Impact of Probiotic Strains on Growth of Some Food Poisoning Bacteria from Milk and Soft Cheese

Abstract

One hundred and twenty samples, 40 each of raw milk, Kareish cheese (raw skim milk soft cheese) and Damietta cheese (white raw milk soft cheese) were collected from supermarkets, dairy shops and street vendors in El- Gharbia governorate, Egypt for microbiological investigation. The obtained results revealed that S. aureus, E. coli and B. cereus could be detected in 60, 52.5 & 20%; 25, 37.5 & 15% and 12.5, 15 & 7.5% of examined samples, respectively. Serological typing of fourteen strains of isolated E. coli proved to belong to ten serotypes; O159, O142, O18, O15, O125, O111, O55, O119, O26 and O128. Salmonella typhimurium could be isolated from one Kareish cheese sample (2.5%) with serological typing proved that the strain has antigenic structure of O: 1, 4, 5, 12, H: i: 1, 2. Concerning the antimicrobial activities of some probiotic bacteria; Lactobacillus planterum (p 1 ), Lactobacillus acidophilus (p 7 ), Lactobacillus brevii (p 102 ) and Lactobacillus casii (l.c) using an agar well diffusion assay against selected isolates of E. coli, B. cereus, S. aureus and Salmonella typhimurium indicated that the used probiotic bacteria appeared to have antimicrobial effect against E. coli and B. cereus, while induce no antimicrobial effect against S. aureus and Salmonella typhimurium. The same probiotic strains were injected with E.coli in sterilized skim milk as in vitro experiment and the results showed a significant reduction in the count of E. coli during the periods of incubation.