The human vagina is home to different kinds of 'good' microorganisms, primarily bacteria, which form the vaginal microbiome. They maintain the right balance of pH, keep the vagina stable, and ward off 'bad' microorganisms that may cause an infection. Bacterial vaginosis is a condition resulting from the disturbance of this harmony in the vagina. The composition of these microbes depends on the genetics, hygiene status, and sexual behaviour of individuals. It also varies across geographical locations. Many studies have explored the differences in this composition among women belonging to different races and ethnicities. However, only a handful of them have analysed the vaginal microbiome of Indian women.
Now, a new study from researchers at the Translational Health Science and Technology Institute (THSTI), Faridabad, has decoded the bacterial species found in the vagina of pregnant Indian women by using advanced gene sequencing technology called Shotgun sequencing. The study, published in the journal Microbial Ecology, also provides genomic insights into these bacterial species found in the genital tract. The study was funded by the Department of Biotechnology (DBT) and the Grand Challenges India–All Children Thriving Program of the Biotechnology Industry Research Assistance Council (BIRAC).
"Lactobacillus is the primary bacterial genus found in the vagina of women in reproductive age. It prevents the growth of harmful bacteria and reduces the risk of urogenital diseases," says Dr Bhabatosh Das from THSTI and the corresponding author of the study.
These bacteria maintain a healthy vaginal pH by producing lactic acid and by secreting bacteriocin—proteins produced by bacteria to inhibit the growth of other species.
A timely prediction and prevention of bacterial vaginosis is a challenge because of the diversity of microbes. Treating this condition is also tricky as tests may give conflicting results, and some bacteria may develop resistance to commonly used antibiotics. In pregnant women, along with hormonal changes, vaginal microbiome composition and diversity also change which may lead to bacterial vaginosis, a potential risk factor associated with preterm delivery, miscarriage, and low birth weight of the baby. The current study focused particularly at understanding the bacterial species in the vaginal microbiome of Indian women who delivered full-term and preterm babies to aid diagnosis and treatment.
So far, the collective genomic information of vaginal microbiome and complete genome sequences of Lactobacillus species from the vaginal microbiome of Indian women do not exist.
"VIRGO, which is a huge vaginal gene catalogue, includes genomes from North American, African, and Chinese women, but there is no mention of Indian women. So, this is a definite knowledge gap and needed to be dealt with," shares Dr Das on the motivation of the study.
The researchers collected vaginal swabs from 40 pregnant Indian women across the country who were in their early stages of pregnancy. These swabs were used for metagenomic DNA extraction—a process of obtaining a mix of genomic material out of a complex bunch of multiple types of microorganisms present in their natural abode, unlike genomic DNA extraction where the extraction is done out of a single organism or a cell. Later, the bacteria in these samples were isolated in the lab with a medium that can nourish Lactobacillus. The researchers then separated the genomic material from these samples and amplified only the specific region of bacterial DNA. The analysis intended to also check for bacterial vaginosis and the entire set of proteins produced by these bacteria.
The study found that most Indian women harboured Lactobacillus as major bacterial species, indicating a healthy vagina. Apart from Lactobacillus, Halomonas, and Achromobacter were the other dominant bacterial family. Among Lactobacillus, they detected more than ten prominent species, including L. iners, L. crispatus, L. gasseri, and L. jensenii. Since these species have been associated with birth outcomes, they were chosen for further analysis.
In India, around 3.6 million infants each year are born before 37 weeks of pregnancy and suffer medical complications, including death. The findings of this study will throw insights into the role of microbes in birth outcomes. Analysing the bacteria present in the vagina of pregnant women can also help clinicians identify those who are at risk of delivering their baby prematurely. This data, in turn, could help future diagnostic and therapeutic approaches to help avert or delay premature birth.
"In the future, we plan to identify biomarkers for preterm delivery and develop a diagnostic tool for early prediction of any adverse birth outcome," concludes Dr Das.
This article has been run past the researchers, whose work is covered, to ensure accuracy.