An investigation of the presence of Escherichia coli O149:K91:F4 on pig farms in southern Ontario and the use of antimicrobials and risk factors associated with the presence of this serogroup.

Prevalence, causative factors, treatment, and preventative measures for O149:K91:F4 Escherichia coli infection of postweaning pigs was determined by using a cross-sectional study including 70 farms in Ontario. Surveys were distributed and samples cultured bacteriologically, resulting in 30% of farms testing positive to E. coli 0149:K91:F4. Possible causative factors, such as housing or nutrition, were not significantly different between positive and negative farms. Use of injectable antibiotics (P = 0.05) and zinc oxide (P = 0.003) was higher on E. coli O149:K91:K88 (F4)-positive farms. A higher level of biosecurity and the presence of other diseases may be associated with an increased risk of isolating E. coli O149:K91:F4 from weanling pigs.