Abstract
Shiga toxin-producing Escherichia coli (STEC) are an emerging group of zoonotic pathogens. Ruminants are the natural reservoir of STEC. In this study we determined the prevalence and characteristics of the STEC in plateau pika (Ochotona curzoniae) on the Qinghai-Tibetan Plateau, China. A total of 1116 pika samples, including 294 intestinal contents samples, 317 fecal samples, and 505 intestinal contents samples, were collected from May to August in the years 2012, 2013, and 2015, respectively. Twenty-one samples (1.88%) yielded at least one STEC isolate; in total, 22 STEC isolates were recovered. Thirteen different O serogroups and 14 serotypes were identified. One stx1 subtype (stx1a) and three stx2 subtypes (stx2a, stx2b, and stx2d) were present in the STEC isolates. Fifteen, fourteen, and three STEC isolates harbored the virulence genes ehxA, subA, and astA, respectively. Adherence-associated genes iha and saa were, respectively, present in 72.73 and 68.18% of the STEC isolates. Twenty antibiotics were active against all the STEC isolates; all strains were resistant to penicillin G, and some to cephalothin or streptomycin. The 22 STEC isolates were divided into 16 pulsed-field gel electrophoresis patterns and 12 sequence types. Plateau pikas may play a role in the ongoing circulation of STEC in the Qinghai-Tibetan plateau. This study provides the first report on STEC in plateau pikas and new information about STEC reservoirs in wildlife. Based on the serotypes, virulence gene profiles and multi-locus sequence typing (MLST) analysis, the majority of these pika STECs may pose a low public health risk.
Highlights
Shiga toxin-producing Escherichia coli (STEC) represents an emerging group of zoonotic pathogens causing diarrhea, hemorrhagic colitis (HC), and the life-threatening hemolytic uremic syndrome (HUS) in humans (Smith et al, 2014)
Single isolate was obtained from 19 intestinal content samples and one fecal sample
We found that 5.2% (58/1116) of the plateau pika samples were positive for the stx genes by PCR and 1.88% (21/1116) by microbiological culture
Summary
Shiga toxin-producing Escherichia coli (STEC) represents an emerging group of zoonotic pathogens causing diarrhea, hemorrhagic colitis (HC), and the life-threatening hemolytic uremic syndrome (HUS) in humans (Smith et al, 2014). There is growing concern over the emergence of more than 200 non-O157 STEC serotypes associated with human illness, including the life threatening HUS (Coombes et al, 2008). Many non-O157 strains that produce Shiga toxin have been not associated with HUS cases, indicating additional virulence determinants may play a role in pathogenesis. Enterohemolysin (EhxA), encoded by a 60-MDa virulence plasmid in some STEC strains, that readily causes hemolysis of washed sheep erythrocytes, is another important virulence factor that contributes to severe disease in humans (Cookson et al, 2007). A number of other adherence structures and virulence factors have been proposed to contribute to STEC pathogenesis (Coombes et al, 2008; Tseng et al, 2014; Chui et al, 2015)
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