Dynamics of the Vaginal Microflora during the Menstrual Cycle of HIV-positive and HIV-negative Women in a Sub-urban Community in Kenya

Document Type

Book Chapter

ISBN

978-93-49970-28-1

Publication (Name of Journal)

Research Perspective on Biological Science

Department

Obstetrics and Gynaecology (East Africa); Centre of Excellence in Women and Child Health

DOI

https://doi.org/10.9734/bpi/rpbs/v4/1438

Publisher

BP International

Abstract

Introduction: Normal vaginal microflora is usually dominated by Lactobacillus species, which play an important role in the maintenance of vaginal health. The dynamism of the vaginal microflora is especially notable as changes that occur during menses. The vaginal micro-environment is dynamic and undergoes changes during the menstrual cycle in women of reproductive age. These changes correlate with the accompanying hormonal changes. Indeed, the vagina is a highly dynamic ecosystem. Studies show that changes occur in the vaginal microflora during the normal menstrual cycle.

The recurrent imbalance that occurs in the equilibrium of vaginal microflora favors the overgrowth of bacterial vaginosis (BV)-associated bacteria. The relative depletion of the resident Lactobacilli has been shown to be most profound at the time of menses, indicating that the vaginal microflora become less stable during this event. This phenomenon has generally been attributed to the premenstrual decline in circulating levels of estrogen, which in turn affects the colonisation strength of the vaginal Lactobacilli, for example by limiting their capacity for epithelial adherence. The vaginal Lactobacillus microflora are probably further challenged by the menstrual flooding of the vagina, which is accompanied by a sharply rising pH, further exacerbating the unfavorable conditions for epithelial adherence of the Lactobacilli. Under such conditions, the colonisation resistance offered to BV-associated anaerobes can easily be overcome. Menses possibly also induces a wash-out of Lactobacilli through haemagglutination. These mechanisms might explain why BV is less prevalent in pregnant and postmenopausal women, despite the relative estrogen deficiency, especially in the latter group. To further demonstrate the important role that hormones might play in maintaining the balance in the vaginal ecosystem, a recent longitudinal study found women using hormonal contraceptives to have less prevalence due to greater remission of BV. The objective of this study was to characterize and explore the changes in the vaginal microflora during the menstrual cycle of HIV positive (HIV+) and HIV negative (HIV-) women in a sub-urban population of Kenya.

Methods: In a longitudinal study of 38 premenopausal women, 20 HIV+ and 18 HIV-, high vaginal swabs were taken for genomic DNA extraction. Gram stains were prepared at each of the six visits for each woman. Nugent scores were performed, and quantification of three Lactobacillus spp. (L. crispatus, L. jensenii and L. iners) and Gardnerella vaginalis and Atopobium vaginae carried out by real-time or quantitative PCR (qPCR) technique.

Results: Results based on Gram stain category showed a high concentration of L. iners in the normal vaginal microflora. This increases during bacterial vaginosis (BV). There were high levels of L. jensenii in half of the women with BV, while L. Crispatus was absent in BV cases. Concentration of G. vaginalis increased progressively from normal to BV microflora while A. vaginae was absent in normal microflora but was detectable in intermediate gram stain and increased progressively during the BV phase.

Analysis based on HIV status showed a high concentration of L. iners and G. vaginalis in both the HIV+ and HIV- groups. Condom use was significantly higher in HIV+ women, but the number of those harbouring the protective L. crispatus was less than in the HIV- group. The concentration of L. crispatus was remarkably lower in the HIV+ group. Atopobium vaginae was present in both groups but L. jensenii was not detectable in the HIV+ women.

Based on the phase of the menstrual cycle, analysis showed a high concentration of L. iners and G. vaginalis throughout the cycle. Concentration of L. crispatus increased while concentration of A. vaginae decreased throughout the menstrual cycle. At the initial phase of the menstrual cycle, L. jensenii was comparatively low and not detectable thereafter.

Conclusions: The predominant species in normal vaginal microflora in this Kenyan population of women is L. iners, and which increased during BV. Both HIV+ and HIV- groups had high concentrations of L. iners and G. vaginalis. Throughout the menstrual cycle, concentration of L. crispatus increased while concentration of A. vaginae decreased. At the initial phase of the menstrual cycle, L. jensenii was comparatively low and not detectable thereafter.

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