Methods of analyzing foods for purposes of identifying L. monocytogenes are complex and timeconsuming.
The present FDA method, revised in January 2003, uses a single enrichment broth,
buffered Listeria enrichment broth, and requires 24 to 48 hours of enrichment, followed by a
variety of agars and, finally, biochemical confirmation. Total time to identification is from 5 to 7
days. Many other enrichment broths, such as UVM broth and Fraser broth, are also included in
various protocols. Agars that have been extensively evaluated include Oxford agar, PALCAM,
LPM plus esculin and ferric iron and MOX.
New molecular biology techniques have been used to develop various rapid-screening kits for
L. monocytogenes. These kits generally rely on ELISA, PCR, and probe-based identification.