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.