Introduction: Lactic acid bacteria (LAB) and bifidobacteria are able to produce antimicrobial compounds to inhibit opportunisticwounding skin pathogen. The antimicrobial compounds produced are organic acids, putative bacteriocin, hydrogen peroxide, and diacetyl. Staphylococcus epidermidis is well-known as an opportunistic wounding skin pathogen in wound infections related to implanted medical devices.
Objective: To screen 87 strains of LAB and 3 strains of bifidobacteria for antimicrobial activity against Staphylococcus epidermidis.Additionally, this study sought to determine and quantify types of antimicrobial compounds produced by LAB.
Materials and methods: Inhibitory activity of LAB and bifidobacteria on S. epidermidis was assessed with the spectrophotometric method using a 96-well microplate reader. Characterization of cell-free supernatant (CFS) was done using analytical methods. Lactobacillus fermentum (collected by the Bioprocess Department at the Universiti Sains Malaysia [BD]) 1912d, Lactobacillus casei BD 1415b, Lactobacillus fermentum BD 8313a, Pediococcus pentosaceus BD 1913b, and Weissella cibaria (collected by the Food Technology Department at the Universiti Sains Malaysia [FTDC]) 8643 with high percentage of inhibition (P < 0.05), ranging from 73.7% to 88.2%, as compared to the control, were selected for subsequent analyses. Upon neutralization, the antimicrobial activity showed a drastic drop (P < 0.05) in the percentage of inhibition. Concentrations of the inhibitive metabolites were produced in varying amounts and were strain dependent.
Results: Results demonstrated that lactic acid in all strains was produced in a more predominant amount than acetic acid. Protein concentration production ranged from 0.081-0.215 mg/mL. L. fermentum BD 1912d yielded as much as 0.014 mg/mL hydrogen peroxide, which was significantly higher than other strains studied. Diacetyl was produced in a higher concentration by Weissella cibaria FTDC 8643 at 2.884 ng/mL; the lowest concentration of 0.465 ng/mL was produced by Ped. pentosaceus BD 1913b.
Conclusion: Antimicrobial metabolites from CFS of lactic acid bacteria were effective in repressing the growth of opportunistic wounding dermal pathogen Staphylococcus epidermidis.