PREVENTIVE AND THERAPEUTIC EFFECTS OF LACTOBACILLI ON URINARY-TRACT INFECTIONS IN MICE

Lactobacilli are part of the normal flora of the urogenital tract, and are used to restore the bacterial balance of the gastrointestinal, ur ogenital and respiratory tracts. We studied whether lactic acid bacter ia could be used as probiotics in the urinary tract in order to preven t colonization of uropathogens in the epithelium. The strains used wer e Lactobacillus fermentum CRL 1058 and the uropathogenic strains Esche richia coli and Klebsiella pneumoniae. Lactobacillus fermentum, attach ed to agarose beads, was inoculated intraurethrally into 2-month-old f emale BALB/c mice in different doses. These mice were then challenged by the same method with E. coli or K. pneumoniae. A reasonable double dose of lactobacilli (10(7) CFU per dose) was adequate to protect the mice since pathogens disappeared completely by the third day after cha llenge. Using a lower lactobacilli double dose (10(5) CFU per dose), t he number of E. coli recovered in the urogenital tract of challenged m ice was lower than in control animals, but did not disappear completel y. However, lactobacilli failed to exert a protective effect against K . pneumoniae colonization. No increase in the levels of either anti-la ctobacilli or anti-K. pneumoniae antibodies was observed up to the 25( th) day in mice treated with lactobacilli. A remarkable variation of t he level of lactate dehydrogenase and a slight increase of anti-E. col i antibodies were found in animals infected with E. coli, while polymo rphonuclear leucocytes were observed in the urine of animals infected with K. pneumoniae. A therapeutic assay against both pathogens could n ot be achieved; a decrease in the number of E. coli in the organs of a nimals treated with lacobacilli only was observed. Our results suggest that L. fermentum could be used as a probiotic to prevent and avoid u rinary tract infections caused by E. coli but not those caused by caps ulated pathogens such as K. pneumoniae. (C) 1996 Academic Press