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An improved method was developed for the rapid isolation and identification of Salmonella in chicken carcasses. Considering the heavy presence of Proteus mirabilis in the poultry-production environment, we investigated combinations of selective bacterial growth media that promote the growth of Salmonella but inhibit that of P. mirabilis. The improved method was evaluated using standard methods described in the Bacteriological Analytical Manual (BAM) by the U.S. Food and Drug Administration (FDA), and the Microbiology Laboratory Guidebook published by the U.S. Department of Agriculture Food Safety Inspection Service (USDA/FSIS). A total of 44 chicken carcasses were analyzed for Salmonella using the three methods. The FDA/BAM method showed a poor sensitivity and specificity, especially when the tetrathionate (TT) broth was applied. The improved method offered an excellent specificity (>95%) and shortened the time of isolation and identification from 4 to 5 days to less than 3 days, consequently reducing the costs.

The capability of an assay to detect Listeria monocytogenes from artificially inoculated fresh-cut produce such as cantaloupe and mixed salad was demonstrated. An oligonucleotide probe that becomes fluorescent upon hybridization to the target DNA (Molecular Beacon, MB) was used in a real-time polymerase chain reaction (PCR) assay. As few as 4 to 7 colony-forming units (CFU) of L. monocytogenes per 25 g of artificially contaminated produce could be detected. A comparison of 2 commercially available kits using MB-PCR (iQ-Check, Bio-Rad Laboratories) and conventional PCR (BAX, Dupont Qualicon) was performed on artificially inoculated produce. The time required to detect L. monocytogenes (from produce to PCR) was considerably shorter for the iQ-Check protocol (approximately 26 h) compared with the BAX-PCR (approximately 52 h). The iQ-Check protocol was also used to confirm the identity of the L. monocytogenes isolates obtained during a microbiological screen of conventional and organic leaf lettuce and alfalfa sprout samples from local supermarkets. The iQ check protocol was successful in differentiating L. monocytogenes isolates from other Listeria spp. such as L. welshimeri, L. innocua, and L. ivanovii. This is the 1st report of the application of the MB probe being used for real-time detection of L. monocytogenes in whole and fresh-cut produce.

An important component of a Hazard Analysis Critical Control Point (HACCP) approach applied to animal production is reducing the carriage of food-associated pathogens by animals. Two approaches that have both great potential for reducing pathogen colonization of animals and merit for practical application include (1) vaccination and (2) competitive exclusion. Vaccination involves acquisition of immunity in an animal following exposure to an attenuated pathogen or an antigen of a virulent microorganism. Adherence factors that influence bacterial colonization of animals are useful antigens for vaccines. A strategy to developing a vaccine to reduce carriage of pathogens includes (1) identifying sites of colonization by the pathogen in the animal, (2) defining the mechanism of colonization, (3) characterizing genes that encode colonization factors, (4) transforming the colonization factor antigen genes into a suitable nonpathogenic vector, and (5) determining the optimal methods of immunization. Studies are underway to identify colonization factors of Escherichia coli O157:H7 for use in vaccine development to protect cattle from colonization by this pathogen. Competitive exclusion involves the use of microbial cultures that out-compete pathogens from colonizing specific niches. A science-based approach to identifying/developing useful competitive exclusion cultures is to: (1) define how a pathogen colonizes the site of interest, (2) isolate microbes that colonize the same site and produce metabolites that inhibit or kill the pathogen, and (3) verify that the inhibitory microbes, when introduced into pathogen-free animals, can reduce or prevent colonization by the pathogen. This approach has been used successfully to identify defined bacterial cultures that can greatly reduce colonization of Campylobacter jejuni in poultry. Commercial implementation of techniques of these types is an essential part of the overall HACCP approach to reducing the prevalence of foodborne pathogens from farm to fork.

A spore pool inoculum (I) of 4 each type B and E nonproteolytic C. botulinum was applied at levels of log10-2 to 4 spores per 2–3g sample of cooked turkey (0, 1.47, and 2.2% brine (B), respectively), stored under vacuum at 4, 8, 12, 16, 20, and 30°C up to 180 days. Earliest toxin production at the above temperatures (T) was detected in 0% brine meat after > 180, 8, 4, 1.5, 1.5, and 0.5 days, in the 1.47% brine after 70, 8, 7, 2, 1.5 and 1 days, and in the 2.2% brine after 130, 10, 9, 2.5, 1.5 and 1 days, respectively. Lag phase (LP) was affected significantly by T, I, and Txl (p