Lactobacillus probiotics improve vaginal health in asymptomatic women

In a recent study published in the journal Nutrients, researchers in the Republic of Korea reported that oral administration of Lactobacillus probiotics could facilitate the growth of Lactobacillus species and decrease vaginal dysbiosis in asymptomatic women.

Study: Lactobacillus Probiotics Improve Vaginal Dysbiosis in Asymptomatic Women. Image Credit: Kateryna Kon / Shutterstock

Background

Vaginal health is linked to the bacteria that comprise the vaginal microbiome, and the relative abundance of Lactobacillus species is important in arresting pathogenic microbes from invading the vagina. Lactobacillus species also play a substantial role in lowering the susceptibility to sexually transmitted infections and other gynecological infections such as bacterial vaginosis. The lactic acid produced by Lactobacillus species reduces the pH of the vaginal environment and exhibits immunomodulatory, antiviral, and antimicrobial properties.

The most commonly found Lactobacillus species in the vagina are L. crispatus, L. gasseri, L. iners, and L. jensenii. An abundance of these species indicates a healthy vaginal environment, while dysbiosis involves a decrease in the abundance of Lactobacillus species and an increase in the abundance of anaerobic bacteria such as those belonging to the genera Gardnerella, Prevotella, Megasphaera, Aerococcus, Papillibacter, Eggerthella, Leptotrichia/Sneathia, and Atopodium, which can lead to bacterial vaginosis and urinary tract infections. Therefore, oral administration of probiotics containing Lactobacillus species could decrease dysbiosis in the vaginal environment.

About the study

In the present study, the researchers used the Nugent score to screen the participants for asymptomatic bacterial vaginosis. The usual symptoms of bacterial vaginosis are irritation, itching, rashes, burning, bad odor, pain, unusual discharge, and pain in the vulvovaginal region and vagina. However, close to half the women who have bacterial vaginosis are asymptomatic.

The Nugent score, which is based on the presence of large Gram-positive rod-shaped bacteria such as Lactobacillus species and small or curved Gram-variable rod-shaped bacteria such as Gardnerella species, is used to diagnose bacterial vaginosis in asymptomatic cases. Additionally, molecular methods of diagnosis such as polymerase chain reaction (PCR) and sequencing the 16S ribosomal ribonucleic acid (rRNA) amplicon can help confirm the diagnosis and decide treatment options for bacterial vaginosis.

Therefore, the researchers used Nugent scores to initially categorize the study participants and then conducted quantitative reverse transcription polymerase chain reaction (qRT-PCR) and next-generation sequencing (NGS) of the 16S rRNA gene using cervicovaginal fluid samples to validate the microbiota found in the vaginal environment of women who had vaginal dysbiosis but were asymptomatic. Individuals were excluded if they were taking antibiotics or probiotics, were pregnant, had a history of drug or alcohol addiction, or were undergoing hormone or immune therapy.

The Lactobacillus probiotic treatment comprised a combination of strains from three species — Lactobacillus acidophilus, Lactobacillus reuteri, and Lactobacillus rhamnosus. Cervicovaginal fluid samples were collected before the treatment with Lactobacillus probiotics commenced and then twice at three-week intervals. Lactobacillus probiotics were administered for two courses of three weeks each, and cervicovaginal fluid samples were collected for NGS, Gram staining, and qRT-PCR at the end of each three-week course. An additional sexually transmitted infection-PCR was conducted for the samples obtained on the last visit.

Results

The results reported that 60% of the women with a high Nugent score experienced improvements in vaginal dysbiosis and showed lower Nugent scores after the administration of two three-week-long courses of Lactobacillus probiotics. Furthermore, the qRT-PCR results indicated colonization of the vaginal environment with Lactobacillus species.

The alpha diversity and Nugent score were positively correlated with vaginal dysbiosis, while the colonization of the vagina with Lactobacillus species was negatively correlated with the Nugent score and alpha diversity as the relative abundance of Lactobacillus species in the vaginal microbiome increased.

The shift from high to low Nugent scores indicated a change from vaginal dysbiosis towards eubiosis, which was evidenced by the high relative abundance of Lactobacillus species in the participants with low Nugent scores and the high relative abundance of Gardnerella species in the participants with high Nugent scores.

Conclusions

Overall, the results suggested that consumption of Lactobacillus probiotics can increase the colonization of the vaginal environment with Lactobacillus species and improve conditions of vaginal dysbiosis in asymptomatic women. Furthermore, the findings indicated that even in cases of no vaginal dysbiosis, Lactobacillus probiotics could help increase or maintain the abundance of Lactobacillus species in the vaginal environment.