Campylobacter in organic and conventional pig productions in France: occurrence, antibiotic resistance and genetic diversity

Summary

The objectives of this study were to assess the occurrence of Campylobacter in organic and conventional pig productions, and to evaluate their antimicrobial resistance and genetic diversity in these two productions.
Sampling was realized in one slaughterhouse: 31 organic herds and 31 conventional herds were considered. Detection of Campylobacter was done on respectively 56 and 58 organic and conventional pig colon contents, and on 60 carcass swabs for each production. Campylobacter strains were studied for their resistance to 8 antibiotics and for their genetic diversity through PFGE using KpnI enzyme.
Occurrence in colon content was not significantly different between organic (76.8%) and conventional pigs (74.0%). Only one conventional carcass was contaminated by Campylobacter. All the Campylobacter were C. coli.
A total of 266 C. coli were characterized: 138 and 124 from colon content of organic and conventional pigs, respectively, and 4 from carcass. Only 10 isolates were pansusceptible. The most frequent resistance profile was resistance to streptomycin with tetracycline (24.2% and 33.3% of the isolates from conventional and organic pigs, respectively). Isolates from conventional pigs were significantly more frequently resistant to tetracycline and erythromycin, often in association with other resistances: 53.1% of isolates from conventional pigs were resistant to 3 or more antibiotics families compared to 26.8% from organic pigs.
The 240 typable isolates were distributed in 122 KpnI profiles. Only one KpnI profile was common for 1 organic and 1 conventional isolates. Index of diversity was very high (ID>0.98) in both productions.
This study showed that occurrence and diversity of Campylobacter in organic and conventional pigs are similar. The lower level of antibiotic resistance for organic pigs may be related to the restricted use of antibiotics in this production and / or colonization of organic pigs with susceptible environmental strains.