Methods for Selective Enrichment of Campylobacter spp. from Poultry for Use in Conjunction with DNA Hybridization

A DNA hybridization test was investigated for application to the detection of Campylobacter spp. in poultry samples. The test chemistry involves solution phase hybridization and detection by means of an enzymatically generated colorimetric endpoint. DNA probes used in the test system are targeted to unique sequences of ribosomal RNA and are specific for Campylobacter jejuni , Campylobacter coli , Campylobacter lari , and Campylobacter fetus subsp. fetus . Initial experiments with pure cultures of C. jejuni established the sensitivity limit of the DNA hybridization assay at approximately 10^6-7 CFU per sample. Experiments were designed to define optimal conditions for recovery and selective enrichment of Campylobacter spp. from chicken carcasses for use in conjunction with the DNA hybridization assay. Following overnight enrichment, cultures were swabbed onto Campy-Cefex agar plates and allowed to incubate for 24 h. This overnight growth was then suspended and assayed with the DNA probe. The remainder of the overnight enrichment was centrifuged and the resulting pellet was analyzed. Thirty-eight chicken carcasses were assayed for Campylobacter spp. by DNA probe and culture methodology employing culture enrichment and selective plating. Culture procedures isolated Campylobacter spp. from 23 carcasses, while the DNA probe assay detected the organism from 21 carcasses. The DNA probe registered five "false" positives and seven "false" negatives relative to the cultural bacteriologic approach.