Molecular and Phylogenetic Characterization of Non-O157 Shiga Toxin-Producing Escherichia coli Strains in China

Abstract

Shiga toxin-producing Escherichia coli (STEC) causes diarrhea and hemorrhagic colitis with life-threatening complications, such as hemolytic uremic syndrome. The aim of this study was to assess the molecular epidemiologic features of non-O157 STEC strains from different resources in China and illustrate the role of animal reservoirs or animal-derived foodstuffs in human STEC infections. A collection of 301 non-O157 STEC isolates from domestic and wild animals (i.e., cattle, goat, pig, yak, pika, and antelope), raw meats (i.e., beef, pork, mutton, chicken, and duck), diarrheal patients, and healthy carriers in different regions of China were selected in this study. Of the 301 analyzed STEC isolates, 67 serogroups, and 118 serotypes were identified; this included some predominant serogroups associated with human disease, such as O26, O45, O103, O111, and O121. Eighteen different combinations of stx subtypes were found. Eleven isolates carried the intimin gene eae, 93 isolates contained ehxA, and 73 isolates carried astA. The prevalence of other putative adhesion genes saa, paa, efa1, and toxB was 28.90% (87), 6.98% (21), 2.31% (7), and 1% (3), respectively. The phylogenetic distribution of isolates was analyzed by multilocus sequence typing (MLST). Ninety-four sequence types were assigned across the 301 isolates. A subset of isolates recovered from yak and pika residing in the similar wild environments, Qinghai-Tibetan plateau, showed similar genetic profiles and more tendencies to cluster together. Isolates from goat and mutton exhibited close genetic relatedness with those from human-derived isolates, providing evidence that transmission may have occurred locally within intraspecies or interspecies, and importantly, from animal reservoirs, or raw meats to humans. Comparing isolates in this study with highly virulent strains by MLST, along with serotyping and virulence profiles, it is conceivable that some of isolates from goat, yak, or raw meats may have potential to cause human diseases.

Diversity of antibiotic‐resistant Shiga toxin‐producing Escherichia coli serogroups in foodstuffs of animal origin in northern India

“…Raw beef had more non‐O157 STEC isolates compared to all other types of foodstuffs (45%) ( χ 2 , p < .1), that was expected given that bovines are the main environmental reservoir of various STEC serogroups, both O157 and non‐O157 serogroups (Karmali et al, ; Synge, ). Our findings agrees with reports obtained from India and the rest of the world indicating that foodstuffs of bovine origin were found to carry higher numbers of STEC, including non‐O157 serogroups (Bai et al, ; Hazarika et al, ; Manna et al, ; Sinha et al, ; Xia et al, ).…”

“…Similarly raw fish isolates vt 1 (four isolates) and vt 2 (three isolates), notably none of the isolates was carrying both of vt 1 and vt 2 genes. Similar results of the carriage of vt 1 and vt 2 (or stx 1 and stx 2 genes) by non-O157 isolates from raw beef (Bai et al, 2016;Sinha et al, 2015;Xia et al, 2010), raw fish (Gupta et al, 2013), raw chicken (Momtaz & Jamshidi, 2013), raw milk (Neher et al, 2015), were reported around the world including Indian subcontinent, in all these reports, no unified association was found between the type of VT gene and the sources of isolates, for example, Sinha et al (2015) found that stx 2 genes were more prevalent in ground beef samples in India, while Bosilevac and Koohmaraie (2011) reported the predominance of stx 1 gene among the STEC isolates in ground beef in the United States. Similar to the results reported in this study, Joris, Pierard, and De Zutter (2011) reported that vt 1 and vt 2 genes were equally harbored by the 18 non-O157 STEC isolates from cattle at slaughter in Belgium.…”

“…STEC O101 and STEC O132 detected in raw fish and raw chicken, respectively, were also reported from the same types of samples in other regions in India (Manna et al, 2010). A total of ONT STEC isolates from various samples were also found to harbor Shiga toxin, ONT STEC isolates have been commonly reported in food samples in India and the rest of the world (Bai et al, 2016;Hazarika et al, 2007;Manna et al, 2010;Sinha et al, 2015;Xia et al, 2010).…”

“…STEC O101 and STEC O132 detected in raw fish and raw chicken, respectively, were also reported from the same types of samples in other regions in India (Manna et al, ). A total of ONT STEC isolates from various samples were also found to harbor Shiga toxin, ONT STEC isolates have been commonly reported in food samples in India and the rest of the world (Bai et al, ; Hazarika et al, ; Manna et al, ; Sinha et al, ; Xia et al, ). Overall, it was suggested that the prevalence of STEC serogroups, including non‐O157 serogroups in food of animal origin may varies and the factors attributing to this variation is related to the settings of geographic locations of where the investigation is conducted (Bosilevac & Koohmaraie, ).…”

Research and molecular characteristic of Shiga toxin‐producingEscherichia coliisolated from sheep carcasses

“…The O26 serogroup bearing the pathotype eae + stx 1 + highlighted in this study was isolated from a patient with HUS (Mora et al 2012) and patients with diarrhoea in China according to the data by Bai et al (2016).…”