Survey of the incidence of Listeria monocytogenes and other Listeria spp. in experimentally irradiated and in matched unirradiated raw chickens.

Listeria spp. were sought in 32 chickens experimentally irradiated (2.5 kGy) and in 25 matched unirradiated chickens. Using the modified Food and Drug Administration method only three of the chickens were positive for L. monocytogenes. Using the more sensitive cold enrichment method 30 were found positive. The proportion of carcasses contaminated with L. monocytogenes was lower in the irradiated birds than in the unirradiated birds. The results also indicated that the numbers of L. monocytogenes in the irradiated birds were lower than in the unirradiated birds. The only other species of Listeria isolated was L. innocua, which was found on 44% of unirradiated chickens, but on none of the irradiated chickens.