Vaginal Lactobaccilus Isolates Show Probiotic Potential

By Anne Harding

June 11, 2020

NEW YORK (Reuters Health) - Several vaginal Lactobacillus strains isolated from South African women show strong in vitro probiotic effects, outperforming commercially available probiotics, new findings show.

Researchers are hopeful the best-performing strains could be used to treat bacterial vaginosis (BV), which occurs when Lactobacillus strains are depleted and populations of anaerobic bacteria increase, altering vaginal pH and increasing the risk of sexually transmitted infections and adverse pregnancy outcomes if left untreated.

"Bacterial vaginosis is the most common inflammation-causing condition in women, and the current standard of care internationally is antibiotics, which don't work in the majority of women," Dr. Jo-Ann Passmore of the University of Cape Town, in South Africa, told Reuters Health in a video call. Within six months, she noted, most women will have recurrent infections.

Dr. Passmore and her colleagues isolated 57 Lactobacillus strains from 26 young women, including 10 L. crispatus strains, nine L. gasseri strains, 18 L. jensenii strains, eight L. vaginalis strains and 12 L. mucosae strains. They compared them to four Lactobacillus ATCC reference strains and 10 Lactobacillus strains from commercial probiotics.

The researchers also included isolates from women with BV (n=10) and/or sexually transmitted infection (STI, n=6) in the analysis.

The vaginal strains were able to grow at pH 6.0, and all lowered culture pH, the team reports in PLoS Pathogens. L crispatus strains had the strongest effect, lowering in vitro pH to 3.7.

Most of the vaginal strains produced more L- and/or D-lactate than the reference strains. Most vaginal strains inhibited the growth of Prevotella bivia, although the effect was lower and more variable for inhibition of Gardnerella vaginalis.

All of the vaginal L. crispatus isolates and most of the vaginal isolates from other strains were strongly adherent to ectocervical cells in vitro and without damaging the cells or promoting inflammation.

The vaginal strains were also resistant to metronidazole, meaning they could be administered along with the drug, while most were not resistant to clindamycin. Whole genome sequencing of five of the best-performing strains did not identify major antimicrobial resistance elements.

The department of chemical engineering at the University of Cape Town is now working with the best-performing strains to determine the best way to formulate them for use as probiotics, Dr. Anna-Ursula Happel of the University of Cape Town, the study's first author, told Reuters Health in a video call.

"The idea is basically to have a pilot product that then would be tested in a small clinical study first to make sure it's really safe," Dr. Happel added.

"In South Africa women's access to health care in general is very limited. The majority of these cases go undiagnosed and treated," Dr. Passmore said. The goal, she added, is to develop an affordable product that women could use on their own to prevent BV.

SOURCE: PLoS Pathogens, online June 4, 2020.