This study was conducted to learn about the potential of bacteriocins, formed by lactic acid bacteria, as inhibitory agent against Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella specie. Nine lactic acid bacteria namely Lactobacillus bulgaricus (four strains), Lactobacillus acidophilus and Lactobacillus plantarum (two strains), Lactobacillus helvaticus (two strains) and Lactobacillus acidophilus were isolated from milk and yogurt. These isolates were identified morphologically and biochemically by standard methods. Bacteriocins were separated from the bacterial cultures, by centrifugation and their antibacterial activity was tested by well diffusion method. Isolated bacteriocin indicated the inhibitory effect against S. aureus and P. aeruginosa and Salmonella specie. The strongest inhibitory activity was shown by the strain M26 against P. aeruginosa which formed an inhibition zone of 21 mm. The most sensitive pathogen to the antibacterial activity of all bacteriocin producing lactic acid bacteria was Salmonella specie. The bacteriocins extracted from these nine lactic acid bacteria retained their activity after treating with temperatures 37^oC and 45^oC but decreased at 60^oC 80^oC and 90^oC. The bacteriocins also retained their antibacterial activity after the change in pH value (4, 6, and 8). The result of this study determined that bacteriocins are quite useful against commonly known clinical pathogens and thus can be used against these pathogenic bacteria.

Key words: Lactobacillus helvaticus, antibacterial, Salmonella, Lactobacillus acidophilus, Pathogens