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

Document Type : Original Article


1 Department of Bacteriology, Immunology and Mycology, Faculty of Veterinary Medicine, Benha University

2 Animal Health Research


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.