How to diagnose bacterial vaginosis

Bacterial vaginosis is a clinical syndrome of vaginal discomfort caused by the replacement of vaginal lactobacilli by another group of anaerobic bacteria (such as vaginal Gardnerella, Bacteroides, etc.), which is often ignored by people. In recent years, domestic scholars have found that various gynecological surgeries, pelvic inflammatory diseases and pregnancy complications are related, and can lead to acute salpingitis. Therefore, it should be taken seriously. There are several methods for laboratory examination of bacterial vaginosis.

1Amsel's gold standard method (also known as clinical routine examination method)

That is, three of the following four items must be met before diagnosis: vaginal pH>4.5; according to the results of some experts' research, women with normal vaginal flora also have increased vaginal pH after sexual intercourse or during menstruation, and cervical mucus mixed in vaginal secretions will also produce a higher pH. The vaginal pH of BV patients is greater than 4.5. Therefore, pH>4.5 is an indicator of BV; vaginal secretions increase, become thinner and milky, and have a peculiar smell; amine test is positive, that is, KOH is added to the secretions to produce a fishy smell; clue cell examination, this examination can also be done clinically or sent to the laboratory for examination. The specific operation is: take the secretions for saline wet mounts, and see scattered epithelial cells and bacteria between them. There are many bacteria on the surface of epithelial cells, making their edges jagged and unclear, forming so-called clue cells. If methylene blue saline is used as a wet mount, the bacteria will be stained dark blue, which is easy to distinguish from lactobacilli. Lactobacilli will also adhere to epithelial cells in small amounts. In actual work, it is not easy to accurately implement the above standards. Some factors unrelated to infection can also lead to high vaginal pH or cause the secretions to have an odor. In particular, the diagnosis of clue cells can be affected by the quality of the microscopic observation equipment, sample collection and operator experience. When using the traditional Amsel's gold standard method, BV can be missed. Clue cell detection is the most specific single BV clinical test, but fragments and degenerated cells are sometimes mistaken for clue cells. Eschenach et al. pointed out that at least the presence of clue cells in the vaginal epithelium can be judged as a positive result.

2-Amine Test (Test Card or Test Strip)

Conventional amine tests have poor objectivity, low sensitivity, and are greatly affected by the olfactory function of the experimenter. With the advancement of technology, the current amine test is organically combined with a membrane coated with a color indicator to overcome the above disadvantages and make the results more objective and effective. The production of ammonia in this test is due to the synergistic production of several types of ammonia by vaginal Gardnerella and anaerobic bacteria rather than lactic acid. These ammonia are easily volatilized under high pH conditions to produce foul-smelling putrescine and cadaverine. Recently, it has been proposed that Bacillus motilus can provide a special decarboxylase that can convert the high concentration of trimethylamine oxide present in BV women into trimethylamine. Broad proposed that trimethylamine is the main substance of the fishy odor of BV. Polyamines cause the exfoliation of vaginal mucosal epithelial cells, resulting in abnormal vaginal secretions. Lin Ying (1993) reported that the microorganisms adhering to the exfoliated clue cells are mainly vaginal Gardnerella, followed by Bacillus motilus. The amine test method was first proposed by Pheifer et al. in 1978. When KOH is added to vaginal secretion samples from women with BV, BV pathogens can release volatile amines such as dibutylamine, pentamethylenediamine, and trimethylamine to produce an ammonia smell. Some women with BV have a stronger vaginal odor after sexual intercourse, which may be because the pH value of semen is higher, playing the same role as KOH to produce an ammonia smell. Putrescine is also present in semen, and women who are sensitive to odors but do not have BV will notice this odor, so false positives in amine tests can occur in women who have had sexual intercourse recently. This method is an auxiliary diagnostic test.

3 Sialidase and proline aminopeptidase methods

The mechanism of the sialidase method is: a small amount of anaerobic bacteria grows in the normal vagina, and the ratio of anaerobic bacteria to aerobic bacteria is 1:2 to 1:5. When suffering from BV, the ratio of anaerobic bacteria to aerobic bacteria is 200:1 to 1000:1, and the activity of sialidase is related to the number of anaerobic bacteria. The activity of sialidase in the vagina of normal people is extremely low, and it cannot be detected by the sialidase method. Therefore, the sialidase method does not change color during the determination. When suffering from BV, the sialidase activity is greatly increased, even up to 40 times the normal level, and changes color during the determination. Other studies have shown that the activity of proline aminopeptidase in vaginal secretions is significantly increased when infected with BV. The disadvantage of this detection method is that the activity of sialidase in tumor cells is enhanced, and genital tumors can lead to false positives; in addition, some bacteria and Trichomonas in the vagina also produce proline aminopeptidase, and infection with these organisms can also cause increased enzyme activity and lead to false positives.

4 Rapid staining technology for multiple examinations of gynecological leucorrhea smears

Based on the different morphological characteristics of pathogens in leucorrhea, a multifunctional dye is used to simultaneously perform multiple tests on a glass slide, including Trichomonas, Candida, Cibotium, Neisseria gonorrhoeae, Gardnerella, heterogeneous nuclear cells, and cancer cells. The method is simple, the staining time is short, the staining structure is clear, the morphology is standard, and the pathogen detection rate is high, which provides a reliable basis for clinical diagnosis. Its multi-purpose function reduces the inconvenience of handling multiple specimens in daily work. Clue cells are a large number of Gardnerella attached to the surface of vaginal exfoliated squamous epithelial cells, like a layer of fine sand evenly covering it. It is different from lactobacilli adsorbed on the surface of vaginal exfoliated squamous epithelial cells. The difference mainly lies in the clarity of the cell edge. Clue cells often appear spotted, jagged, granular, and the edges are blurred. The application of CTB staining technology makes up for the shortcomings of traditional methods. The detection of multiple pathogens is a simpler and faster screening test method, which provides a fast and accurate diagnosis basis for clinical obstetricians and gynecologists to prescribe the right medicine.