Traditional fermented beverages that contain lactic acid bacteria have antimicrobial activity for various human pathogens and used for preservation of beverages for a long time. However, there is no scientific report on the antimicrobial activity of lactic acid bacteria isolated from different beverages in Gondar town. The objective of the study was to isolate and screen lactic acid bacteria that show antibacterial activity against clinical and standard human pathogens. Samples of “Ergo” and “Tej” were collected from Arada, Azezo and Kebele 18. A volume of 0.1ml suspension from 10-6 dilution of each sample was spread on MRS agar plates and incubated both in aerobic and anaerobic conditions. Morphologically distinct colonies were subcultured to MRS broth and incubated at 37 0C for 72 hrs in thermostat water bath. The broth culture was centrifuged and the supernatant was used to check the antimicrobial activity against clinical and standard pathogens using agar well diffusion assay. The amount of lactic acid and H2O2 produced by the isolates during fermentation was determined using color change after titration. From a total of 18 selected isolates, the cell free supernatant of I2 and I3 were able to inhibit the growth of all clinical and standard human pathogens used in this study. The antibacterial activity of the supernatant from I2 (12.3+1.6 mm to 16+1.7 mm) and I3 (10+1 mm to 15.7+1.2 mm) were effective compared to Ampicillin (0 to 11+1mm). The maximum amount of lactic acid was recorded at 72 hrs incubation time by both I2 (1396.24 mg) and I3 (810.72 mg). Moreover, much amount of H2O2 was produced at 72 hrs incubation time by I2 (3.7 mg) and I3 (5.35 mg). Thus, isolation and screening of lactic acid bacteria from potential fermented drinks are the sources of antibacterial agents for the treatment of human pathogens. This can give direction for finding antibacterial agent producing microorganisms from fermented drinks use for preservation of foods as well as prevention of health risk problems associated with food borne diseases.
Keywords: Antimicrobial activity, “Ergo”, Gondar town, Lactic acid bacteria, “Tej”