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Gardnerellae
Last reviewed: 06.07.2025
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Morphology of gardnerella
Gardnerella are bacteria, small rods or coccobacilli measuring 1-2x0.3-0.6 µm. In smears, cells are located singly or in pairs. Young 8-12-hour cultures are stained gram-negative, and cultures grown on an optimal medium are gram-positive. They do not have capsules, flagella or spores.
Cultural properties of gardnerella
Facultative anaerobes, capnophiles. Demanding to nutrient media, do not grow on simple nutrient media or show weak growth on blood agar. Grow on special complex nutrient media with the addition of hemin and at 35-37 °C.
Biochemical activity of gardnerella
Fermentation-type metabolism. They break down glucose and maltose into acid. The main fermentation product is acetic acid, some strains are capable of forming succinic and formic acids. Enzymatic activity is low: they do not form catalase and oxidase, they decompose hippurate, and hydrolyze starch.
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Antigenic structure of gardnerella
There are 7 serogroups of gardnerella. The common antigen, which is a glycopeptide, is determined in the expanded RA and ELISA. In RIF, common antigens with Candida albicans were detected.
Pathogenicity factors of gardnerella
Some strains of gardnerella produce neuramidiasis, which destroys glycoproteins of the vaginal mucosa.
Stability In the environment is low. Gardnerella are sensitive to metronidazole and trimethoprim, commonly used antiseptics and disinfectants.
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Pathogenesis of gardnerellosis
The ecological niche is the vagina. Gardnerella together with bacteroides, mobiluncas and other anaerobes cause bacterial vaginosis in women, characterized by disturbances of the vaginal microbiocenosis. Predisposing factors are diabetes mellitus, pregnancy, use of hormonal contraceptives, menopause, endocrine disorders leading to an imbalance of estrogen and progesterone in the body. All this causes a change in the concentration of sugar on the vaginal mucosa and, as a consequence, a decrease in the number of lactobacilli that maintain colonization resistance of the vagina, as a result of which the pH in the vagina becomes higher than 4.5, and gardnerella in association with anaerobes, such as bacteroides, peptostreptococci and mobiluncas, multiply, causing the development of bacterial vaginosis. None of these microbes alone causes vaginosis.
Symptoms of gardnerellosis
Symptoms of gardnerellosis are characterized by the formation of foamy vaginal discharge of white or gray color with a sharp unpleasant fishy odor caused by the formation of abnormal amines. Signs of inflammation are absent. In men, nonspecific urethritis or inflammatory processes of the penis usually develop. Bacterial vaginosis can lead to serious consequences, such as premature birth, decreased body weight of newborns, premature rupture of membranes, inflammatory diseases of the pelvic organs, pathological uterine bleeding. Up to 1/3 of women who present various complaints of discomfort in the vagina suffer from bacterial vaginosis. When an inflammatory component is added and neutrophils appear in the vaginal discharge, vaginosovaginitis develops.
Immunity is not formed after an illness.
Laboratory diagnostics of gardnerellosis
The material for the study is smears from the vagina and cervix. Bacterioscopy and bacteriological methods are used for diagnosis. Usually, the diagnosis is made bacterioscopically by detecting key cells, i.e. vaginal epithelial cells covered with a large number of gram-negative and gram-positive bacteria.
Key cells are covered with a large number of fine rods or coccobacilli, giving the cell surface a granular appearance and unclear outlines. Lactobacilli in Gram-stained smears are almost or completely mixed with a profusely growing bacterial flora consisting of anaerobic bacteria.
In addition, the following clinical signs are used: vaginal discharge has a pH above 4.5; an increase in the amount of sharply watery homogeneous vaginal discharge, the absence of leukocytosis in vaginal discharge; the appearance of a strong odor when a 10% KOH solution is added to the discharge.
Bacteriological examination is rarely performed.