Molecular serotyping of Shiga toxin-producing Escherichia coli (STEC) of animal origin in Iran reveals the presence of important non-O۱۵۷ seropathotypes

The present study reported the first serotyping (O:H typing) data documented in Shiga toxin-producing Escherichia coli (STEC) strains of animal origin in Iran in isolates recovered between ۲۰۰۸ to ۲۰۱۶. A total number of ۷۵ STEC strains previously isolated from fecal samples of cattle, sheep, goats, pigeons, humans, and deer were assessed by different polymerase chain reaction (PCR) assays detecting the major virulence genes of STEC and phylogroups. Then, the strains were tested for the ۱۶ important O-groups by PCR. Finally, twenty strains were selected for H-genotyping by PCR plus sequencing. The predominant serogroup was O۱۱۳ which was detected in nine isolates (five cattle, ۵۵.۵۰%; two goats, ۲۲.۲۰%; two red deer, ۲۲.۲۰%) followed by O۲۶ (۳/۳, ۱۰۰%) in cattle, O۱۱۱ (۳/۳, ۱۰۰%) in cattle, O۵ (۳/۳, ۱۰۰%) in sheep, O۶۳ (۱/۱, ۱۰۰%) in pigeon, O۷۵ (۲/۲, ۱۰۰%) in pigeons, and O۱۲۸ in goats (۲/۳, ۶۶.۶۰%) and pigeon (۱/۳, ۳۳.۳۰%). The most important recognized serotypes were O۱۱۳:H۲۱ in cattle (۲/۳) and goat (۱/۳), O۱۱۳:H۴ in red deer (۱/۱), O۱۱۱:H۸ in calves (۲/۲), O۲۶:H۱۱ in calve (۱/۱), O۱۲۸:H۲ in goats (۲/۳) and pigeon (۱/۳), and O۵:H۱۹ in sheep (۳/۳). One cattle strain carrying stx۱, stx۲, eae, and Ehly genes belonged to O۲۶:H۲۹ serotype. Most strains with determined O-groups were from the bovine source that highlighted the importance of cattle as reservoirs of potentially pathogenic serovars. The present study suggested that the top seven non-O۱۵۷ serogroups should be assessed along with O۱۵۷ in all future research and clinical diagnostics of STEC in Iran.

Keywords:

Animals , Iran , Serotypes , STEC , Typing