Phenotypic heterogeneity of Campylobacter coli isolated from conventional and antimicrobial free swine at farm and slaughter

Thakur, Siddhartha
Zewde, B.
Gebreyes, Wondwossen
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The aim of this study was to determine the phenotypic and genotypic diversity of multiple Campylobacter coli isolates (n = 3) present in the same pig fecal and carcass samples at fann and slaughter, respectively. We isolated 1459 C. coli (1110 on farm and 349 from slaughter) from 908 pigs and 757 carcasses and characterized them for their antimicrobial susceptibility profile to a panel of six antimicrobials using the agar dilution method. A subset of 40 isolates representing 10 pigs and eight carcass samples were further genotyped by multi-locus sequence typing (MLST). Phenotypic diversity of C. coli isolates at the four fold minimum inhibitory concentration (MIC) levels within the same sample was detected in 39% (n = 192) pigs and 40.2% (n = 58) carcass swabs with no significant difference between the two sources (P = 0.721). Phenotypic heterogeneity based on the resistance patterns was observed in 32.5% (n = 162) of the farm samples and in 30.5% (n = 44) carcass swabs at slaughter (P = 0.64). Genotypic diversity based on MLST was detected in the 40 isolates which were represented by 22 sequence types (ST). In conclusion, we detected multiple C. coli subtypes from individual pig or carcass samples. Our study clearly signifies the importance of testing multiple colonies to make appropriate and valid conclusions in epidemiological based studies.