INCIDENCE OF LISTERIA-MONOCYTOGENES IN PACKAGES OF RETAIL FRANKS

Twenty brands of retail frankfurters obtained from local supermarkets were examined for the presence of Listeria spp, Listeria spp. were fou nd in 8 of 20 brands and Listeria mono-cytogenes in 6 of the 20 brands tested. In retail samples from 19 brands of frankfurters, Listeria sp p. were found at an overall incidence of 10% (9 of 93 packages) of whi ch 7.5% (7 of 93) contained L. monocytogenes and 2.5% (2 of 93) Lister ia innocua. However, another brand (No. 20) had incidence levels as hi gh as 71% (17 of 24) for L. monocytogenes and 81% for all Listeria spp . Testing the internal meats versus liquid exudates demonstrated that Listeria spp. were found only in the exudate, indicating that the pres ence of Listeria was likely due to postprocess contamination. Most pro bable number (MPN) analysis indicated that L. monocytogenes was presen t at levels of 0.34 to 2.3 MPN per ml of exudate, or 4.3 to 27.6 MPN p er package. Chemical and microbial analyses found brand No. 20 to have the highest pH and NaCl levels among five brands tested; this combina tion may favor Listeria spp. and suppress competing microorganisms. A prior outbreak of listeriosis from the consumption of nonreheated fran ks, together with the data presented herein, indicates there is a pote ntial foodborne hazard in consuming uncooked franks or in cross-contam ination of other foods from handling package exudate.