Antibacterial Potentiality of Commercially Available Probiotic Lactobacilli and Curd Lactobacilli Strains, Alone and in Combination, against Human Pathogenic Bacteria

Abstract

Background and objective: Lactobacilli are excellent antibacterial agents; however, scientific study on their combined action against human pathogenic bacteria is skimpy. The current study determines the antibacterial activity of commercially available probiotic lactobacilli and the curd lactobacilli, alone and in combination, against clinical bacterial isolates. Methods and findings: Two curd lactobacilli (Lactobacillus animalis and L. gasseri) and two commercially available probiotic lactobacilli (L. acidophilus and L. rhamnosus) strains were tested for their antibacterial activity against the clinical bacterial isolates: Escherichia coli and Klebsiella pneumoniae, following agar-overlay method. The ‘R’ values (width of clear zones) due to their action against the indicator bacteria were recorded, and growth inhibitory indices (GIIs) were calculated from their combined action. The commercial lactobacilli strains, for which the ‘R’ values ranged 8-12 mm, from single action, had synergistic activity when used in combination against E. coli (GII: 0.56), while the curd lactobacilli strains having ‘R’ values 6.5-9.5 mm had synergistic activity against both E. coli and K. pneumoniae (GIIs: 0.65-0.74). The lactobacilli strains isolated were multidrug resistant. Conclusion: The current findings suggest the usefulness of natural curd lactobacilli as well as the commercially available lactobacilli strains, alone or in combination, or in combination with some conventionally used antibiotics, as therapeutics against bacterial infection to humans.