Development of USDA-FSIS method for isolation of Listeria monocytogenes from raw meat and poultry.

A method was developed specifically to detect naturally occurring Listeria monocytogenes in meat because the traditional cold enrichment procedure was extremely slow and other procedures were ineffective. This method could identify beta-hemolytic Listeria colonies in 3-4 days. The use of a 2-stage enrichment, highly selective LPM agar, and a thin-layer horse blood agar plate for the detection of beta-hemolytic Listeria isolates are the important steps of this method. L. monocytogenes was recovered from 20 of 41 samples of frozen ground beef, 12 of 23 samples of pork sausage, and 7 of 22 samples of poultry. These results indicate that L. monocytogenes is common in raw meat and that this method is effective for its recovery.