The design of real-time polymerase chain reaction (PCR) assays for the detection of meat in processed products has focused on using small amplicons, often to the detriment of specificity. However, the relationship between amplification rates and the amplicon size for processed meat products has yet to be determined. To investigate this relationship, real-time PCR assays were designed to give a series of amplicons of increasing size. These assays were then used to assess amplification rates, in relation to amplicon size, in processed meat matrices. Although the most sensitive assays were those that used the smallest amplicons, amplification was still observed using amplicons of 351 base pairs for highly processed samples. It was found, therefore, that although in general, amplicons should be as small as possible, larger amplicons give efficient amplification and that small amplicons should not be chosen if they compromise assay specificity.

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.