[Listeria monocytogenes and Listeria sp in heat-processed products]

Presence of Listeria monocytogenes in thermoprocessed food which is vacuum packaged, refrigerated stored and eaten uncooked or minimally heated was investigated. Thirty samples including sausage, large sausage with ham, spring large sausage, liverwurst and bologna were examined. Listeria monocytogenes was isolated and identified according to USDA-FSIS method for meat products, simultaneously with McBride agar. Seven out of 30 samples were found to contain listeriae. Five isolates were identified as Listeria monocytogenes through Gram coloration, culture appearance, biochemical test and serotyping. This product results potentially risky for the susceptible population. The presence of this microorganism in this kind of product suggests environmental post-process contamination or insufficient thermal process.