Differences in the Propensity of Different Antimicrobial Resistance Determinants to Be Disseminated via Transformation in Campylobacter jejuni and Campylobacter coli

Campylobacter jejuni and Campylobacter coli are leading zoonotic foodborne pathogens, and the drugs of choice for human campylobacteriosis are macrolides (e.g., erythromycin) and fluoro-quinolones. C. jejuni and C. coli are naturally competent for transformation via naked DNA uptake, but potential differences in transformation frequency (TF) for different antimicrobial resistance (AMR) markers remain poorly understood. We determined TFs for resistance to different antibiotics using as recipient a derivative of C. jejuni NCTC 11168 (strain SN:CM) with donor DNA from multidrug-resistant C. jejuni or C. coli. TF for nalidixic acid resistance ranked significantly highest (similar to 1.4 x 10(-3)), followed by resistance to streptomycin and gentamicin. Tetracycline resistance via chromosomal tet(O) was less commonly transferred (similar to 7.6 x 10(-7)), while transformation to erythromycin resistance was rare (<= 4.7 x 10(-8)). We also determined TFs with the contemporary poultry-derived strains C. jejuni FSIS 11810577 and C. coli FSIS 1710488 as recipients. TFs to nalidixic acid and streptomycin resistance remained the highest (similar to 7 x 10(-4)). However, TF for gentamicin resistance was remarkably low in certain recipient-donor combinations, while average TF for erythromycin resistance was noticeably higher (similar to 3 x 10(-6) ) than with SN:CM. Findings from this experimental model provide insights into factors that may impact transformation-mediated transfer of AMR leading to AMR dissemination in the agricultural ecosystem.