Prevalence of antimicrobial resistance and association with toxin genes in Clostridium difficile in commercial swine.

OBJECTIVE To estimate prevalence and determine association between antimicrobia resistance and toxin gene profile of Clostridium difficile in commercial pigs at the preharvest food-safety level. ANIMALS 68 sows and 251 young pigs from 5 farms in North Carolina and 3 in Ohio. PROCEDURES Fecal samples were collected from sows (8/farm) and matched young pigs (32/farm) at farrowing and again at the nursery and finishing stages. Clostridium difficile isolates were tested for susceptibility to 6 antimicrobials. A PCR assay was used to detect genes coding for enterotoxin A (tcdA), cytotoxin B (tcdB), and binary toxin (cdtB). RESULTS C difficile prevalence in young pigs at farrowing was 73% (n=183) with significantly higher prevalence in Ohio (875%) than in North Carolina (64%). Clostridium difficile was isolated from 32 (47%) sows with no significant difference between the 2 regions. A single pig had a positive test result at the nursery, and no isolate was recovered at the finishing farms. Resistance to ciprofloxacin was predominant in young pigs (91.3% of isolates) and sows (94%). The antimicrobial resistance profile ciprofloxacin-erythromycin-tetracycline was detected in 21.4% and 11.7% of isolates from young pigs and sows, respectively. Most isolates had positive results for tcdA (65%), tcdB (84%), and the binary toxin cdtB (77%) genes. Erythromycin resistance and tetracycline resistance were significantly associated with toxin gene profiles. CONCLUSIONS AND CLINICAL RELEVANCE The common occurrence of antimicrobial-resistant C difficile and the significant association of toxigenic strains with antimicrobial resistance could contribute to high morbidity in farms with farrowing pigs.