Antibiotic resistance in Campylobacter jejuniand Campylobacter coli:significant contribution of an RND type efflux pump in erythromycin resistance

AbstractIn this study, we aimed to determine the antibiotic resistance status of Campylobacterspp. isolated from human infections in our region, including the role of mechanisms involved in erythromycin resistance. Standard methods were used for the isolation, identification and antibiotic susceptibility testing of Campylobacterspp. isolates. Erythromycin-resistant mutants were selected from erythromycin-susceptible clinical isolates, and the erythromycin resistance mechanisms were investigated phenotypically by determining the erythromycin MICs of isolates in the presence and absence of the resistance nodulation cell division (RND) type efflux pump inhibitor, phenylalanine-arginine β-naphthylamide dihydrochloride (PAβN), and genotypically by determining ribosomal and cmeABCalterations using PCR and DNA sequence analysis. Campylobacterspp., including 184 C. jejuniand 20 C. coliin a two-year period, were the most frequently isolated gastrointestinal bacterial pathogens in our region. However, in both C. jejuniand C. coli,resistance to tetracycline and ciprofloxacin were found to be high, erythromycin resistance was especially high (20%) in C. coli. With a ribosomal alteration, A2075G, which was found to be associated with high-level erythromycin resistance in clinical isolates, PAβN significantly reduced the erythromycin MICs in both clinical isolates and mutants. An important finding of this study, while considering cmeABCoperon, is the explanation of why erythromycin resistance is more common among C. colithan C. jejuni,bearing in mind the specific deletions and alterations in the intergenic region of the operon in all erythromycin-resistant C. coliisolates. Ultimately, these findings revealed the significant role of RND-type efflux activity in increased erythromycin MICs of the isolates.