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

Abstract

Campylobacter jejuni and Campylobacter coli are leading zoonotic foodborne pathogens, and the drugs of choice for human campylobacteriosis are macrolides (e.g., erythromycin) and fluoroquinolones. 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 (~1.4 × 10−3), followed by resistance to streptomycin and gentamicin. Tetracycline resistance via chromosomal tet(O) was less commonly transferred (~7.6 × 10−7), while transformation to erythromycin resistance was rare (≤4.7 × 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 (~7 × 10−4). However, TF for gentamicin resistance was remarkably low in certain recipient–donor combinations, while average TF for erythromycin resistance was noticeably higher (~3 × 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.

Genomic Analysis Points to Multiple Genetic Mechanisms for Non-Transformable Campylobacter jejuni ST-50

“…Our study along with others [20,24] establishes that the transfer of AMR determinants through natural transformation is markedly more frequent, by several orders of magnitude, than the occurrence of mutations leading to resistance. Although most natural transformation studies are performed in vitro using purified donor DNA [16,20,24], it is noteworthy that natural transformation has been demonstrated in vivo within chickens and turkeys, which are prevalent hosts for this pathogen [31,32].…”

“…The ability to acquire and recombine DNA between strains of C. jejuni and C. coli plays a significant role in the genetic diversity of C. jejuni and C. coli , including the movement of chromosomal AMR markers in these species [ 9 , 16 , 30 ]. Our study along with others [ 20 , 24 ] establishes that the transfer of AMR determinants through natural transformation is markedly more frequent, by several orders of magnitude, than the occurrence of mutations leading to resistance. Although most natural transformation studies are performed in vitro using purified donor DNA [ 16 , 20 , 24 ], it is noteworthy that natural transformation has been demonstrated in vivo within chickens and turkeys, which are prevalent hosts for this pathogen [ 31 , 32 ].…”

“…The transformation assays were determined as previously described [ 24 ]. Briefly, DNA was extracted from donor strains C. jejuni 14980A and C. coli 14983A using the Qiagen DNeasy Blood and Tissue Kit (Qiagen, Redwood City, CA, USA), and was used for transformation of C. jejuni and C. coli , respectively, to nalidixic acid resistance (Nal R ), or to streptomycin resistance (Str R ) when the recipient was already Nal R [ 25 ].…”

“…The mutation frequency was calculated as the ratio of total CFUs in the control spot without added DNA on MHA supplemented with the appropriate antibiotic over the total CFUs on MHA with no antibiotic. All transformation assays included as a control C. jejuni Cj0264c ::Cm, a derivative of C. jejuni NCTC 11168, that was confirmed to be readily transformable to Nal R and Str R using DNA from the donors employed here [ 24 ].…”

Cj0683 Is a Competence Protein Essential for Efficient Initialization of DNA Uptake in Campylobacter jejuni

“…C. jejuni displays a high genetic diversity due to its natural transformation capacity. This leads to an increase of the bacterium’s adaptive potential resulting in successful survival including the acquisition of antimicrobial resistances [ 4 , 5 , 6 , 7 ]. A prerequisite of natural transformation is the capacity to take up DNA from the environment.…”