Isolation of listeria monocytogenes from smoked cheese

Samples of smoked, salted cheese were collected from local markets of the city of Taiz. They were tested for the presence of Listeria monocytogenes . Data revealed that the pathogen was only recovered from 12.5% of cheese samples anayzed under this study. Other listeria] species were not isolated from cheese, directly plated onto selective agar media. Direct plating gave very ]ow counts (20 CFU/g or less) of L. monocytogenes, naturally contaminated smoked cheese. Selective enrichment of samples at 370C for 48 hr was necessary for isolating Listeria spp., present in cheese along with other co-contaminating microflora. The natural microflora of smoked cheese, especially Enterococci and Staphyocoeci, grew or developed diagnostic traits similar to those of L. monocytogenes in Listerial selective agar (Oxoid) . When increased volumes (>0.2ml) of samples were spread, Alzoreky- Sandine Listeria Medium (ASLM) recovered contaminated listeriae while inhibiting indigenous microorganisms of cheese. Results of this investigation emphasize the need to adopt a standard procedure for manufacturing smoked cheese in Yemen