Antibacterial effect of on and isolated from raw milk and some dairy products with special reference to biofilm gene expression.

Background: ( ) and () are well defined as food poisoning pathogens that are highly resistant and need continuous studies.

Aim: The purpose of the work was to examine phenotypic and genotypic characteristics of both and , and treatment trials with medicinal plants.

Methods: Samples were examined for isolation of and on selective media followed by biochemical confirmation, biofilm formation, genes detection and expression of biofilm gene was performed by quantitative real-time polymerase chain reaction after treatment with 0.312 mg/ml aqueous extract as a minimum inhibitory concentration.

Results: The highest isolation rate of was 20% from both raw milk and Kariesh cheese, followed by 16% and 12% from ice cream and processed cheese, respectively, while the highest isolation rate of was 36% from raw milk followed by 28% in ice cream and 16% in both Kariesh cheese and processed cheese. 30% of isolates were biofilm producers, while only 21% of isolates were able to produce biofilm. The isolates harbor virulence-associated genes , , , and at 100%, 80%, 40%, and 40%, respectively. genes were examined in strains, where and genes were detected with 60%, but no isolate harbored , , or . The significant fold change of expression was 0.40332 after treatment with aqueous extract.

Conclusion: and harbor dangerous virulence genes that cause food poisoning, but extract could minimize their action.