Incidence of Listeria species from food products.

Abstract

By its implication in the public health, the food contamination with L. monocytogenes raises an important economic problem concerning the food industry. The presence of Listeria spp. proved to be a useful indicator during all the stages of the food processing chain. A total number of 30 strains of Listeria spp. were investigated for identification/ confirmation. These strains were isolated from animal meat (raw minced meat, muscular tissues, sausages and other pork and beef preparations), poultry and diary products. The bacterial identification included morphological (Gram staining, microscopic examination, motility, oblique illumination of colonies on blood-free agar) and biochemical (catalase, beta-hemolysis on 5% sheep blood agar, CAMP test, trehalose, mannitol, manose, rhamnose, xilose reactions) methods. L. monocytogenes strains were serotyped for serovar identification. The investigations finally revealed: 8 strains (26.66%) L. monocytogenes (out of which 7 strains L. monocytogenes serotype 1a, and 1 strain L. monocytogenes serotype 4b), 19 strains (63.33%) L. innocua, 1 strain (3.33%) L. grayi, and 2 strains (6.66%) L. welshimeri.