Non‐O157 Shiga Toxin‐producing Escherichia coli Isolated from Diarrhoeic Calves in Argentina

Abstract

Faecal samples from 76 diarrhoeic calves belonging to 36 farms located in the Pampas plain, Argentina, were examined for Shiga toxin-producing Escherichia coli (STEC). A total of 15 STEC strains were isolated from 12 (15.8%) calves which came from six different farms. All stx positive strains assayed by PCR were also positives in the Vero cell cytotoxicity test. The majority (60.0%) of the STEC strains carried the stx(1) gene. Twelve (80.0%) of the STEC isolates which belonged to serotypes O5:H- (n = 4), O26:H11 (n = 4), O26:H- (n = 1), O111:H- (n = 2), and O123:H38 (n = 1) were also enterohaemolysin (EHly) positive and carried the gene encoding for intimin (eae). All the stx positive strains were negative for the bfpA gene. Localized adherence to HEp-2 cells were observed in 83.3% of the eae+ STEC strains. STEC belonging to serotype O5:H- showed atypical biochemical properties, including urease production. Urease was also produced by two strains belonging to serotypes O153:H? and non-typeable, respectively. Resistance to three or more antibiotics was observed in 12 (80.0%) of the STEC isolates. Most of the serotypes of STEC recovered in this survey carried virulence traits that are associated with increased human and bovine pathogenicity. The present study shows that highly virulent STEC strains are being shed by diarrhoeic calves from farms located in a high incidence area of human STEC infections.

Enterohaemorrhagic E. coli in veterinary medicine

“…Consistent with these observations a study, albeit without direct comparison to healthy calf VTEC, also reported that most VTEC from calf diarrhoea were eaeA and Vt1 positive (Mainil et al, 1993). Two studies (Pohl et al, 1997;Mercado et al, 2004) also noted that most VTEC from diarrhoeic calves were of EHEC serotypes. However, a study in which VTEC prevalence was highest in healthy calves also demonstrated a higher prevalence of eaeA and Vt1 within healthy calves relative to adults , suggesting these factors promote colonisation in younger animals even in the absence of disease.…”

Functional and Phylogenetic Analysis of ureD in Shiga Toxin-Producing Escherichia coli

“…The E. coli strains used in the MLST analysis were also screened by PCR for the presence of the stx 1 , stx 2 , and eae genes. Primer sequences (30,39,46,48), amplification conditions, and amplicon sizes are listed in Table S3 in the supplemental material. PCR products were electrophoresed on 1% agarose gels, and those reactions with bands of the appropriate size were scored as having the genes present.…”

Potentially Human-Pathogenic Escherichia coli O26 in Norwegian Sheep Flocks

“…coli O26 has been isolated from both healthy and diarrheic animals (13,19,27,32). Although several surveys for E. coli O26 have been conducted, most of these studies have been limited, with small sample sizes, or have focused on isolating STEC O26 and not E. coli O26 in general.…”