Comparison of Four Procedures to Detect Listeria spp. in Foods.

A comparison was made of four procedures to detect Listeria spp. in two food categories. The study comprised 309 assays, 71 on milk from both infected and uninfected cows, and 238 on ten types of fresh vegetables. A sample was considered positive if it could be detected by at least a single method and if isolates could be confirmed as Listeria spp. The procedures detected 98-100% of the positive milk samples. Recovery from vegetable samples ranged from 45 to 86%, probably because of low levels of Listeria spp. in the presence of mixed flora. The ELISA procedure of the Organon Teknika® corporation detected 68% of the 44 positive vegetable samples; the GENE-TRAK®DNA probe, 45%; the U.S. Food and Drug Administration (FDA) culture procedure, 75%; and the FDA probe procedure, 86%. Recovery was higher with LiCl-phenylethanol-moxalactam agar (FDA probe procedure) than with modified McBride Agar (FDA culture procedure).

Salmonella Surveillance by the Food and Drug Administration: A Review 1974-1985.

Since 1974, the Food and Drug Administration's (FDA's) Minneapolis Center for Microbiological Investigations has been responsible for confirmation and serotyping of Salmonella cultures originally isolated by FDA field laboratories. The data have subsequently been entered into FDA's Microbial Information System for storage and analysis. A summary of the data accumulated from 1974 to 1985 is provided as an overview of FDA's Salmonella surveillance activities for the period.