GENETIC RELATEDNESS AND RISK FACTORS ASSOCIATED WITH CAMPYLOBACTER IN THAI BROILER PRODUCTION CHAIN

Abstract

Campylobacter is considered as the major foodborne bacterial pathogen worldwide. Consumption and handling of contaminated food, particularly poultry meat product, are the important cause of Campylobacter infection. To reduce the number of human cases, the epidemiology of Campylobacter in poultry must be better understood. In Thailand, only limited information on Campylobacter in chicken meat production has been reported. Therefore, the objectives of this study were 1) to determine the prevalence and risk factors associated with Campylobacter in Thai broiler flocks and 2) to investigate genetic relatedness of Campylobacter strains isolated from broiler production chain in Thailand. Campylobacter colonization status was identified in 250 broiler flocks which were mainly raised in central and eastern parts of Thailand. Moreover, farm and flock data was collected by structured questionnaires. To identify risk factors associated with Campylobacter colonization in broiler flocks, logistic regression model (LRM) and generalized estimating equations (GEE) were performed. The distribution and genetic relatedness of Campylobacter were determined in 5 broiler production chains. flaA SVR sequencing and multilocus sequence typing (MLST) were used as genotyping methods in this study. Of 250 examined broiler flocks, 119 flocks were tested positive for Campylobacter (47.60%; 95% CI 41.41 - 53.79%). Most positive flocks had high level of within-flock prevalence (>75%). C. jejuni was the predominant species observed in this study, followed by C. coli. For the risk factor analysis, the history of Campylobacter colonization in previous flocks was identified as the most important risk factor associated with Campylobacter colonization in examined broiler flocks. Amongst 311 Campylobacter isolates from breeders to slaughterhouses selected for genetic characterization, 29 flaA SVR alleles and 17 sequence types (STs) were identified. The common clonal complexes (CCs) found in this study were CC-45, CC-353, CC-354 and CC-574. Mostly, C. jejuni isolated from breeders were distantly related to those isolated from broilers and chicken carcasses, while C. jejuni isolates from the slaughterhouse environment and meat products were similar to those isolated from broilers. Our findings underline the importance of hygienic practices on farm and slaughterhouse as well as strict biosecurity as the effective tool for reducing the transmission of Campylobacter from chickens to humans.