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ABSTRACT

The genus Listeria is composed of six species, of which L. monocytogenes and L. ivanovii are pathogenic. Phosphatidylinositol-specific phospholipase C (PI-PLC) activity is a potential virulence factor, exhibited only by pathogenic Listeria spp. In the present investigation, 51 Listeria isolates were simultaneously tested for their PI-PLC activity by the PI-PLC assay as well as plating them on ALOA, a chromogenic selective medium. The study revealed that ALOA is economical and not only differentiated listeriae from non-listeriae but also the pathogenic Listeria spp. from non-pathogenic ones within 48 h. But its efficacy is less as compared to PI-PLC assay which detects the enzyme activity in mere 10-12 h. Thus, although ALOA has proved to be a selective and differential medium, PI-PLC assay certainly provides a more rapid and timely diagnosis.

Keywords: ALOA, L. monocytogenes, L. ivanovii, PI-PLC