Neonatal and post-weaning diarrhea caused by porcine enterotoxigenic Escherichia coli producing F4 adhesin (ETEC:F4) is responsible for important economic losses due to mortality and morbidity. In the beginning of 2014, an increase in the frequency and severity of diarrhea cases from pre-weaning and nursery farms was observed in Québec. The aim of this work was to monitor trends in virulence profiles and antimicrobial resistance (AMR) of pathogenic E. coli isolated from pigs.
More than 800 E. coli isolates from over 1300 clinical cases in pigs that were submitted to the Diagnostic Service of the Faculté de médecine vétérinaire de l’Université de Montréal from 2013 to 2016, were characterized. These isolates were examined by multiplex PCR for the detection of the presence of genes coding for the 12 virulence factors most frequently found in pathogenic E. coli in pigs. Antimicrobial resistance (AMR) was also determined by the standard disk diffusion assay, and demographic and clinical data were gathered.
Our results show a significant increase in prevalence of ETEC:F4 cases during the second quarter of 2014. This increase was due to 2 different virotypes of ETEC:F4: an emerging LT:STb:STa:F4 (3TF4) virotype and the previously predominant LT:STb:F4 (2TF4) virotype. Subsequently, in 2014 and 2015, 3TF4 diarrhea cases remained the most prevalent whereas 2TF4 cases were still frequently observed but to a lesser extent. 3TF4 isolates demonstrated an interesting AMR pattern, most being non-susceptible to enrofloxacin. Overall, multidrug resistant ETEC:F4 isolates, especially 3TF4 isolates, became increasingly more frequent between 2013 and 2016 and potential extremely resistant (XDR) isolates were observed. Even though more studies are needed to characterize isolates of the 3TF4 virotype, our results suggest that a potentially new clone of fluoroquinolone-non-susceptible ETEC:F4 could be emerging in pig production farms in Québec.