Emergence of lnu(C) variant conferring lincomycin resistance in Campylobacter coli of chicken origin

Area of Science:

• Veterinary Microbiology
• Antimicrobial Resistance
• Foodborne Pathogens

Background:

• Lincomycin is vital in veterinary medicine, particularly for food animals.
• Campylobacter species are significant foodborne pathogens responsible for campylobacteriosis.
• Lincosamide resistance in Campylobacter is rare, with Erm(B) previously being the only identified mechanism.

Purpose of the Study:

• To identify novel mechanisms of lincomycin resistance in Campylobacter.
• To characterize a newly discovered lincomycin resistance gene in chicken-derived Campylobacter.
• To investigate the genetic context and dissemination potential of this resistance gene.

Main Methods:

• Identification and sequencing of a novel lnu(C) gene variant in Campylobacter.
• Functional validation of the lnu(C) variant through gene cloning and susceptibility testing.
• Genomic analysis to determine the location and surrounding genetic elements of the lnu(C) variant.
• Phylogenetic analysis to assess the distribution of the lnu(C) gene in Campylobacter coli.

Main Results:

• A variant of the lnu(C) gene, conferring lincomycin resistance, was identified in Campylobacter of chicken origin.
• The identified Lnu(C) protein exhibited specific amino acid substitutions compared to the reference.
• Cloning the lnu(C) variant into Campylobacter jejuni resulted in a 32-fold increase in Minimum Inhibitory Concentrations (MICs) for lincomycin.
• The lnu(C) variant was found within an MTnSag1-like transposon, inserted between specific chromosomal genes.
• The lnu(C) gene was detected globally in Campylobacter coli across various sequence types (STs).

Conclusions:

• The identified lnu(C) gene variant is a significant contributor to lincomycin resistance in Campylobacter.
• While transposition was not observed, horizontal gene transfer via natural transformation may facilitate the spread of this resistance.
• The presence and potential dissemination of lnu(C) in chicken-associated Campylobacter warrant attention due to antimicrobial selection pressure.