Yanwen Xiong,Hui Xie,Bo Yu,Xiaofeng Ren

doi:10.1371/journal.pone.0065537

Abstract

Shiga toxin (Stx)-producing Escherichia coli (STEC) are recognized as important human pathogens of public health concern. Many animals are the sources of STEC. In this study we determined the occurrence and characteristics of the STEC in yaks (Bos grunniens) from the Qinghai-Tibetan plateau, China. A total of 728 yak fecal samples was collected from June to August, 2012 and was screened for the presence of the stx 1 and stx 2 genes by TaqMan real-time PCR after the sample was enriched in modified Tryptone Soya Broth. Of the 138 (18.96%) stx 1 and/or stx 2-positive samples, 85 (61.59%) were confirmed to have at least 1 STEC isolate present by culture isolation, from which 128 STEC isolates were recovered. All STEC isolates were serotyped, genotyped by pulsed-field gel electrophoresis (PFGE) and characterized for the presence of 16 known virulence factors. Fifteen different O serogroups and 36 different O:H serotypes were identified in the 128 STEC isolates with 21 and 4 untypable for the O and H antigens respectively. One stx 1 subtype (stx 1a) and 5 stx 2 subtypes (stx 2a, stx 2b, stx 2c, stx 2d and stx 2g) were present in these STEC isolates. Apart from lpfA O157/OI-141, lpfA O157/OI-154, lpfA O113, katP and toxB which were all absent, other virulence factors screened (eaeA, iha, efa1, saa, paa, cnf1, cnf2, astA, subA, exhA and espP) were variably present in the 128 STEC isolates. PFGE were successful for all except 5 isolates and separated them into 67 different PFGE patterns. For the 18 serotypes with 2 or more isolates, isolates of the same serotypes had the same or closely related PFGE patterns, demonstrating clonality of these serotypes. This study was the first report on occurrence and characteristics of STEC isolated from yaks (Bos grunniens) from the Qinghai-Tibetan plateau, China, and extended the genetic diversity and reservoir host range of STEC.

Highlights

Shiga toxin-producing Escherichia coli (STEC) are recognized globally as major food-borne pathogens
In 2011, Germany experienced the largest outbreak of non-O157 STEC, O104:H4, ever recorded with 3,816 cases including 845 hemolytic uremic syndrome (HUS) cases and 54 deaths, similar outbreaks were reported in France and other counties in Europe subsequently [9,10,11,12]
Prevalence of STEC in Yak Fecal Samples Out of 728 yak fecal samples analyzed in this study, 138 (18.96%) were positive for stx1and/or stx2 genes using TaqMan real-time PCR assay

Summary

Introduction

Shiga toxin-producing Escherichia coli (STEC) are recognized globally as major food-borne pathogens. Clinical manifestations of STEC infections in humans range from non-bloody diarrhea to hemorrhagic colitis (HC) and sometimes fatal hemolytic uremic syndrome (HUS) complications. O157:H7 is the most frequently encountered STEC in human infections [2]. Many outbreaks and sporadic infections caused by STEC O157:H7/NM have been reported in different regions of the world [3,4,5,6,7,8]. Non-O157 STEC isolates have been increasingly associated with human infections and outbreaks. In 2011, Germany experienced the largest outbreak of non-O157 STEC, O104:H4, ever recorded with 3,816 cases including 845 HUS cases and 54 deaths, similar outbreaks were reported in France and other counties in Europe subsequently [9,10,11,12]. Non-O157 STEC infections are likely to be under-reported due to awareness and difficulties in isolation and identification in clinical laboratories

Methods

Results

Conclusion