Non-O157 Shiga toxin-producing Escherichia coli with potential harmful profiles to humans are isolated from the faeces of calves in Uruguay

Abstract

Shiga toxin-producing Escherichia coli (STEC) infections are responsible for acute illnesses and deaths in humans. Cattle and humans are exposed to STEC through faeces and contaminated food and water. The big six and O157 STEC serogroups are important food and water-borne human pathogens. Additionally, Stx1a, Stx2a and Stx2c subtypes are highly associated with the haemolytic uremic syndrome. This study aimed to determine Shiga toxin-subtypes, the presence of antigen 43 families, the genotypic and phenotypic antimicrobial susceptibility profiles, O-serogrouping, phylotypes and phylogenetic relatedness of STEC of calf origin. Sixteen STEC isolates from calf origin were analysed. PCR was performed to determine Stx subtypes, serogroups, the presence of ag43 I and II and phylotypes. The antimicrobial profile was evaluated and the presence of PMQR and fosfomycin genes was determined by PCR. The clonal relatedness of STEC was studied by PFGE. The genotypes stx1a+c, stx1a+, stx1a+/stx2e+, stx1a+c/stx2e and stx2a were detected. Ag43 II was the most prevalent among subfamilies. STEC isolates were serotyped as O103 (n=5) and O111 (n=6). Fifty per cent of the isolates were classified as B1 phylogroup, 4/16 as E, 1/16 as C, and 1/16 as F. Non-O157 STEC isolates showed a high level of diversity, independent of the geographical and farm-origin. Isolates were resistant to ampicillin, ciprofloxacin, gentamicin, and fosfomycin-trometamol. The gene fosA7 was detected in 1 isolate. The virulence profiles, including Shiga toxin-subtypes and serogroups, denote the potential harm of non-O157 STEC isolates to humans. We also confirmed that circulating non-O157 STEC from cattle present genetic heterogeneity and are susceptible to antibiotics.