Molecular characterization of Listeria monocytogenes isolated from foods

ABSTRACT

A total of 30 strains of "Listeria monocytogenes" isolated from different foods (16 of different kinds of sausage, 14 cheese) purchased at groceries of São Paulo City were ribotyped and analysed for the presence and expression of hemolysin gene and production of phosphatidylinositol-specific phospholipase C-PI-PLC enzyme. The "L. monocytogenes" strains were differentiated into six ribotype classes. A total of 13 (43.3(per cent)) from these strains belong to the same ribotype (ribotype I), and was coincident to the ribotype of the standard "L. monocytogenes" prototype strain (ATCC-15313). The hemolytic activity was observed in 29 (96.7(per cent)) strains when incubated at 37ºC, but not at 4ºC. The direct colony hibridizatioon method for hemolysin gene detection showed a positive reaction with other "Listeria" spp. The PI-PLC was produced by (90(per cent)) of the strains analysed. There was no correlation between the six identified ribotypes and the virulence facors (hemolysin and PI-PLC) studied