THE OCCURRENCE AND INITIAL NUMBERS OF LISTERIA IN IRISH MEAT AND FISHPRODUCTS AND THE RECOVERY OF INJURED CELLS FROM FROZEN PRODUCTS

A total of 549 samples of meat, fish and poultry products purchased fr om retail outlets in the Dublin area were examined for the presence of Listeria spp., using a standard recovery method and a new resuscitati on method. Listeria spp. were most frequently isolated from frozen bee f burgers (97%) and fish fingers (95%). Cooked meats which were prepac kaged by the manufacturer were negative for Listeria spp. The pathogen was isolated from 21% of cooked meats which were sold retail unpackag ed indicating post-process contamination. Standard recovery methods ga ve Listeria counts of between 0.7 and log10 5.0 cfu/g on frozen produc ts. Using a resuscitation method, counts were up to log10 2.5 cfu/g hi gher, indicating the presence of large numbers of injured Listeria cel ls. The significance of the numbers of Listeria found in the various f oods as well as the recovery of injured cells with the new resuscitati on method is discussed.