Effect of lactobacilli and antibiotics on E. coli urinary infections in mice.

Urinary antibiotic treatments usually affect the normal urethral flora. This work was developed in order to evaluate whether Lactobacillus fermentum CRL 1058 could reduce urinary tract infections (UTI) produced by uropathogenic Escherichia coli in mice treated with antimicrobial agents. Animals were inoculated intra-urethrically with agarose beads containing lactobacilli, and were challenged with E. coli. Ampicillin (13 mg/kg/dose) was administered orally. The number of microorganisms present at different days was evaluated in the urogenital tract. Serum inflammatory and systemic immune response were also registered. The use of 5 doses of ampicillin after 3 doses of lactobacilli in agarose beads significantly affected the viability of lactic acid bacteria, while the amount of E. coli was not altered. Lactate dehidrogenase (LDH) activity and anti-E. coli antibody levels showed no statistically significant difference between the challenged and non-challenged mice. Lactobacilli reinoculation and 3 doses of ampicillin proved to be a moderately effective treatment since a smaller amount of E. coli was recovered from the organs of treated mice than from the controls. The reinforcement of lactobacilli, administered on the 9th day, produced a faster elimination of the pathogen. The ampicillin dose used allowed lactobacilli permanence in the urinary tract, and caused the elimination of the pathogen. Serum LDH values seemed to show an inflammatory immune response. No successful preventive results could be achieved. We can conclude that lactobacilli and adequately low doses of ampicillin have a positive effect on the treatment of E. coli in this UTI model.