Phenotypic and genotypic characterization of listeria species isolated from poultry and milk products

Abstract

Listeria monocytogenes has become increasingly important as a food-associated pathogen. It cancause a rare but serious disease called listeriosis with high fatality rates (20–30%) compared withother foodborne microbial pathogens. To estimate the incidence and levels of Listeria spp. indifferent food sources, A total of 200 random samples which collected from different sources 65samples isolated from poultry , 45 from poultry byproducts (Frozen chicken meat balls (kofta),Frozen chicken burger and frozen chicken sausages), 20 from pasteurized milk ,30 from milkproducts (Feta cheese ,cream cheese )and 40 from poultry eggs .Only 7 of total 200 samples (14%)that collected from suspected isolates and detected on Oxford agar, PALCAM agar and ALOA agarwere suspected to be Listeria spp. In poultry, poultry byproducts, pasteurized milk, milk byproductsand poultry eggs, listeria percentage were 0/65(0%), 4/45(1.8), 0/20(0%), 0/30(0%), 3/40(1.2%)isolates, respectively. The in-vitro antimicrobial sensitivity test showed that the isolated L.monocytogenes were sensitive to Sulphamethoxazole /trimethoprim, Gentamycin, Ceftazidime andCephazoline followed by Sulphamethoxazole, ceftriaxone , weak sensitivity to Penicillin . Whilethey were resistant to Erythromycin, Clindamycin, Ampicillin. The results of virulence tests forisolated listeria strains appeared that all of L .monocytogenes were virulent strains as all of themwere positive to CAMP test; showed narrow zone of β–hemolysis on sheep blood agar .The PCRresults for Listeria isolates showed that all strains are L. monoctogenes and have Inl A and hly Agenes positive as virulence genes while negative Inl B, iap and prf A genes.