Effect of usage / non-usage of antibiotics on virulence profiles of Escherichia coli in pig production

Abstract

Pathogenic Escherichia coli pathogens are responsible for acute profuse diarrhoea in growing pig with resultant high morbidity and mortality. Enterotoxigenic E. coli (ETEC) encoding STa, STb, EAST1 and LT enterotoxins and Shiga toxin E. coli (STEC) encoding Stx2e occur most commonly in pigs. This study investigated the prevalence of ETEC and VTEC virulence genes in two groups of growing pigs (five piglets per group) kept under routine farm management practices. One group was administered antibiotics and the other group received no antibiotics. A total of 241 E.coli strains were isolated in piglets from both groups between 0 and 70 days of age. Virulence genes were detected by PCR in 24.8% (18.2 - 32.7) of the antibiotic group isolates and 43.5% (34.5 - 52.9) of the non-antibiotic group with a significant difference (P = 0.002). The proportions of the virulence genes STa, STb, EAST1 and Stx2e were 18.1% (8.61 - 34.39), 0% (0.0 - 10.43), 78.7% (62.25 - 89.32) and 3% (0.53 - 15.32) in the antibiotic group respectively, and 14.8% (7.40 - 27.68), 8.5% (3.36 - 19.93), 85.1% (72.32 - 92.59) and 12.7% (5.98 - 25.17) in the non-antibiotic group respectively. AIDA1 was the most dominant non-fimbrial adhesion factor while F6 was the only fimbrial factor detected. Twelve pathotypes were identified, with pathotype EAST1 being the most prevalent. The study showed that usage/non-usage of antibiotics in growing pigs does not prevent occurrence of disease causing virulence genes and other factors may be involved.