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

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.

Prevalence and characteristics of Shiga toxin-producing Escherichia coli isolated from retail raw meats in China

“…In China, STEC O157:H7 were detected in different aminals and caused a major outbreak in 1999 Xiong et al, 2012). Our previous studies showed that healthy pigs and yaks are reservoirs of non-O157 STEC in China (Bai et al, 2013;Meng et al, 2014). Both O157:H7 and non-O157 STEC strains have been isolated from outpatients with acute diarrhoea in southeastern China (Chen et al, 2014), and from ratail meats including pork, mutton and beef in Shandong, China (Koitabashi et al, 2008).…”

“…Besides, many other virulence and adherence factors are involved in STEC pathogenicity (Bai et al, 2013;Meng et al, 2014).…”

“…The supernatant was centrifuged at 13,000 ×g for 2 min and the pellet was suspended in 100 μl lysis buffer (100 mM NaCl, 10 mM Tris-HCl [pH 8.3], 1 mM EDTA [pH 9.0], and 1% Triton X-100), boiled for 10 min, and centrifuged. The resulting supernatant was used as a template to test the presence of stx 1 and stx 2 by duplex PCR (Bai et al, 2013).…”

“…The O:H serotype of each isolate was determined by methods as previously described (Bai et al, 2013;Meng et al, 2014).…”

“…The stx 1 and/or stx 2 subtypes of all STEC isolates were determined by a PCR-based subtyping method, and then confirmed by suquencing the complete stx 1 and/or stx 2 genes of certain STEC isolates according to previously reported methods (Bai et al, 2013;Meng et al, 2014).…”