Abstract
Urinary tract infections are the most common infectious diseases in babies and the elderly and are often acquired as nosocomial infections. The purpose of the present study was to identify strains of lactic acid bacteria (LAB) which could be used as alternatives to antibiotics for the treatment of urinary tract infections because of their ability to inhibit urinary tract pathogens (Klebsiella pneumoniae BCRC 10694 and Gardnerella vaginalis BCRC 17040). We screened 370 LAB strains using spent culture supernatants by inhibition zone assay to assess their antimicrobial effects. We studied the effect of heat, pH and enzyme treatment on the inhibitory activity of LAB strain supernatants. Anti-growth activity against urinary tract pathogens was evaluated by co-culture inhibition assay using seven LAB strains. Anti-adhesion and anti-invasion activities against urinary tract pathogens were evaluated by SV-HUC-1 uroepithelium cell culture. The results showed that the supernatants had good heat stability. However, antibacterial activity disappeared entirely at pH 7.0. After enzyme treatments, the supernatants showed first- or second-order inhibitory effects on K. pneumonia BCRC 10694. The survival rate of urinary tract pathogens was 0-10.65% and pH of the culture medium decreased after co-culture with LAB strains for 4 h. In a competition assay, PM2 and RY2 inhibited urinary tract pathogens. PM68, PM78, PM201, PM206 and PM229 inhibited the invasion of SV-HUC-1 cells by G. vaginalis BCRC17040. In conclusion, PM78, PM229 and RY2 showed the strongest inhibitory activity against urinary tract pathogens and could be suitable for use in the treatment of urinary tract infections.