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

Ashraf A. Abd El-Tawab1 , Wafaa, M.M Hassan 2 , Fatma I El-Hofy1 and Haidy,T.Zaki 2


Listeria monocytogenes has become increasingly important as a food-associated pathogen. It can cause a rare but serious disease called listeriosis with high fatality rates (20–30%) compared with other foodborne microbial pathogens. To estimate the incidence and levels of Listeria spp. in different food sources, A total of 200 random samples which collected from different sources 65 samples 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 milk products (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 agar were suspected to be Listeria spp. In poultry, poultry byproducts, pasteurized milk, milk byproducts and 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 and Cephazoline followed by Sulphamethoxazole, ceftriaxone , weak sensitivity to Penicillin . While they were resistant to Erythromycin, Clindamycin, Ampicillin. The results of virulence tests for isolated listeria strains appeared that all of L .monocytogenes were virulent strains as all of them were positive to CAMP test; showed narrow zone of β–hemolysis on sheep blood agar .The PCR results for Listeria isolates showed that all strains are L. monoctogenes and have Inl A and hly A genes positive as virulence genes while negative Inl B, iap and prf A genes.

Key words

L. monocytogenes, poultry, milk.

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