A Lactobacillus-Deficient Vaginal Microbiota Dominates Postpartum Women in Rural Malawi

Abstract

The bacterial community found in the vagina is an important determinant of a woman's health and disease status. A healthy vaginal microbiota is associated with low species richness and a high proportion of one of a number of different Lactobacillus spp. When disrupted, the resulting abnormal vaginal microbiota is associated with a number of disease states and poor pregnancy outcomes. Studies up until now have concentrated on relatively small numbers of American and European populations that may not capture the full complexity of the community or adequately predict what constitutes a healthy microbiota in all populations. In this study, we sampled and characterized the vaginal microbiota found on vaginal swabs taken postpartum from a cohort of 1,107 women in rural Malawi. We found a population dominated by Gardnerella vaginalis and devoid of the most common vaginal Lactobacillus species, even if the vagina was sampled over a year postpartum. This Lactobacillus-deficient anaerobic community, commonly labeled community state type (CST) 4, could be subdivided into four further communities. A Lactobacillus iners-dominated vaginal microbiota became more common the longer after delivery the vagina was sampled, but G. vaginalis remained the dominant organism. These results outline the difficulty in all-encompassing definitions of what a healthy or abnormal postpartum vaginal microbiota is. Previous identification of community state types and associations among bacterial species, bacterial vaginosis, and adverse birth outcomes may not represent the complex heterogeneity of the microbiota present. (This study has been registered at ClinicalTrials.gov as NCT01239693.)IMPORTANCE A bacterial community in the vaginal tract is dominated by a small number of Lactobacillus species, and when not present there is an increased incidence of inflammatory conditions and adverse birth outcomes. A switch to a vaginal bacterial community lacking in Lactobacillus species is common after pregnancy. In this study, we characterized the postpartum vaginal bacterial community of a large group of women from a resource-poor, undersampled population in rural Malawi. The majority of women were found to have a Lactobacillus-deficient community, and even when sampled a year after delivery the majority of women still did not have Lactobacillus present in their vaginal microbiota. The effect of becoming pregnant again for those who do not revert to a Lactobacillus-dominant community is unknown, and this could suggest that not all Lactobacillus-deficient community structures are adverse. A better understanding of this complex community state type is needed.

Structure of Vaginal Microbiome Community After Perineal Disinfection and Its Effects on Neonatal Oral Microbiome

“…Additionly, the results showed that most samples during pregnancy belonged to CST III and CST VI, dominated with Lactobacillus spp. While after disinfection, the majority of CST III and CST VI during pregnancy switched to CST IV, in concordance with previous studies (Doyle et al, 2018;MacIntyre et al, 2015;DiGiulio et al, 2015). Increased rate of CST IV was also reported in neonatal oral samples.…”

Changes in key vaginal bacteria among postpartum African women initiating intramuscular depot-medroxyprogesterone acetate

“…and during pregnancy [43,44]. This time also coincides with a known period of higher HIV risk in women [45].…”

“…Our study may also be limited in generalizability due to the source population of our participants. Postpartum, amenorrheic women were enrolled to reduce the variability of the vaginal microbiome due to the menstrual cycle [9,17,33], however vaginal microbiota in the postpartum period may differ from vaginal microbiota found in menstruating women of childbearing age [43,44]. Lastly, the use of a qPCR, a targeted approach, might have missed changes in PLOS ONE important bacterial taxa not assessed, including taxa associated with an optimal vaginal microbiota.…”

Assessment of microbiota:host interactions at the vaginal mucosa interface

“…In contrast, carnitine, a product of lysine or methionine degradation involved in transport of long-chain fatty acids, is lower in vaginal mucosal samples isolated from BV patients while levels of the precursor, deoxycarnitine and ascorbic acid are higher [125]. Acyl-carnitines such as acetylcarnitine, propionylcarnitine, and butyrylcarnitine have also been previously reported to be lower in BV [22]. One proposed mechanism for lower carnitine levels in BV is through their conversion to trimethlyamine by BV associated bacteria [125].…”

“…Following delivery, when maternal oestrogen levels fall, vaginal Lactobacillus spp. dominance decreases and there is a shift towards a high-diversity microbiota community structure [19] that can persist in some women for up to one year postpartum [21,22]. At menopause, reduced oestrogen levels are associated with decreased vaginal epithelial glycogen deposition, depletion of Lactobacillus spp.…”