Competitive exclusion of uropathogens from human uroepithelial cells by Lactobacillus whole cells and cell wall fragments.

Previous studies have shown that indigenous bacteria isolated from cervical, vaginal, and urethral surfaces of healthy women are able to adhere to human uroepithelial cells in vitro. Furthermore, these organisms were found to block the adherence of uropathogenic bacteria to uroepithelial cells from women with and without a history of urinary tract infections. In the present study, complete or partial inhibition of the adherence of gram-negative uropathogens was achieved by preincubating the uroepithelial cells with bacterial cell wall fragments isolated from a Lactobacillus strain. Competitive exclusion was most effective with whole viable cells and less effective with cell wall fragments obtained by sonication, extraction with sodium dodecyl sulfate, and treatment with sodium dodecyl sulfate and acid. Analysis of the Lactobacillus cell wall preparations suggested that lipoteichoic acid was responsible for the adherence of the Lactobacillus cells to uroepithelial cells but that steric hindrance was the major factor in preventing the adherence of uropathogens. This conclusion was also supported by blockage studies with reconstituted lipoteichoic acid-peptidoglycan, which was more effective at blocking adherence than lipoteichoic acid or peptidoglycan alone. The results suggest that the normal flora of the urinary tract may be used to protect against the attachment of uropathogens to the surfaces of uroepithelial cells. The long-term implications of these findings may lead to alternative methods for the management and prevention of recurrent urinary tract infections in females.