Purpose: Given that roxarsone was voluntarily withdrawn from the market in 2011, we hypothesized that Campylobacter isolated from retail carcasses after 2011, will not possess the arsenic resistance genes observed in those isolated before 2011.
Methods: Thirteen Campylobacter isolates from retail chickens, organic and conventional, were screened for arsenic resistance. PCR primer sets specific for the arsenic resistance genes arsC, acr3, arsB, arsP, and arsR were used to determine the presence/absence of these genes in the isolates.
Results: Campylobacter was isolated from thirteen of thirty-four chickens purchased and sampled in 2013 (38%). Four of the isolates came from conventionally reared birds, while nine came from free-range, organically reared birds. Of the thirteen isolates, three possessed the arsenic resistance genes arsC and acr3, which regulate arsenate reduction and arsenite excretion, respectively. Two of the three isolates possessing these genes were isolated from conventionally reared birds. Only one of the thirteen isolates, a free range isolate, possessed the arsR gene. It was also one of the three isolates to possess arsC and acr3. Five isolates, three from organic and two from conventional, contained arsP, and, only one, a conventionally reared bird, also contained arsC and acr3. Five isolates possessed arsB, which is separate from the ars operon and can contribute to arsenite resistance. Of these five isolates, four were organic.
Significance: From our results, it is clear that arsenic resistance genes persist in poultry isolates of Campylobacter spp., even though the selection pressure has been removed. This indicates that these resistance genes do not pose a fitness burden on the organism and further research into their fitness impact should be undertaken.