Retail foods may be an important vehicle for community-wide dissemination of antimicrobial-resistant E. coli and ExPEC, which may represent a newly recognized group of medically significant foodborne pathogens.

Field laboratories of the U.S. Food and Drug Administration collected and tested 11,312 import and 768 domestic seafood samples over a 9-year period (1990 to 1998) for the presence of Salmonella. The overall incidence of Salmonella was 7.2% for import and 1.3% for domestic seafood. Nearly 10% of import and 2.8% of domestic raw seafood were positive for Salmonella. The overall incidence of Salmonella in ready-to-eat seafood and shellfish eaten raw was 0.47% for domestic--one shucked oyster and one shark cartilage powder. The incidence in the 2,734 ready-to-eat import seafood was 2.6%--cooked shrimp, shellfish or fish paste, smoked fish, salted/dried fish, and caviar. The incidence in import shellfish consumed raw was 1% in oyster, 3.4% in clams, and 0% in mussels. The incidence in raw, import fish was 12.2%. Distribution of Salmonella in seafood on a regional basis indicated the incidence to be highest in central Pacific and Africa and lowest in Europe/Russia and North America (12% versus 1.6%). Data on a country basis indicated Vietnam to have the highest (30%) and Republic of Korea the lowest (0.7%). While the most frequent serotypes in import seafood were Salmonella Weltevreden (1st), Salmonella Senftenberg (2nd), Salmonella Lexington, and Salmonella Paratyphi-B (3rd, equal numbers for each serotype), the top 20 list included Salmonella enteritidis (5th), Salmonella Newport (6th), Salmonella Thompson (7th), Salmonella typhimurium (12th), and Salmonella anatum (13th), commonly involved in foodborne illness in the United States. Because the incidence in the present study is based on only a small fraction of the seafood imported into the United States, efforts should be directed toward implementation of hazard analysis and critical control points to reduce the incidence of Salmonella in seafood without relying on testing for Salmonella.

Summary -Camembert cheeses were made at 3 different times with milk containing initially 10', 103 or 105 Listeria monocytogeneslml.A nisin-producing starter composed of a pair of isogenic protease positive and protease negative strains of Lactococcus lactis subsp lactis was used to inhibitNisin concentration in curd and in cheese paralleled the growth of lactococci. Maximum nisin concentration of ca 700 IU/g was obtained in curd at 9 h, then nisin concentrations decreased slowly during 9-24 h and dramatically during ripening. In the presence of nisin, the numbers of L monocytogenes decreased rapidly from 6 h to 24 h. This inhibitory effect continued until the end of the second week of ripening in the core of Camembert cheeses, leading to a reduction of 3.3 log Listerialg (average from 3 experiments) compared to the initial level in cheese milk. Thereafter, regrowth occurred in Camembert cheeses, sooner on the surface than in the interior. However, a difference of 2.4 log CFU/g between numbers of Listeria in cheese made with Nis+ and Nis-starter cultures was maintained throughout ripening (6 weeks). Nisin was particularly effective when milk contained 10 1 or 10 3 L monocytogeneslml.

To assess the food supply as a possible vehicle for antimicrobial-resistant and extraintestinal pathogenic Escherichia coli (ExPEC), we defined the prevalence, density, clonal diversity, virulence characteristics, and antimicrobial resistance profiles of E. coli among diverse retail food items. A microbiological survey was undertaken of 346 food items (vegetables, produce, beef, pork, chicken, and turkey) purchased as a convenience sample from 16 retail markets within the Minneapolis-St. Paul area in 1999-2000, with selective cultures for E. coli and extensive molecular and phenotypic characterization of E. coli isolates. Meats, particularly turkey products, were often extensively contaminated with antimicrobial-resistant E. coli and ExPEC, to a much greater extent than were produce items, even those from farmer's markets. Moreover, meat-source E. coli differed substantially from produce-source E. coli with respect to phylogenetic background (more commonly from virulence-associated phylogenetic groups B2 or D), virulence genotype (more extensive), and antimicrobial resistance profile (more extensive). Molecular typing methods matched four turkey-source isolates to selected human clinical and fecal isolates representing the O7:K1:H-, O83:K1, and O73/O77:K52:H18 ("clonal group A") clonal groups of ExPEC. Meats purchased in grocery stores, particularly turkey products, are frequently contaminated with antimicrobial-resistant E. coli and ExPEC. Further study is needed regarding the origins and health consequences of these foodborne organisms, both to clarify the need for and to guide the possible development of appropriate regulatory and monitoring systems and preventive interventions.