Survival of a native toxigenic isolate of Listeria monocytogenes CFR 1302 during storage of milk-based foods can be a potential cause of health risk.

The ability of a native toxigenic culture of Listeria monocytogenes CFR 1302 to survive and elaborate
associated toxigenic trait in ice cream and mango pulp-based lactic fermented milk was studied. The culture
of L. monocytogenes inoculated at two initial levels of 4.6 and 5.6 log10 CFU/ml almost remained unaltered
during storage of the food products. However, in both the milk-based products, a marginal increase in viable
population was observed during 2–4 d of storage as against the initial inoculum levels. The toxigenic trait,
listeriolysin ‘‘O’’ was detected by PCR based on species-specific hlyA primers in the two products without any
step of enrichment. The positive amplification in PCR was evidenced with initial population levels of 6.3, 7.3,
and 8.3 log10 CFU/ml of the respective products. In culture broth, PCR detection was positive with the lowest
level of 2.3 log10 CFU/ml. The established pathogenic strain of L. monocytogenes Scott A used as a reference
culture revealed almost the same behavior to that of native culture in the food products. The findings of
present study bring into focus that, irrespective of low storage temperatures, there exists the potential health
hazard associated with foods initially contaminated with risk population levels of L. monocytogenes.