Antibacterial activity of lactic acid bacteria isolated from traditionally fermented food against food pathogen

Aim: To evaluate the antibacterial activity of lactic acid bacteria against selected food pathogens (Escherichia coli and Staphylococcus aureus).

Method: A total of twenty (20) traditionally fermented food samples were purchased from a market in Umuahia metropolis. Isolation and identification of lactic acid bacteria (LAB) were conducted using standard microbiological techniques. LAB were identified using standard morphological and biochemical tests. They were tested against food pathogens using the Agar well diffusion method.

Results: The isolated lactic acid bacteria include Lactobacillus fermentum, Lactobacillus acidiophilus, Lactobacillus casei and Lactobacillus plantarum and were label as SP1, SP2, SP3, and SP4 respectively. The isolated LAB species had a considerable inhibitory effect on food borne pathogens. Cell free supernatant of four species were tested for antagonistic activity at 24hrs and 48hrs incubation time. Cell free supernatant from 48hrs broth of SP1 showed the highest zone of inhibition on Escherichia coli (28mm) while the cell free supernatant from 24hrs broth of SP4 showed the lowest zone of inhibition on Staphylococcus aureus (13 mm).

Conclusion: The antimicrobial activity increases with time. LAB demonstrated high antimicrobial properties against food borne pathogens. This potential can be employed as starters in food industry to inhibit food spoilage microbes and contaminants.