Prevalence and Distribution of Campylobacter jejuni and Campylobacter coli in Retail Meats

Nine cooperating laboratories, distributed throughout the United States, determined the interlaboratory reproducibility of a sensitive, selective method for isolation of Campylobacter jejuni and Campylobacter coli from foods, and determined the prevalence and distribution of the organism in retail meats. A double-blind inoculated/recovery experiment demonstrated the ability to detect two cells of C. jejuni and C. coli per g of meat at a rate of 96% among the cooperating laboratories. However, a 7.5% false-positive rate for the presumptive detection of the organism was also reported. Samples of ground beef, beef flank steak, lamb stew meat, broiler chicken, pork sausage (without antimicrobials), and pork chops were selected to assess the presence of campylobacters. Each cooperator purchased five of each of the above samples from the refrigerated case of two retail outlets at quarterly intervals throughout the year. A total of 2,160 retail samples were analyzed for the presence of C. jejuni and C. coli . Results indicated that about 30% of the 360 chickens sampled yielded the organism. Analysis of 1,800 red meat products yielded campylobacters at a rate of about 5.1%. Pork samples yielded C. coli and other meats yielded C. jejuni . Higher numbers of isolations from the red meats were made during June and September (8.6%) as compared with December and March (4.2%). These results provide a baseline, for the prevalence of campylobacters in these selected foods, and also support epidemiologic data associating mishandled foods of animal origin as a potential vehicle in human gastroenteritis.

Recovery of Salmonella Species from Nonfat Dry Milk Rehydrated Under Rapid and Reduced Pre-enrichment Conditions: Collaborative Study

A collaborative study was conducted to compare the relative efficiency of the AOAC rapid rehydration method with the reduced rehydration soak method for the recovery of Salmonella species from nonfat dry milk (NFDM). In the AOAC method, a 25 g sample of NFDM is rapidly rehydrated at a 1:9 sample/water ratio and mixed by swirling. After 60 min, the flask contents are adjusted to a pH of 6.8, and 0.45 mL of 1% aqueous brilliant green dye solution is added. The flasks are then incubated at 35°C. In the soak method, a 25 g sample of NFDM is gently added to the sterile brilliant green (BG) water at a 1:9 sample/ BG water ratio and allowed to soak undisturbed for 60 min at room temperature before incubation. Twelve collaborators analyzed 3 shipments of samples with the following results for the AOAC and soak methods: shipment 1—31 and 46 positive samples, respectively, with a 48% increase in detection by the soak method; shipment 3-45 and 66 positive samples, respectively, with a 47% increase in detection by the soak method; shipment 2—no significant difference in recovery of Salmonella species by the 2 methods. It is recommended that the official final action method for the detection of Salmonella species, 46.054- 46.067, be revised to use the soak method for the analysis of nonfat dry milk.

Timed-Release Capsule Method for the Detection of Salmonellae in Foods and Feeds

A new method was developed for the detection of injured and uninjured salmonellae in foods and feeds. The steps of pre-enrichment in a nonselective broth and selective enrichment in a selective medium were combined into a single procedure. This was achieved by the gradual release of selective agents from wax-coated gelatin capsules added at the time of inoculation of nonselective basal broths. Pre-enrichment in lactose broth was combined with selective enrichment in tetrathionate or selenite-cystine broth by using timed-release capsules containing iodine or selenite. Five different categories of foods and feeds, naturally contaminated with salmonellae, were examined to compare the efficiencies of the capsule methods with conventional procedures. Combination of the separate steps of pre-enrichment and selective enrichment into a single procedure was feasible and resulted in substantial savings of labor and materials.