Influence of Vaginal Microbiota on Sexual and Reproductive Health: A Mini Review

INTRODUCTION

Human development and defenses as a whole are significantly influenced by microbiota. The macroscopic host and its commensal symbiotic bacteria are both multicellular beings that exist as meta-organisms [1]. Viruses, fungi, bacteria, protozoa, and other microbial species are present in these complex microbial communities [2, 3]. These symbionts are crucial in regulating the majority of host physiology due to their exceptional enzymatic capabilities and potential to express ten times as many different genes as their host's genome [4]. The human microbiota encompasses the communities of microorganisms that reside in the human body and the microbiome represents the genetic profile of all such microorganisms taken collectively [5-7]. The complex symbiotic, commensal, and pathogenic microbial association that lives in and colonizes the human body is essentially represented by a component of the cumulative genome of the human species [8]. The human microbiome, which is made up of about 10,000 different species of bacteria, lives inside the human body, similar to how the mouth and gut each have a variety of unique microbial populations. Additionally, trillions of tiny microorganisms, such as fungi, viruses, and bacteria, live in the female vagina [9]. This review's goal is to give a thorough explanation of the vaginal microbiome. The characteristics of bacterial vaginosis (BV) are reviewed about female health, and a strong correlation between BV and many illnesses is characterized by the need for thorough, accurate, and state-of-the-art treatment that lowers the negative effects on health (Figure 1).

Vaginal microbiota- introduction

In 1892, German obstetrician and gynecologist, Albert Doderlein discovered a long, thick, motile, rod-shaped, gram-positive, non-spore-producing microorganism in the vaginal fluid, which led to the discovery of vaginal microbiota [10]. When this bacterium was first identified, it was known as Doderlein's bacillus; however, because of its capacity to make lactic acid, it was later renamed Lactobacillus. Doderlein also found that the absence of Doderlein's bacillus in the vaginal fluid was linked to puerperal fever and that Doderlein's bacillus had an antagonistic effect on Staphylococcus growth [11, 12]. These key discoveries laid the groundwork that Lactobacillus is the most common bacterium in the vagina and is essential for women's health. It is now commonly acknowledged that the vaginal microbiome is more diverse and active than previously thought as a result of the advent and rapid development of high-throughput sequencing technologies [13]. A non-Lactobacillus dominant vaginal microbiome has also been linked to several diseases, including STIs, gynecologic cancer, infertility, and preterm birth, according to several observational studies [14].

Microbial communities of vaginal microbiota

The vaginal microbiome is a complex and dynamic micro-ecosystem that continuously changes throughout a woman's whole life and during her menstrual cycle. A stratified squamous non-keratinized epithelium and cervicovaginal secretion make up the vaginal mucosa [15]. Understanding the nature of the human body requires a study of the human microbiome, which will help researchers to establish whether the microbial communities in humans are uniform across the board or vary from person to person. Variations in the core microbiota have been suggested to be associated with changes in human health and the likelihood of contracting illnesses [16]. Bacteria are one of the many varieties of microbes that exist and are responsible for a major portion of all life on Earth. According to the thorough study of the human vaginal microbial community, the Lactobacillus bacterial species predominate in the vaginal composition in the majority of females. This particular group of bacteria acts as protective agents in the reproductive system, preventing the colonization of hazardous germs by releasing hydrogen peroxide and some other compounds, such as bacteriocins. Although they contain a diverse range of both strictly and facultative anaerobic bacteria, a sizable portion of asymptomatic and healthy women lack enough Lactobacillus sp. in their vaginal microbiota. As a consequence, it can be said that the human vagina contains many core microbiomes rather than just a single core microbiome [17, 18]. Moreover, one of the essential aspects influencing vaginal composition is ethnicity. Asian and Caucasian women have been shown to have much greater lactobacilli levels than Black and Hispanic women [19, 20]. However, it is yet unknown whether this variation in Lactobacilli levels is a result of genetic determinants or associated with various hygiene practices, particularly vaginal douching [21].

Researchers demonstrated that there exist five distinct classified microbial communities, or five different forms of Community State Types (CST), especially I, II, III, IV, and V as it is shown in Figure 2. Since no two females have the same vaginal environment, I assume it depends on which species of Lactobacillus plays a cent in these communities. Lactobacillus crispatus (L. crispatus) represents Community State Type I (CST I), L. gasseri leads Community State Type II (CST II), L. iners controls Community State Type III (CST III), and L. jensenli dominates Community State Type V (CST V). Although Community State Type IV (CST IV) lacks Lactobacillus sp., it is incredibly rich in BV-associated strictly anaerobic bacteria such as Megasphera, Prevotella, Gardenella, and Sneathia [22].