Epidemiological study of Campylobacter contamination of broiler farms in Belgium by amplified fragment length polymorphism analysis

Amplified fragment length polymorphism (AFLP) analysis was used for genetic typing of 88 Campylobacter jejuni subsp. jejuni and 4 Campylobacter coli isolates. Restriction endonucleases HindIII and HhaI were used in combination with the selective PCR primers HindIII+A and HhaIII+A. Selectively amplified PCR products were separated in an ABI 310 genetic analyser. After normalization, pattern similarity was calculated using the Pearson correlation coefficient. Banding patterns exhibiting 89.6 to 92.8% homology were obtained upon assessing the reproducibility of the method. As a consequence, a cut-off similarity value of 90% was used as the cut-off level for identical patterns. A total of 18 broiler flocks, including 16 independent and 2 successive flocks in the same broiler house, were sampled for Campylobacter. A wide range of samples was taken including caecal droppings, nipple water, footwear, animal (e.g. faecal material domestic/wild animals) and non-animal (e.g. compost heap, ditch water, puddle) material in the environment. The infection of the broiler flocks increased during rearing, with a total of seven positive flocks at the end of rearing. Almost exclusively C. jejuni subsp. jejuni was detected during rearing, with the exception of one flock with a mixed C. jejuni subsp. jejuni – C. coli infection. On the farms with Campylobacter-positive status, isolation was done most frequently in the environment from the puddles (3 out of 4 flocks), the faecal material from other poultry houses (2 out of 2 flocks), the ditch water (1 out of 1 flock) and dirty footwear used outside the broiler house (1 out of 2 flocks). Isolates that clustered together always originated from the same farm; while within a single farm only limited diversity (1-4 AFLP types) was found. Isolation of the same AFLP type from animals and environmental sources gave evidence for dispersal and circulation of Campylobacter in the environment. The clustering obtained by AFLP analysis was in very good agreement with the grouping of the isolates based on previously generated pulsed field gel electrophoresis fingerprints. We concluded that AFLP analysis is an attractive tool which can be used for typing large numbers of Campylobacter strains and is extremely useful for epidemiological investigations.