Poster presentation at |CA|MA|2013| (Trani, Italy, 3-7 June 2013)
Prevalence of Listeria monocytogenes and E. coli O157:H7 in rocket (Eruca sativa), cucumber (Cucumis sativus) and strawberry (Fragaria ananassa) samples
Hadjilouka A., Madjourani K.-S., Koubou V., Paramithiotis S., Mataragas M., Drosinos E.H.
Laboratory of Food Quality Control and Hygiene, Department of Food Science and Technology, Agricultural University of Athens
The aim of the present study was to determine the prevalence of Listeria monocytogenes and Escherichia coli O157:H7 in ready to eat fresh products and specifically in rocket, cucumbers and strawberries. The detection of both pathogens was based on the respective ISO methods with a parallel study for the comparison of two chromogenic culure media: ALOA and RAPIDL.mono in the former case, CT-SMAC and Fluorocult in the latter. Moreover, culture-independent techniques (specific PCR, RT-qPCR) were applied in the enrichment broths in order to assess their efficacy in detecting the pathogens. Confirmation of the suspect colonies was performed by hemolysis, rhamnose and xylose fermentation as well as specific PCR for L. monocytogenes; Latex Test and specific PCR for E. coli O157:H7. Based on the results of biochemical tests and molecular analyses, prevalence of L. monocytogenes was 7% in rocket, 6% in cucumbers and 3,8 % in strawberries, while prevalence of E. coli O157: H7 was 7% in rocket, 3% in cucumbers and 3.8 % in strawberries. Furthermore it was concluded that parallel use of more than one chromogenic media is necessary for accurate estimation of L. monocytogenes and E. coli O157:H7 prevalence and that plating on chromogenic media with inhibitory agents against antagonistic microbiota cannot be reliably replaced by direct PCR or RT-qPCR in the enrichment broths.