Antimicrobial Activity of Intraurethrally Administered ProbioticLactobacillus caseiin a Murine Model ofEscherichia coliUrinary Tract Infection

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Abstract
The antimicrobial activity of the intraurethrally administered probioticLactobacillus caseistrain Shirota againstEscherichia coliin a murine urinary tract infection (UTI) model was examined. UTI was induced by intraurethral administration ofEscherichia colistrain HU-1 (a clinical isolate from a UTI patient, positive for type 1 and P fimbriae), at a dose of 1 × 106to 2 × 106CFU in 20 μl of saline, into a C3H/HeN mouse bladder which had been traumatized with 0.1 N HCl followed immediately by neutralization with 0.1 N NaOH 24 h before the challenge infection. Chronic infection with the pathogen at 106CFU in the urinary tract (bladder and kidneys) was maintained for more than 3 weeks after the challenge, and the number of polymorphonuclear leukocytes and myeloperoxidase activity in the urine were markedly elevated during the infection period. A single administration ofL. caseiShirota at a dose of 108CFU 24 h before the challenge infection dramatically inhibitedE. coligrowth and inflammatory responses in the urinary tract. Multiple daily treatments withL. caseiShirota during the postinfection period also showed antimicrobial activity in this UTI model. A heat-killed preparation ofL. caseiShirota exerted significant antimicrobial effects not only with a single pretreatment (100 μg/mouse) but also with multiple daily treatments during the postinfection period. The otherLactobacillusstrains tested, i.e.,L. fermentumATCC 14931T,L. jenseniiATCC 25258T,L. plantarumATCC 14917T, andL. reuteriJCM 1112T, had no significant antimicrobial activity. Taken together, these results suggest that the probioticL. caseistrain Shirota is a potent therapeutic agent for UTI.