Molecular Epidemiology of Campylobacter coli isolated from Conventional and Antimicrobial-free (ABF) Swine and their Environment

Introduction:   Campylobacter is one of the leading pathogens causing foodborne illnesses in the US. Epidemiological evidence has indicated that food animals, including pigs, act as reservoirs of Campylobacterstrains that can infect humans.

Purpose: To determine the clonality or diversity of Campylobacter coli isolated from the conventional and antimicrobial free (ABF) production systems at farm, slaughter and environment using multilocus sequence typing (MLST).

Methods:   A total of 129 C. coli isolates were selected from fecal, environmental and carcass samples of ABF (N = 71) and conventional (N = 58) production systems. Seven housekeeping genes (asp, gln, glt, gly, pgm, tkt, unc) were amplified using PCR and the amplified product was sequenced. Sequence data was analyzed for the determination of allelic profiles and identification of sequence types (STs). Dendrograms and minimum spanning trees were generated to establish the relationships between the genotyped isolates.

Results: We identified 20 and 13 unique STs in the conventional and ABF production systems, respectively.  Isolates with similar sequence types were found between the pigs and their environment at farm and slaughter (ABF: 13, I_A = 0.1308; Conventional: 20, I_A = 0.1357). Higher genotypic diversity was observed among isolates from the conventional swine production systems (ABF: 0.3455 +/- 0.0901; Conventional: 0.3929 +/- 0.0805).  Phylogenetic analysis using the unique STs from the two production systems revealed a genotypically diverse population with the presence of C. coliisolates sharing a common ancestry. 

Significance: MLST Genotyping of C. coli isolates from two distinct production systems unveil a weak clonal population and diverse genetic makeup of this species.