Urogenital probiotics : potential role of Lactobacillus in the prevention of urogenital infections in women

Abstract: The human vaginal ecosystem is dominated by Lactobacillus species. An altered vaginal flora can result in symptomatic conditions such as bacterial vaginosis and vulvo-vaginal candidiasis, and urogenital colonisation by uropathogenic bacteria can cause urinary tract infection. The protective role of lactobacilli is gradually being accepted and clinical studies have been carried out in order to evaluate the use of promising probiotic bacteria, which are defined as “live microorganisms which when administered in adequate amounts confer a health benefit on the host”. This thesis includes an investigation into the ecological role of lactobacilli in the genital tract in healthy women, with respect to the relationship to other species and vaginal pH. Furthermore, in order to find different probiotic strains with promising probiotic qualities, Lactobacillus strains were screened in two diverse screening processes. The selected strains were further evaluated in clinical trials. The prevalence of group B streptococci (GBS) and yeast was significantly dependent on the number of vaginal lactobacilli among healthy women. GBS were less frequently found in women with high numbers of vaginal lactobacilli than in women with low numbers and the prevalence of yeast was significantly higher in women with 3-6.99 log10 lactobacilli sample-1 than in women with less than 3 or ≥7 log10 lactobacilli sample-1. Furthermore, the first screening made on 511 strains isolated from the female genital tract resulted in the final selection of a Lactobacillus plantarum, designated LB931. The screening showed that LB931 had a strong technical growth, survived through freeze-thawing, produced substances bactericidal to uropathogenic bacteria and was a rapid and strong producer of hydrogen peroxide. Further characterisation showed that LB931 possessed the properties required for probiotics with the capability to prevent urogenital infections. LB931 could be supplied to the genital tract through the usage of panty liners impregnated with the strain. In the second screening, Lactobacillus fermentum, designated Ess-1, was the only one out of 126 Lactobacillus strains with strong capacity to inhibit Candida albicans and Candida glabrata. Additional characterisation showed that L. fermentum Ess-1 had the properties that are needed to prevent over-growth of Candida in the vulvo-vaginal tract. The result of the case study showed that a high and frequent dosage of Ess-1 is needed and that improved vulvo-vaginal candidiasis specific diagnostic criteria are required. In conclusion, L. plantarum LB931 and L. fermentum Ess-1 are promising probiotic strains to be used in the prevention of recurrent urogenital infections in women and to enhance the normal flora in healthy women.