Differences in the Fecal Concentrations and Genetic Diversities of Campylobacter jejuni Populations among Individual Cows in Two Dairy Herds

Dairy cows have been identified as common carriers ofCampylobacter jejuni , which causes many of the human gastroenteritis cases reported worldwide. To design on-farm management practices that control the human infection sourced from dairy cows, the first step is to acquire an understanding of the excretion patterns of the cow reservoir. We monitored the same 35 cows from two dairy farms forC. jejuni excretion fortnightly for up to 12 months. The objective was to examine the concentration ofC. jejuni and assess the genetic relationship of theC. jejuni populations excreted by individual cows. Significant differences (P < 0.01) inC. jejuni fecal concentration were observed among the 35 cows, with median concentrations that varied by up to 3.6 log10 · g−1 feces. A total of 36 different genotypes were identified from the 514 positive samples by using enterobacterial repetitive intergenic consensus (ERIC)-PCR. Although 22 of these genotypes were excreted by more than one cow, the analysis of frequencies and distribution of the genotypes by model-based statistics revealed a high degree of individuality in theC. jejuni population in each cow. The observed variation in the frequency of excretion of a genotype among cows and the analysis by multilocus sequence typing (MLST) of these genotypes suggest that excretion ofC. jejuni in high numbers is due to a successful adaptation of a particular genotype to a particular cow's gut environment, but that animal-related factors render some individual cows resistant to colonization by particular genotypes. The reasons for differences inC. jejuni colonization of animals warrant further investigation.