Microbiology Research Journal International

Lactic acid bacteria (LAB) are known to be sources of various antimicrobial metabolites that are harmless to humans. This study aimed to evaluate the antimicrobial activity of LAB isolated from curdled milk in Burkina Faso against bacterial pathogens and toxigenic fungi and to investigate the role of LAB in bacteriocin synthesis. A total of 12 LABs were used in the study. Antibacterial activity was assessed by agar diffusion against seven pathogenic strains, including three clinical strains (Staphylococcus aureus 781, Klebsiella pneumoniae 787, Acinetobacter baumannii 844) and four reference strains (Escherichia coli ATCC25922, Staphylococcus aureus ATCC29213, Pseudomonas aeruginosa ATCC27853, Streptococcus oralis NCTC8029). Minimum inhibitory concentrations (MICs) were determined at 20 mg/mL for all the strains tested. All the strains tested showed inhibition against Staphylococcus aureus, with diameters ranging from 13 mm (V1, V24) to 31 mm (Vr5).  Finally, the strongest inhibitory activity was observed against Klebsiella pneumoniae with strain Vr1, which produced a 35 mm zone of inhibition. However, no minimum bactericidal concentration (MBC) was observed at the maximum concentration tested. Antibacterial activity was found to be predominantly bacteriostatic. In terms of antifungal activity, comparison tests revealed a wide range of fungal inhibition percentages, from 0% to 100%. From 12 LAB isolates screened, five strains were selected for their strong antifungal activity, corresponding to two Enterococcus sp., two Lactococcus sp., and one Pediococcus sp. PCR identified two types of bacteriocin synthesis genes in 6 out of 12 LAB strains, indicating their potential for bacteriocin production.