A.M. El-Kholy¹, S.H. El-Shinawy^1,, A.M.S. Meshref¹, A.M. Korny¹

The objectives of this study were to assess the microbiological quality of Egyptian yoghurt and to investigate the antagonistic activity of some probiotic bacteria against some food borne pathogens in vitro and in yoghurt. The results indicated a poor microbiological quality of yoghurt, the microbiological parameters recorded higher values than admissible levels. Results from the agar spot test and well diffusion assay showed the capability of probiotic bacteria to inhibit the growth of S. aureus, E. coli O157:H7 and L. monocytogenes in vitro. Yoghurt produced from milk artificially contaminated with S. aureus and E. coli O157:H7 was used for studying the ability of L. acidophilus La-5 and B. longum ATCC15707 to inhibit the growth of such pathogens. During the refrigerated storage the counts of both pathogens decreased significantly in the probiotic yoghurt than control one. Survival of both L. acidophilus La-5 and B. longum ATCC15707 in yoghurt was satisfactory. Practical applications: The microbial contamination of yoghurt represents not only spoilage of the product but also constitutes a high risk to human health. Survival of probiotic bacteria in yoghurt was satisfactory, which indicate the suitability of yoghurt as a vehicle for probiotic bacteria. The probiotic bacteria have the ability to prevent the growth of E. coli O157:H7, S. aureus and L.monocytogenes in vitro and in yoghurt.

probiotics, S. aureus, E. coli O157:H7, yoghurt, quality