Monika Moravkova^1,, Veronika Verbikova¹, Veronika Michna¹, Vladimir Babak¹, Hana Cahlikova², Renata Karpiskova², Petr Kralik¹

In this study, a total of 175 samples of ready-to-eat vegetables, frozen vegetables and sprouted seeds originating in 10 states of the European Union and from 32 manufacturers were collected during a period of one year and examined for the presence of Listeria monocytogenes using standard culture methods and qPCR. In addition to these methods, isolation of Listeria monocytogenes was also carried out following a unified sample preparation for combined downstream use in culture and qPCR analysis. Standard culture and culture preceded by unified sample preparation, showed that L. monocytogenes was present in 6.9% and 11.4% of analyzed samples, respectively, in low numbers. Application of qPCR revealed only 2.3% of samples to be positive for L. monocytogenes in small quantities (less than 10 cells/gram). A statistically significant higher occurrence of L. monocytogenes was seen in frozen vegetables compared to ready to eat vegetables (p<0.01; Fisher’s exact post-hoc tests with Bonferroni’s correction) or sprouts (p<0.05; Fisher’s exact post-hoc tests with Bonferroni’s correction). Therefore, temperature abuse in food containing pieces of frozen vegetables without any processing such as cooking, may pose health risks, especially for sensitive individuals such as pregnant women, children, the elderly, and immunocompromised individuals.

Listeria monocytogenes, Foodborne pathogens, Molecular methods, qPCR, Ready-to-eat