Antimicrobial susceptibilities and resistance genes in Campylobacter strains isolated from poultry and pigs in Australia.

AIMS

To evaluate the phenotypic and genotypic profiles of Campylobacter spp. from poultry faecal samples from free range or intensively raised meat chickens and free range egg layers. In addition, a case-comparison study of antibiotic resistance genes from different groups of poultry and some pig strains previously collected was carried out.

METHODS

Resistance to different antibiotics was assessed using the agar dilution method. In addition, all the strains were tested for ampicillin (bla(OXA-61) ), erythromycin (aph-3-1), tetracycline tet(O), streptomycin (aadE), and the energy-dependent multi-drug efflux pump (cmeB) resistance genes using multiplex polymerase chain reaction.

RESULTS

The evaluation of phenotypic resistance revealed all of the strains from poultry were sensitive to ciprofloxacin, gentamicin, erythromycin or tylosin. But, widespread resistance to lincomycin (51-100%), extensive resistance to ampicillin (33·3-60·2%) and less resistance to tetracycline (5·6-40·7%) were observed in the different groups of chickens. Antibiotic resistance genes bla(OXA-61,) cmeB and tet(O) were found in 82·6-92·7%, 80·3-89% and 22·3-30·9% Camp. coli isolates from pigs, whilst 59-65·4% and 19·2-40·7% Camp. jejuni from chickens were found to encode bla(OXA-61) and tet(O), respectively.

CONCLUSION

No significant difference between isolates from free range egg layers and meat chickens (P < 0·05) was found. However, there were significant differences between the pig strains and all the groups of poultry strains (P < 0·05) with regard to carriage of resistance genes. In addition, pulsed field gel electrophoresis of selected resistant isolates from the poultry and pig revealed closely related clonal groups.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our results suggest the resistant strains are persisting environmental isolates that have been acquired by the different livestock species. Furthermore, the different treatment practices in poultry and pigs have resulted in differences in resistance profiles in Campylobacter isolates.