Occurrence, Virulence Characteristics, and Serogroups ofShiga Toxin-Producing Escherichia coli Isolated from Sheep and Goatsin Razavi Khorasan Province, Iran

Background and Aim : Shiga toxin-producing Escherichia coli (STEC) is known as a foodbornepathogen associated with human disease characterized by mild or bloody diarrhea hemorrhagiccolitis and hemolytic uremic syndrome (HUS). The presence of STEC in livestock has beenconsidered a serious risk to public health. The contribution of sheep and goats to the foodproduction systems made them one of the main livestock species in developing countries. Hence,this study aimed to investigate the characteristics of STEC in sheep and goat isolates originatingfrom Razavi Khorasan Province, Iran.Methods : Among ۷۰ faecal samples, isolated from April ۲۰۲۲ to June ۲۰۲۲, a total of ۳۰ (۴۲.۸%)STEC strains were detected. The isolates were obtained from faecal samples of sheep (n=۲۳) andgoats (n=۷) animal hosts. All isolates were subjected to Paton's multiplex-PCR assay to detect themajor virulence genes (stx۱, stx۲, ehxA, eae) of the STEC strains. Then, they were tested for thetop ۱۳ important O-groups by conventional PCR amplification based on the protocol offered bythe EU Reference Laboratory for E. coli and some other important serogroups by different PCRs.Results : Of ۳۰ STEC isolates, ۳۳.۳% harbored stx۱ and stx۲, ۶۳.۳% only stx۱, and ۳.۳% stx۲solely; and ۵۳.۳% of the isolates were positive for ehxA and all the studied STEC (۱۰۰%) werenegative for eae gene. The predominant serogroups were O۱۰۳ (۴۶.۶%), O۱۲۸ (۳۰.۰%), O۵(۱۶.۶%), and O۱۱۳ (۶.۶%) respectively.Conclusion : The occurrence of STEC strains in sheep and goats reported here (۴۲.۸%) is inaccordance with prior studies in Iran that have noted a similar distribution range of STEC in theseanimal sources which is considerable. Furthermore, it could be inferred that the STEC isolatesrelated to sheep and goats are less important for human disease since the genes stx۲ and intimin(eae)—which are well known to have a significant role in severe cases of the disease—were onlydetected in one isolate (۳.۳% for stx۲ solely), and all were negative for intimin gene. Finally, thedetection of O۱۰۳ as the predominant serogroup in sheep and goats (۴۶.۶%), posed anunanticipated and interesting finding that future studies are recommended.

Keywords:

Shiga toxin-producing Escherichia coli , STEC , serogroups , sheep and goats , Iran