Frecuencia de Listeria spp., en Quesos Colombianos Costeños

Objective. To determine the frequency of Listeria spp., in coastal fresh cheeses,distributed in popular market places of Montería and Cereté cities. Materials andmethods. Keeping in mind the economic importance of this cattle area for Colombia,217 samples were collected between June and August of 2005, the obtained isolationswere identified by presumptive biochemical tests, multiple-PCR-(L1-U1/LF-LR) andbiochemical tests for species confirmation. Additionally the frequency of gender specieswas determined and the antimicrobial resistance of more frequency strains wascharacterized. Results. Biochemical tests and PCR detected 49 positive isolations forListeria (22.58%), of which 16.33% (8/49) corresponded to Montería and 24.40% (41/168)to Cereté. Frequency for species was 14.75% for L. ivanovii, 2.30% for L. innocua,1.84% for L. welshimeri and 1.38% for L. seeligeri, L. monocytogenes was not detected.Only 3/32 stumps of L. ivanovvi (9.38%) showed resistance to penicillin, streptomycinand erythromycin respectively. Conclusions. The results confirm that the coastal cheesesare frequently contaminated with Listeria spp. The presence of L. ivanovii pathogeninvolved in some cases by opportunist infections in human and L. innocua microorganismused in many food industries as indicator of the grade or sanitization quality; demonstratesthat the production conditions and marketing are not good and that the consumption ofcoastal cheese is not safe. The antimicrobial resistance although lower shows possibilitiesfor the horizontal and/or vertical transmission of resistance genes.