The vagina is an open cavity and is one of the most important microecological zones in the body. Under normal conditions, it is a microecological system mainly composed of dominant bacteria such as Lactobacillus. Vaginal micro-ecological balance is an important factor in maintaining the health of the female reproductive tract, and any micro-ecological imbalance or dysbiosis may lead to reproductive tract infections and other diseases.
What is the vaginal micro-ecosystem?
The female vagina is a complex microecological system that hosts more than 50 microorganisms that reside mainly in the folds of the mucosa surrounding the vagina, followed by the vault and partly in the cervix. The main resident bacteria in the vaginal flora are Lactobacillus, Staphylococcus epidermidis, Escherichia coli, Corynebacterium, Group B Streptococcus, Enterococcus faecalis, Mycoplasma, Pseudomonas, Peptococcus and Bacteroidetes, etc. Lactobacillus is the main resident bacteria in the vagina, accounting for more than 90% of the resident vaginal bacteria.
II. Role of vaginal microecological balance
The normal vaginal flora maintains a harmonious and dynamic balance with the host and environment, i.e. vaginal micro-ecological balance, which can play the following roles.
①Bio-barrier effect: the normal flora, which are planted in the epithelium of vaginal mucosa in a hierarchical and orderly way, are like a biofilm, which not only plays a protective role for the host, but also directly affects the colonization force, so that other pathogenic bacteria are not easy to adhere to the epithelium of vaginal mucosa.
②Maintain acidic environment: As mentioned before, Lactobacillus breaks down glycogen in the exfoliated epithelium into lactic acid, which makes the vaginal environment weakly acidic and helps to inhibit the growth of many microorganisms, while maintaining the vaginal self-cleaning effect.
③Immunity: like other parts of the normal flora, it has an effect on the formation of humoral and cellular immunity of the host, which helps to defend against the invasion of pathogenic bacteria.
Factors affecting vaginal microecology
1. Estrogen level
Estrogen binds to estrogen receptors on the surface of vaginal epithelial cells and initiates a series of physiological activities of epithelial cells, including the production of glycogen. Because estrogen levels are constantly changing throughout a woman’s life, vaginal flora varies among women at different ages. There are also changes in estrogen during a woman’s menstrual cycle, and thus changes in vaginal flora can occur accordingly.
2. Sexual life
Sex also has an effect on the vaginal environment, as semen is weakly alkaline and vaginal pH does not return to normal within 8 hours after sex. At the same time, sexual intercourse may spread diseases such as gonococcus, chlamydia, human mycoplasma and mycoplasma solium, which can be brought into the vagina by sexual intercourse and produce corresponding infections. In addition, the use of contraceptive devices (condoms, uterine caps, vaginal diaphragms, vaginal rubber bands, intrauterine devices, etc.) can also affect the vaginal micro-ecological balance.
3. Other
Reproductive tract surgery, drugs (systemic or local antibiotics, immunosuppressants, etc.) tend to change the vaginal environment, and systemic diseases, such as anemia, hypothyroidism, systemic or local infections, are also factors that affect the vaginal microecological balance. In addition, personal life and hygiene behaviors, menstrual hygiene products, and socioeconomic status can also have an impact on the vaginal environment.
Vaginal micro-ecological imbalance (dysbiosis)
1. Vulvovaginal pseudomonal yeast disease
Pseudomonas aeruginosa resides in the vagina of normal women. Under normal circumstances, it is symbiotic with the organism and does not cause disease, among which Pseudomonas albicans is the most common. Once the equilibrium in the vaginal microenvironment is disturbed, Pseudomonas albicans changes from the yeast phase to the mycelial phase and grows and multiplies in the vagina, causing vulvovaginal pseudomonal yeast disease.
The clinical manifestations of Pseudomonas vaginalis are mainly itching and burning pain in the vulva, which is heavier at night, and may be accompanied by painful intercourse and burning sensation during urination. Gynecological examination reveals a white, thick, bean curd-like or even lumpy discharge and congested and edematous vulvovaginal mucosa. The diagnosis can be confirmed by microscopic examination of the discharge and finding the budding cells and pseudomycorrhizae of Pseudomonas albicans. It is mainly treated with antifungal therapy, but is prone to recurrence or repeated infections.
2. Bacterial vaginosis
Bacterial vaginosis is caused by a combination of multiple bacterial infections. The number of lactobacilli in the vagina decreases or is absent, while the number of other vaginal microflora increases and the dominance of lactobacilli is replaced by Gardnerella and mixed anaerobic flora.
The clinical manifestations of bacterial vaginosis include increased leucorrhea with an odor, and in some patients, itching and burning of the vulva. Examination reveals a lot of milky white homogeneous vaginal discharge without inflammatory manifestations such as congestion of the vaginal mucosa. The following four diagnostic criteria for bacterial vaginosis are more widely used.
① thin homogeneous vaginal discharge;
② odor of the discharge (positive ammonia odor test);
(iii) Vaginal pH greater than 4.5;
③Vaginal pH is more than 4.5; ④Vaginal discharge smear with clue cells. Bacterial vaginosis can be diagnosed if three of the four tests are positive. The main treatment is anti-anaerobic treatment.
3. Trichomonas vaginitis
Trichomoniasis is a sexually transmitted disease with a high incidence and is a common vaginitis. Trichomonas infection is closely related to the environment in the vagina. The most suitable pH for Trichomonas vaginalis is 5.2-6.6. Lactobacillus is the main flora in the vagina of healthy women, which keeps the vaginal pH weakly acidic and inhibits Trichomonas growth. When the vaginal environment is imbalanced, the pH of the vagina increases, making it easier for Trichomonas to reproduce in the glands or vaginal folds. Trichomonas consumes glycogen in the vaginal epithelium, which reduces the lactic acid produced by lactobacillus enzymes, making the pH of the vagina alkaline and favoring the growth of Trichomonas and other pathogenic bacteria, thus aggravating the imbalance in the vaginal microenvironment.
The clinical manifestations of trichomoniasis are mainly increased leucorrhea, milky white or yellowish green, sometimes purulent, often frothy, with a foul odor, followed by vulvar pruritus, notable at the vaginal opening and vulva, accompanied by a burning sensation and painful intercourse. The diagnosis is confirmed by microscopic examination of the secretions and finding Trichomonas vaginalis. The main treatment is antitrichomonas therapy.
Vaginitis caused by vaginal microecological imbalance has a high incidence and can recur, and is a gynecological inflammatory disease that endangers women’s reproductive health and causes problems for women. To get rid of the disease it is important to re-establish a healthy micro-ecology in addition to treating the causative organisms. It is necessary to remove the causative factors, establish good lifestyle habits and sexual hygiene, avoid abuse of antibiotics and immunosuppressants, etc.