Validation of simple method for rapid detection of listeria monocytogenes in raw milk and kariesh cheese

ABSTRACT

Sixty raw milk and Karish cheese samples [30 of each] collected from dairy shops and street vendors were analyzed for presence of Listeria monocytogenes and other Listeria species using both conventional method and another simple method for rapid detection of the organism. Listeria monocytogenes was found in 3 [10%] and 5 [16.6%] of the examined raw milk and Karish cheese samples, respectively. The method used in the study proved high consistency with the conventional one. Isolates revealed from positive samples were identified biochemically using both conventional method and Minitek system. Listeria murrayi L. ivanovi and L. grayi were isolated in percentages ranged between 25 and 37.5 of 8 isolates revealed from raw milk samples, while of 14 isolates obtained from karish cheese samples, Listeria grayi L. murrayi and L. seeligeri were identified in percentages of 50, 28.5 and 21.4, respectively. Sources, conditions associated with this pathogen and how to control its incidence in dairy products were discussed, in addition to validation of the used method: