Anti-Bacterial Activity of Substances Produced from Lactic Acid Bacteria in Metata Ayib (Traditional Ethiopian Spiced Fermented Cottage)

Abstract

There have been incerases in antibiotic resistant strains of human pathogens and causing treatment of microbial infections difficult. These days more attention is given to seraching new antimicrobial drugs to combat pathogenic microbes. Traditional fermented cottage of Metata Ayib which is naturally enriched with lactic acid bacteria (LAB) and used to preserve cheese for long time in Northern Ethiopia, may have antimicrobial activity against various human pathogens. However, there was no scientific report on the antimicrobial activity of lactic acid bacteria isolated from Metata Ayib. The objective of this study is to evaluate antibacterial activity of lactic acid bacteria from Metata Ayib against clinical and standard human pathogens. The study was laboratory based experiment. Antibiotic production by the LAB was performed by inoculating the LAB isolates into 6.0 ml MRS medium and incubating at 30 {degrees}C. Cell free supernatants (CFS) were collected by centrifugation (10,000 rpm for 15 min at 4 {degrees}C) of the six day fermented broth cultures. The pH of the CFS was adjusted to 6.5 with 4 N NaOH to eliminate the effect of organic acids.The susceptibility of produced antibiotic against test organisms was done by growing on Muller Hinton agar in triplicate using well diffusion method and the inhibition zone was recorded. Preceddingly, MIC and MBC was determined using standard methods. The antibiotic substance exhibited antimicrobial activity towards standard and drug resistant bacteral strains with the inhibition zone ranges upto 25.33{+/-}3.21 mm. The result of MIC against tested ornaisnms showed a considerable antimicrobial activity of the antibiotic substance withn the range values 6.25% to12.5%. In addition, the result of this study showed that LAB obtained from Metata Ayib exhibits antimicrobial activity against standard and pathogenic pathogenic test bacterial species ranged from 12.5-25% of MBC value. This might be due to the production of organic acids, but also other compounds, such as ethanol, hydrogen peroxide, diacetyl, reuterin and bacteriocins. The results of this investigation can also provide baseline for information for future studies about the application of antibacterial substances produced by LAB from fermented Metata ayib.