Study of aerotolerant Campylobacter Jejuni in broiler production process

Abstract

Campylobacter jejuni is the leading cause of human gastroenteritis worldwide. Although they are microaerophile and sensitive to oxygen, aerotolerant C. jejuni has been reported in many countries. Currently, limited information on aerotolerant C. jejuni in Thailand has been reported. Therefore, the objectives of this study were 1) to examine the occurrence of aerotolerant C. jejuni in farms, slaughterhouses and retail markets and compare the level of aerotolerant strain between different sample types at the farm (i.e., cloacal swabs VS manures) and slaughterhouse level (i.e., cecal contents VS carcass rinses) and 2) to identify common genotypes of aerotolerant and aerosensitive C. jejuni strains in each poultry production stage. A total of 275 C. jejuni strains isolated from cloacal swabs, manures, cecal contents, carcass rinses and raw chicken products were tested for aerotolerance by aerobic shaking at 150 rpm under aerobic condition at 42°C for 24 hours. Representatives of C. jejuni isolates were primarily genotyped by flaA SVR sequencing technique and further subtyped by MLST. The highest number of aerotolerant C. jejuni isolates were found at the slaughterhouse stage (56.0%), followed by the retail market stage (51.0%) and the farm stage (41.3%). The level of aerotolerant C. jejuni strain between different sample types at the farm and slaughterhouse level were not significantly different. Hyper-aerotolerant strain was not detected in this study as no bacterial strains survived 24 h of aerobic shaking. The longest viability of C. jejuni strains under aerobic culture was 18 h with the viable counts of 2.59 log CFU/ml, 3.53 log CFU/ml and 3.06 log CFU/ml at the farms, slaughterhouses and retail markets, respectively. Forty-one flaA SVR allele types and 17 sequence types (STs) were identified among aerotolerant and aerosensitive C. jejuni strains. The predominant allele types in aerosensitive and aerotolerant strains was flaA SVR allele number 142 and 783, respectively. Mostly, genetic similarity was found in isolates from farms and slaughterhouses. For MLST, the results revealed that the most frequently detected ST in aerosensitive strains was ST-460, while ST-1232 was predominant in aerotolerant strains. The main clonal complexes (CCs) observed in this study were CC- 353, followed by CC-45. Most of the STs (e.g., ST-1075 and 1232) found in this study were previously identified in chickens and gastroenteritis patients in Thailand, which highlight the significance of broilers as one of the most important sources of human campylobacteriosis. Our findings suggested that the reduction of Campylobacter contamination in the final products by implementation of good hygienic practices and strict biosecurity in poultry production steps is essential and would help decrease the transmission of Campylobacter to human, which eventually reduce the number of foodborne campylobacteriosis cases.