Assessment of the Accuprobe Listeria monocytogenes culture identification reagent kit for rapid colony confirmation and its application in various enrichment broths

Abstract

The Accuprobe Listeria monocytogenes Culture Identification Reagent Kit, a nonradioactive probe, was evaluated as a colony confirmation test and in different selective or nonselective enrichment broths. The probe was 100% sensitive and 100% specific when applied to isolated colonies. The minimal detection limit in physiological saline was established to be about 105 CFU of L. monocytogenes. Hybridization done directly in broths seeded with L. monocytogenes showed variable results. Three nonselective broths (Todd- Hewitt broth, brain heart infusion broth, and tryptic soy broth) and one selective broth (FDA) gave positive reactions at an inoculum of 5 x 106 CFU, whereas two other selective broths (UVM, and PALCAMY) gave negative reactions with up to 108 and 109 CFU. In FDA broth, the level of detection of L. monocytogenes was not modified by the presence of other organisms in mixed cultures.