DNA identification and characterization of Campylobacter jejuni and Campylobacter coli isolated from caecal samples of chickens in Grenada

Abstract

To speciate Campylobacter strains from the caeca of chickens in Grenada using PCR and to evaluate DNA-based typing methods for the characterization of these isolates. Isolates were speciated with two multiplex PCR assays and were typed with flaA-RFLP, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Results confirmed that Campylobacter coli strains were more predominant than Campylobacter jejuni strains. From 56 isolates, 18 were misidentified using biochemical tests. PFGE typing gave the highest discriminatory power among the methods used (Simpson's index of diversity, D=0.9061). However, the combination of flaA-RFLP, PFGE and MLST results gave the highest discrimination for subtyping of these isolates (D=0.9857). A band position tolerance of 4% in BioNumerics was the most appropriate for the analysis of this database. MLST profiles were generally concordant with PFGE and/or flaA-RFLP types. Several isolates exhibited new MLST sequence types (STs), and 43 of the 49 Camp. coli strains belonged to the ST-828 clonal complex. Campylobacter coli was the most prevalent species isolated from broilers and layers in Grenada, and a combination of restriction and sequence methods was most appropriate for the typing of Camp. coli isolates. Campylobacter coli STs clustered with described poultry-associated Camp. coli STs by phylogenetic analysis. Further studies to understand the predominance of Camp. coli within Campylobacter spp. from chickens in Grenada may help elucidate the epidemiology of these pathogens in chickens.