Characteristic of Antimicrobial Activity of Lactobacillus Species Isolated From Yoghurt in Khartoum State

Abstract

This research was conducted to determine the antibacterial effects among the "probiotics isolated from yoghurts against some common bacterial pathogens, After collection, samples were serially diluted in sterile distilled water then 0.2 ml of 10-5-10-7 dilutions from each sample was transferred to sterile plates of De-Mann, Rogosa and Sharpe agar (MRS) medium. All distinct and well isolated colonies were sub-cultured to get pure colonies and examined for various morphological characteristics. Biochemical tests was done to isolates by inoculation in the Bromothymol blue base medium containing different sugar substrate. Characterization of probiotic properties was done by inoculating the isolates in MRS medium containing different concentration of NaCl ,bile salt and PH values after incubation period colonies counted using colony conunter. Antimicrobial sensitivity was done by well diffusion method.. The antimicrobial assay was performed on six types of pathogenic bacteria (Bacillus spp, Shigella, Protus, Escherichia coli, Klebsiella spp, Pseudomonas aeruginosa and salmonella typhi ). After incubation, the plates were examined for zones of inhibition. Results showed the presence of antibacterial effects among the probiotics that were isolated from yoghurts. The spectrum of their antibacterial effects varied against the selected pathogenic bacteria. Antibacterial effects are one of the most important selection criteria for probiotics, and the verified antibacterial activity of the probiotics supports the development of these functional foods as a key to the improvement of health in the consumers .