Validation of an improved method for detection of Campylobacter jejuni in foods

Campylobacter jejuni ATCC 29428 and 33560 were inoculated separately into beef muscle, ground beef, and chicken skin to yield approximately 10 to 100 CFU/g of food sample. The samples were stored at 4 degrees C for 10 d. On days 0, 3, 7, and 10, enrichment cultures in Bolton broth supplemented with antibiotics, with and without blood supplementation were made for each sample, for 24 and 48 h following the Food and Agricultural Products Center (FAPC) and the Food and Drug Administration (FDA) protocols. Enumeration of the organisms in the enrichment cultures was done on Campylobacter Karmali selective agar after 24 and 48 h of enrichment to compare the extent of growth in both protocols. There were no significant differences between counts recovered using the FDA and the FAPC methods for detection of Campylobacter jejuni for either strain in any of the food products tested (P > 0.05). No significant differences were observed in performance of enrichment broth supplemented with and without blood (P > 0.05). After 48 h of enrichment, the counts recovered were similar for all products. The organisms were detectable on all days of storage in raw chicken skin, beef, and ground beef samples after both 24 and 48 h of enrichment. The results from the FAPC method for detection of C. jejuni from food were not different from the FDA method. While in the proposed method incubation at 37 degrees C was adequate for the strains tested it is recommended that both enrichment temperatures be used for naturally contaminated samples to ensure detection of all strains that might be present.