Inhibitory effects of Lactobacillus fermentii and Lactococcus lactis against Pseudomonas aeruginosa biofilms

Abstract

Probiotics and their derivatives are becoming increasingly popular in the fight against pathogenic biofilms. This research work explores the use of probiotic bacteria and their potential as antimicrobial agents against Pseudomonas aeruginosa biofilms and the infections they cause. P. aeruginosa strains were grown on LB (Lysogeny Broth) for 24 hours and characterized using biochemical tests. The biofilm-forming strains were quantified using polystyrene microtiter-plates in a spectrophotometric assay supplemented with M63 minimal media. LAB (Lactobacillus fermentii and Lactococcus lactis) were isolated from fermented maize paste (ogi), Cheese (Waara), Fura and fermented milk (Nunu) on Skim milk agar and were characterized based on colony morphology, cell morphology and biochemical tests. From the isolates, two strains of LAB were selected as probiotics. They were tested for their inhibitory potential against biofilm-forming P. aeruginosa using liquid co-culture assay. The Lactic acid content and Hydrogen Peroxide was estimated by titration for three days. Lactococcus lactis had more stable lactic acid production than Lactobacillus fermentii (2.70 g/L) although both peaked on Day 2 with Lactococcus lactis producing slightly more lactic acid (2.72 g/L). With liquid co-culture assay, there was a 63% decrease observed in the optical density of biofilms. Keywords: Probiotics, Lactic Acid Bacteria, Biofilm, Lactic acid, Lactobacillus fermentii, Lactococcus lactis, Pseudomonas aeruginosa