Probiotics are cultures of viable microorganisms, which show a positive effect on the general condition of the host when administered. Among the lactic acid bacteria (LAB), lactobacilli are the most commonly used for probiotics, and they have an excellent safety record. In terms of UTI, weekly or twice weekly intravaginal instillation of Lactobacillus strains GR-1 and B-54 have led to reduced recurrences. This concept has been supported by a 2006 pilot study showing that intravaginal administration of Lactobacillus crispatus GAI 98322 every two days for one year, had the potential to reduce the UTI recurrences. Another approach has been taken whereby lactobacilli are administered orally with a view of simulating how the pathogens reach the vagina. The studies have shown that L. rhamnosus GR-1 and L. reuteri (formerly fermentum) RC-14 can reach the vagina after daily oral ingestion, and they can lower the bacterial and yeast pathogen numbers.