الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
A total of 430 Enterococcus spp. isolates and 200 Escherichia coli isolates were recovered from different dairy products, the stool of apparently healthy human volunteers and various clinical specimens. The recovered isolates were screened for bacteriocin-production using the agar well diffusion method. Bacteriocin-like inhibition was detected in 71.1% of the tested Enterococcus spp. isolates against reference Staphylococcus aureus (ATCC 25923) whereas only 26.5 % Enterococcus spp. isolates showed inhibition against reference Escherichia coli (ATCC 25922). On the other hand, 20% and only 5% of the tested Escherichia coli isolates showed bacteriocin-like inhibition against the reference S. aureus strain and reference E. coli strain, respectively. Bacteriocin production was confirmed by excluding the possible interfering effects of organic acids and hydrogen peroxide prior to antimicrobial activity testing. Besides, protease susceptibility testing was performed in order to determine the nature of the tested CFSs. The activity of the neutralized CFSs was tested by agar well diffusion assay before and after treatment with the proteolytic enzyme; proteinase K. Loss of activity after treatment suggested that the inhibitory substances responsible for antimicrobial activity of the tested CFSs were protein in nature. Therefore, they were considered bacteriocins. The overall detection rate of bacteriocin production in our study was 6.9% in case of Enterococcus spp. isolates and was experimentally non-detectable in case of the tested Escherichia coli isolates. The highest proportion of bacteriocin–producing Enterococci was detected among clinical isolates 46.7%, followed by dairy products 33.3% and fecal isolates 20%.