Vaginal microbiota and urinary tract infections in women: the protective role of vaginal lactobacilli in counteracting urinary tract infections occurrence and recurrence

Urinary Tract Infections (UTIs) are common clinical conditions. Women are affected by UTIs more than men and their probability of experiencing such conditions is high (60%). The vagina and its defensive system play a key role in the pathogenesis of UTIs, making the vaginal microbiota (VMB) a target for controlling UTIs and their recurrence (rUTIs). Current therapy consists of low-dose antibiotics for rUTIs prevention. The increasing incidence of antimicrobial resistance documented to date has rendered this strategy less attractive. The initial step of UTIs pathogenesis involves colonization of the vaginal introitus and periurethra by uropathogens. The following steps may include the ascension of uropathogens via the urethra to the bladder and kidneys. Vaginal infections may be caused by uropathogens from the intestinal microbiota, taking advantage of the proximity between the anus and the vagina. Nevertheless, uropathogens may arise from the vagina itself because of alterations in VMB. Changes in VMB lead to Bacterial Vaginosis (BV), which consists of the replacement of healthy lactobacilli with unhealthy Gram-negative bacteria, such as <i>Escherichia coli</i>. The documented relationship between BV and UTIs supports the intriguing hypothesis that restoring VMB may represent a new option to control UTIs and rUTIs after short-term antibiotic treatment in a safe and cost-effective manner.