Emergence of macrolide-resistant Campylobacter strains in chicken meat in Poland and the resistance mechanisms involved.

In this study, we investigated the molecular mechanisms involved in erythromycin resistance in the first resistant Campylobacter strains isolated from chicken meat in Poland, and analyzed their genetic relatedness. A total of 297 samples of raw chicken meat and giblets from retail trade in the Warsaw area collected between 2006 and 2009 were examined. Among 211 Campylobacter strains (52 C. jejuni and 159 C. coli), 10 C. coli isolates (4.7%) were resistant to erythromycin. All the C. jejuni strains were susceptible. Among the high-level macrolide-resistant isolates, two different point mutations within the domain V of the 23S rRNA gene were observed. Eight of the strains had adenine→guanine transitions at position 2075, two other isolates at position 2074. Sequence analysis of ribosomal proteins L4 (rplD) and L22 (rplV) indicated that ribosomal protein modifications did not contribute to macrolide resistance. A mutation in the inverted repeat in the cmeR and cmeABC intergenic region was found in a single resistant strain. The genetic relatedness of Campylobacter isolates showed that two resistant strains obtained from the same production plant in a 2-month interval were genetically identical. The risk of transmission of resistant strains via the food chain highlights the need for constant monitoring of resistance in Campylobacter isolates of human and animal hosts.