The present invention discloses novel isolated strains of lactic acid producing bacteria of the genera Lactobacillus and Pediococcus, and a method for isolation of such bacterial strains, having the ability to colonise and become established in a human vagina, even during menstrual discharge. Furthermore, a composition comprising the bacterial strains and a sanitary article comprising the bacterial strains, such as a tampon, for prophylaxis and/or treatment of infections of the urogenital tract, are described. The present invention also describes a method for prophylaxis and/or treatment of infections of the urogenital tract, wherein at least one of the bacterial strains is administered vaginally.