LAUSR

ABSTRACT Poultry are the main source of Campylobacter infection worldwide. To obtain information on Campylobacter-infected flocks and create a reference for preventing and controlling Campylobacter at farm level, Campylobacter isolates were recovered from broilers and the environments of nine chicken flocks in two farms during growth. The genetic relationship between the Campylobacter isolates was determined using multilocus sequence typing. Flocks were colonized as early as 3 weeks after introduction to the farm. The highest colonization rate was more than 90% and occurred 4–6 weeks after introduction to the farm. Quantitative data showed that the highest Campylobacter loads appeared at 1–2 weeks after initial colonization. Campylobacter loads in cloacal swabs in four flocks were significantly higher at 5 weeks than at 3 weeks (P < 0.05). Multilocus sequence typing of 171 selected isolates revealed 20 sequence types (STs), which consisted of 12 STs for Campylobacter jejuni and eight for Campylobacter coli isolates. The STs of the Campylobacter isolates recovered from farm 1 were more diversified than those from farm 2. The STs of environmental samples were highly consistent with those of the cloacal swab samples. The consistency between Campylobacter STs in the environmental and cloacal swab samples suggested that the environment might be one of the main sources of infection. Thus, our study highlights the prevalence and contamination load of Campylobacter in broilers during their rearing period and emphasizes the need for control and prevention measures for Campylobacter infection in broilers, which is also important for human health.