Lactobacillus species in the lower reproductive tract of healthy women lower vaginal pH and protect against sexually transmitted infections. But women commonly suffer from bacterial vaginosis - a disruption in the optimal Lactobacillus-dominated genital microbiota - resulting in higher vaginal pH as well as vaginal discharge and inflammation.
Bacterial vaginosis is associated with adverse pregnancy outcomes and a higher risk of sexually transmitted infections, including HIV. Although antibiotics are the standard of care for bacterial vaginosis, most cases recur within six months. Probiotics that include Lactobacilli have been explored to improve the durability of treatment, but the majority of products do not contain species commonly found in the female genital tract (FGT).
Lead author Jo-Ann Passmore, of the University of Cape Town, says there's a limited variety of probiotics for vaginal health are currently available internationally and in South Africa and very few of these contain strains found in the FGT.
The new study, published in PLOS Pathogens, aimed to isolate and evaluate key characteristics of vaginal Lactobacillus strains from South African women to select the 'top performing' strains for the development of a probiotic for vaginal health.
Using a sample of 26 young (median age 18 years; IQR 17–19 years) South African women, Passmore and colleagues compared the characteristics of five different Lactobacillus strains in the women - L. crispatus, L. gasseri, L. jensenii, L. vaginalis, and L. mucosae - to four ATCC (American Type Culture Collection) reference strains - L. crispatus, L. gasseri, L. jensenii, and L. vaginalis - and three strains from commercially available probiotics - L. reuteri, L. rhamnosus and L. acidophilus.
They analysed their growth at varying pH values, ability to lower pH and produce antimicrobial products, pathogen inhibition, and susceptibility to antibiotics.
They found that several vaginal strains exhibited 'better probiotic profiles than commercial strains'. The authors say this suggests the vaginal strains would be beneficial in the development of probiotic treatments for bacterial vaginosis.
Moreover, the researchers say that whole-genome sequencing of the five best-performing vaginal strains revealed that they would likely be safe and not pose a risk of antimicrobial resistance.
"Few probiotics aimed at promoting vaginal health contain Lactobacillus spp. that commonly colonise the lower genital tracts of African women," the authors add. "The discovery and use of novel vaginal probiotic strains in such women may improve the durability of bacterial vaginosis treatments and towards this end Happel et al. (2020) evaluated a multitude of vaginal Lactobacillus strains and identified some that should be tested as vaginal probiotics in clinical trials in Africa."
Source: PLoS Pathogens
Happel A-U, Kullin B, Gamieldien H, Wentzel N, Zauchenberger CZ, Jaspan HB, et al. (2020)
"Exploring potential of vaginal Lactobacillus isolates from South African women for enhancing treatment for bacterial vaginosis."