BACTERIAL VAGINOSIS: MODERN VIEW ON THE PROBLEM
Bacterial vaginosis (BV) is one of the most common infectious pathologies of women of childbearing age. Bacterial vaginosis is a condition in which the normal microflora of the vagina, represented mainly by lactic acid bacteria, is replaced by numerous anaerobic and other conditionally pathogenic flora. The connection of dysbacteriosis with such complications as rupture of the fetal membranes, premature labor, infections of the chorion, amnion, amniotic fluid, fetal fetal death was established. This suggests the need for screening of bacterial vaginosis and its treatment before pregnancy.
The normal microflora of the vagina of a woman of reproductive age contains gram-positive and gram-negative aerobic, facultative-aerobic, and obligate anaerobic microorganisms, with 95–98% of all microorganisms represented by lactic acid bacteria, among which 96% are H2O2-producing strains. Even genital mycoplasmas with a titer of < 104 CFU / ml and fungi of the Candida genus in an amount not exceeding 103 CFU / ml are referred to the normal vaginal microflora. According to some reports, Atopobium vaginae is also a representative of normal flora, but this microorganism is not well understood and is more common in women with bacterial vaginosis.
In turn, the microflora of pregnant women differs from that in non-pregnant women of fertile age. There is a significant predominance of L. vaginalis, L. crispatus, L. gasseri and L. Jensenii and a decrease in the number of other microorganisms. Also, the microflora of the vagina of pregnant women is more stable and resistant.
In the process of evolution, mechanisms of biological protection of the genital organs were formed to the possible effects of various pathogenic factors, including infectious agents. These include: a closed state of the genital slit, a local independent system for the production of antibodies against certain bacteria of the cervix, the acidic environment of the vagina. Lactobacilli are involved in the formation of an environmental barrier, providing colonization resistance, produce H2O2, lysozyme, and bactericins, but the main mechanism is their ability to form acid. Lactic acid is formed as a result of the destruction of glycogen epi- telium, determines the acid reaction (pH < 4.5) and is a powerful microbicide under such conditions that can prevent the development of urogenital infection
EPIDEMIOLOGY AND ETIOLOGY BV
Bacterial vaginosis (BV), according to various sources, affects about 30% of women. Among pregnant women, the prevalence of BV is from 15 to 46%. The risk factors for BV formation include smoking, low social status, treatment with antibiotics, and erratic sex. At the same time, girls in the puberty period and postmenopausal women (after 50 years) rarely get sick with bacterial vaginosis, which confirms the great importance of hormonal factors in its origin.
Etiological factors most often are Gardnerella vaginalis and Prevotella, Peptostreptococcus and Bacteroides spp. The main importance in the development of BV for a long time attached G. vaginalis, allocated in 92% of cases from the lower genital tract. However, the virulent strains of G. vaginalis and the mechanism of development of BV are still to be determined. A number of authors are of the opinion that G. vaginalis, causing inflammation, creates conditions for the distribution of obligate anaerobes. In addition, in the last 10 years, new microorganisms, Atopobium vaginae, which are more specific for BV than G. vaginalis, as well as Leptotrichia, Megasphaera, previously unknown species of the genus Clostridium, have been identified by PCR. The absence of an animal model of G. vaginalis-associated infection is also a cause of development of the disease. It is believed that BV may develop against the background of a decrease in local immunity, changes in the properties of lactobacilli (prevalence of lactobacillus strains that do not produce H2O2) and for a number of other reasons. Today, most researchers agree that BV is a polyetiological disease.
The classic symptom of BV is the smell, described as fishy. This is due to the production of amines (including trimethylamine, putrescine and cadaverine) by anaerobic bacteria. As the pH rises, the amines evaporate more strongly, and in this regard, patients note an increase in odor when the medium is alkalized, for example, after sexual intercourse, during menstruation. A large amount of vaginal discharge is the most frequent, but less specific symptom. Fish smell, vaginal discharge are found in 70–90% of patients with BV, but the same symptoms were observed in 57% of women without BV, which indicates their non-specificity. An important factor is the presence in 45% of BV patients of complaints of irritation symptoms (burning, itching, pain), which is more characteristic of vaginitis and can be misleading regarding the diagnosis. Thus, to confirm the diagnosis, it is necessary to conduct additional studies. Moreover, routine screening studies have shown that BV is asymptomatic in 50% of cases.
The main method of clinical diagnosis is the Amsel method. A diagnosis of BV can be made on the basis of 3 of 4 criteria proposed by R. Amsel: 1) an increase in the pH of the vaginal disposable> 4.5; 2) the pathological nature of vaginal discharge; 3) positive amine test (fishy smell); 4) identification of key cells by microscopic examination of unstained and Gram-stained smears. To identify these criteria, there are express tests: FemExam (trimethylamine study and pH measurement), gloves for measuring the pH of the patient herself, BVBlue (measuring sialidase activity), Pip Activity TestCard (measuring proline aminopeptidase activity).
In the scientific community, the microbiological method is considered preferable, since about 50% of BV are asymptomatic. Microbiological diagnostics is based on Gram smears and is evaluated on the Nugent scale, which reflects the prevailing flora: normal (0–3 points), intermediate (4–6 points) and BV (7–10 points). The laboratory methods also include the Ayson – Hay method, a method based on WHO criteria, and the PCR method. The method based on PCR makes it possible to determine the qualitative and quantitative composition of microflora in real time. It has high sensitivity and specificity, it allows to identify anaerobic flora, and in particular Atopobium vaginae, whose role in the development of BV is actively debated.
One of the main problems of patients with BV is increasing susceptibility to other STIs. Studies have shown a link between BV and HIV. In the absence of lactobacteria in the vaginal microflora, the risk of acquiring HIV infection increases by 2–3.7 times, the risk of infection gonorrhea - 1.7 times, susceptibility to the herpes virus type II increases 2.1 times. Therapy with metronidazole reduces the risk of chlamydial infection, but not other STIs.
When BV increases the risk of infection after surgery on the pelvic organs. Thus, it was shown that inflammatory diseases of the pelvic organs complicated the postoperative period in 11.2% of women who received placebo for concomitant BV. Taking metronidazole for 10 days in the same situation reduced the number of PID to 3.8%.
Among women who took metronidazole or placebo for 10 days before surgery, 3.8% of women from the group that took metronidazole were found, compared with 11.2% of the placebo group. Other studies have shown a 5.6-fold increase in the risk of developing infectious complications in determining key cells in vaginal smears before surgery.
BV is associated with a 6-fold increase in the risk of postpartum endometritis after a cesarean section. The use of metronidazole reduces the risk of postoperative endometritis in women with or without BV.
The microflora of pregnant women differs from that in non-pregnant women of fertile age. There is a significant predominance of L. vaginalis, L. crispatus, L. gasseri and L. Jensenii and a decrease in the number of other microorganisms. Also, the vaginal microflora of pregnant women is more stable and resistant.
BV increases the risk of community-acquired inflammatory diseases of the pelvic organs, chronic endometritis, and may be the cause of abnormal uterine bleeding, cystitis.
Many studies have found a link between BV during pregnancy and its adverse outcomes (preterm delivery, low birth weight, premature rupture of the membranes, postpartum endometritis, intra-amniotic infection). Unfortunately, treatment of BV during pregnancy was not effective in preventing these adverse outcomes. Management of patients with BV remains an important issue and is likely to be resolved only with the establishment of exact pathogenesis mechanisms. The study of genetic factors affecting the development of complications of BV has given certain results. For example, the rarer of 2 alleles of polymorphism in the promoter of tumor necrosis factor α is associated with an increased risk of premature birth. In women with this allele and BV, the risk of developing preterm birth is 2–2.5 times higher. At the moment there are no clear recommendations for the treatment of BV during pregnancy, except for the use of metronidazole, which promotes regression of symptoms of BV.
Prebiotic correction with Bacterial Vaginosis
The increased interest in the vaginal microecosystem is largely due to the fact that the role of the evolving microbial populations of this biotope is not only to maintain vaginal colonization resistance, but also to form the microecological health of the newborn, and therefore, the human population as a whole.
The formation of the qualitative and quantitative composition of microflora is governed by the complex mechanism of intermicrobial interactions within each microecosystem, and is also controlled by the physiological factors of the host organism in the dynamics of its life.
An important component of the vaginal indigenous flora are lactobacilli, bifidobacteria and propionic acid bacteria.
The evolution of the vaginal biotope has led to the development of adaptive mechanisms that allow these microorganisms to actively develop in the vaginal environment and adhere to the epithelium, forming strong symbiotic ties with it, and successfully compete with facultative and transient conditionally pathogenic and pathogenic microflora.
The main place among indigenous vaginal bacteria is occupied by the genus Lactobacillus (L.). Among the lactobacilli most commonly distinguished L. fermentum, L. acidophilus, L. casei, L. plantarum, L. brevis. Due to the ability to actively proliferate in the vaginal environment, adhese on the surface of epithelial cells, ferment glycogen with the accumulation of organic acids, synthesize hydrogen hydrogen, lysozyme, bacteriocins, stimulate local immunity, lactobacilli are most adapted to the vaginal colonization and protection from colonization. conditionally pathogenic microorganisms. This is evidenced by their high concentration in the vaginal secret of healthy women (up to 109 CFU / ml).
In the vaginal ecosystem of bifidobacteria, Bifidobacterium (B.) bifidum, B. longum, B. infantis, B. breve, B. adolescentis are most often found.
Vaginal bifidobacteria, like lactobacilli, are able to ferment glycogen to form organic acids, adhere to the surface of the epithelium, synthesize antimicrobial metabolites, stimulate local immunity. They effectively inhibit the growth of gardnerellas, staphylococci, Escherichia, Klebsiell, fungi and other opportunistic microorganisms. In healthy women, bifidobacteria are found in lower concentrations than lactobacilli (up to 107 CFU / ml), but during pregnancy, and especially in the prenatal period, their population level increases dramatically as a powerful factor in protecting the body of the newborn from colonization by potential pathogens. Pro-pionic acid bacteria present in the vaginal biotope are gram-positive, asporogenic, polymorphic small rods, differing in their strict anaerobiosis. They actively ferment glycogen with the formation of propionic and acetic acid, which suppress the growth of opportunistic bacteria and fungi.
In addition, propionic acid bacteria have antioxidant, antimutagenic, anticarcinogenic, and immunostimulating properties.
Vaginal lactobacilli are able to synthesize hydrogen peroxide, which suppresses the growth of obligate anaerobes of the genus Mobiluncus, Bacteroides, Peptococcus, Pepto-streptococcus, Clostridium, and others. inhibited microorganisms significantly increases and spreads to many optional anaerobic and aerobic microorganisms (Gardnerella (G.) vaginalis, Staphycoccus aureus, Escherichia colli, Pseudomonas ssp., Canda albicans, etc.). An important protective factor of the vaginal indigenous microflora is its ability to synthesize lysozyme and bacteriocins.
Bacterial vaginosis (BV) is currently considered to be a synergistic polymicrobial syndrome, which is characterized by a decrease in concentration or the complete absence of predominantly peroxide-producing lactobacilli and intensive growth of obligate and facultative anaerobic opportunistic microorganisms (in 100–1,000 times the normal level). BV according to modern concepts is defined as the dysbiotic state of the vaginal biotope.
It is not possible to determine the true frequency of occurrence of BV due to the fact that it is not statistically recorded, and because in 1/2 women this condition is asymptomatic. However, the second half of patients with BV is the most common group of women who come to the gynecologist with complaints of unusual discharge from the genital tract. In outpatient gynecological practice, BV is detected in 15–19% of patients, among pregnant women it is found in 10–30% of cases, and in women with inflammatory diseases of the pelvic organs (PID) - in 35%.
Complications of BV can be dangerous: the development of chorionamnionitis, premature labor, premature rupture of amniotic fluid (increases 2.6–3.8 times), endometritis, postpartum sepsis, pericultitis, co-factor in the development of human papillomavirus infection, activation of latent viral infection (low redox potential and hypoxia of the vaginal tissues at high pH), conditions for colonization of the urogenital organs by sexually transmitted infections (STIs), in 32% of BV occurs in tubal infertility, in 35%PID It has also been proven that BV is a risk factor for infection with IDI1 and HIV infection.
The emergence of nucleic acid amplification methods made it possible to take a fresh look at the problem of BV, since it became possible to identify microorganisms that are very difficult to cultivate
The nature of BV is polymicrobial. In our observations, the species and quantitative composition of the vaginal microflora of patients with BV looked as follows: Lactobacillus spp. 0–11% (up to 104), G. Vaginalis 90–100% (107–109), Mobiluncus spp. 8–35 and up to 50% (1010 and more), PeptoStreptococcus spp. 29–95% (105 and more), Prevotella spp. up to 80% (105 and more), Bacteroides spp. 53–97% (105 and more), Fusobacterium spp. 30% (104 and more), E. сoli 15–25% (more than 104), Staphylococcus spp. 45–65% (more than 105), Streptococcus spp. 5–25% (up to 104), M. hominis 50–80% (104 and more), U. urealyticum 10–30% (104 and more).
The emergence of nucleic acid amplification methods made it possible to take a new look at the problem of BV, since it became possible to identify microorganisms that are very poorly cultivated. The achievements of molecular biology associated with the development of the polymerase chain reaction method have provided new opportunities for studying human microflora. In addition to the qualitative identification of STI pathogens, accurate quantitative assessment of microflora has become possible.
In studies D.N. Fredricks (2005) and Srinivasan Sujatha, D.N. Fredricks (2008) identified several other microorganisms involved in the formation of BV: Sneathia sanguinegens, Porphyromonas asaccharolytica, Megasphera sp., Atopobium vaginae, Clostridium phylum, Leptotrichia.
The development of BV mainly causes alkalization of the environment and reduction of colonization resistance of the indigenous microflora. The colonization properties of the indigenous flora are most dependent on its adhesive properties. Attaching epithelial cells to the surface and the formation on the mucous membrane of the vagina of a biofilm consisting of vaginal mucus, colonies of the indigenous microflora and its metabolites are powerful protective factors that prevent adhesion and excessive development of opportunistic microorganisms, as well as the penetration of their cells and metabolic products beyond the vaginal biotope.
It is important to take into account that not only the indigenous microflora, but practically all bacteria and unicellular fungi in the human body during reproduction form communities protected from the environment by additional shells. All described types of communities have a number of common properties, of which the isolation of a community containing the extracellular membrane and the accumulation of the extracellular matrix can be considered the main ones. In such communities, bacteria exhibit differentiation of characters, as a result of which they are in different states. At the same time, a significant part has a reduced metabolic activity. Microbes within communities are in contact with each other in different planes, have a minimal free surface for contact with the matrix. A number of microcolonies and similar isolated communities are combined with a special matrix into a common structure, called biofilm.
Biofilms provide the bacteria within them with a significant increase in survival in the presence of aggressive substances and antimicrobial agents, which must be taken into account in the determination of the management and treatment of patients. Moreover, the formation of communities and biofilms results in the survival of bacteria in the presence of antibiotics in quantities 500–1,000 times greater than the overwhelming concentration of drugs, which is taken into account when developing drugs in modern conditions. In bacteriological laboratories in various countries, antibiotics are already being evaluated on the effectiveness of their action, not only for isolated microorganisms, but also for those contained in biofilms.
With the pathological development of pathogenic microorganisms, the formation of various biofilms also occurs. Bacteria from this film are periodically released and migrate, contributing to the spread of infection, causing the patient to deteriorate. Microorganisms in communities are virtually inaccessible to the factors of the immune defense of both cells and antibodies. The use of antibiotics in ordinary and even higher doses is insufficient or ineffective because the drugs do not penetrate into the biofilm in a concentration that can cope with the microorganisms contained in it. The survival of bacteria in the composition of biofilms significantly affects the effectiveness of therapy.
For the treatment of the mild form of BV, only 6 days of ascorbic acid use are sufficient, and for severe forms it is possible to associate it with the drugs metronidazole and clindamycin.
Therefore, there are still a number of problems associated with treatment of BV, the main one being the frequency of relapses, reaching 40–70% in the next 3–6 months. with standard treatment. The presence of a biofilm (biofilm) in BV can be crucial in the pathogenesis of this disease. Fredricks D.N. et al. (2005) demonstrated the presence of bacterial biofilm in 90% of patients with BV, whereas in the absence of BV only in 10%. Biofilms were tightly attached to the surface of the epithelium of the vagina and contained specific groups of bacteria (mainly G. vaginalis — up to 60–90% of the mass of the biofilm and Atopobium vaginae).
Biofilms in BV have a high degree of organization, are tightly attached to the surface of the epithelium of the vagina. The concentration of some microorganisms in a biofilm can reach up to 1011.
Such a biofilm is resistant to metronidazole (the main standard drug), protects against its action on gardnerella, which also turns out to be stable. In the treatment of BV with clindamycin (the second standard preparation), there is a sharp inhibition of lactobacilli and other physiological flora, and in their absence in 3–4 months. growth of conditionally pathogenic microorganisms and a new relapse of the disease are observed again. In addition, a number of researchers caution against prescribing clindamycin in the first episode of BV, since anaerobic flora more quickly forms resistance to clindamycin than to metronidazole. However, biofilms are destroyed much faster at low pH.
Recently, an option has appeared to optimize the treatment of BV and ensure the prevention of further relapses using prebiotics. When using the term “prebiotics”, substances are meant that create the conditions for maintaining protective microflora. One of them is ascorbic acid. The idea is simple - ascorbic acid lowers the pH of the vagina, thereby destroying biofilms, inhibits the growth of bacteria that cannot reproduce at a pH of 4.3 and below (G. vaginalis is not genetically adapted to live in an acidic environment, it lacks the ArsR gene, responsible for adaptability to acidic pH). At the same time, lactobacilli can multiply at pH values of 4.3 and below. Thus, with a decrease in the pH of the vagina for several days, there is a pronounced suppression of the growth of anaerobic bacteria, as well as the restoration of normal flora (L. acidophilus, L. gas-seri). In addition, ascorbic acid, mixing with H2O in the vagina, promotes the production of hydrogen peroxide, an endogenous bactericidal substrate. The drug begins to work after 2 hours, reliably relieving the woman from the symptoms of BV.
For the treatment of the mild form of BV, only 6 days of ascorbic acid use are sufficient, and for severe forms it is possible to associate it with the drugs metronidazole and clindamycin. When oral use of ornidazole or clindamycin, it is advisable to administer ascorbic acid simultaneously with systemic antibacterial therapy. For example: ascorbic acid - 1 vaginal tablet at night on the day of initiation of therapy, then for 5 days: ornidazole 0.5 1 tablet 2 p / day + ascorbic acid in the vagina at night.
When using vaginal forms of metronidazole and clindamycin, it is advisable to use ascorbic acid during and after their use: ascorbic acid 1 tablet in the morning in the vagina, vaginal form of metronidazole or clindamycin at night 6 days + 6 nights of ascorbic acid after course of treatment.
Repeated courses of therapy increase the effectiveness of treatment. If necessary, ascorbic acid can be applied for a long time, daily for several weeks or even months. There are no restrictions on the duration of the drug use. Interruptions in the use of ascorbic acid due to inter-cyclical or menstrual bleeding are not necessary; Various diseases or infectious diseases are also not contraindications to its use. The drug is not contraindicated during pregnancy and lactation.