Gardnerella vaginalis is the predominant organism in bacterial vaginosis

Department of microbiology and virology

Kharkiv National Medical University

KuzmenkoA.N.

Gardnerella vaginalis is the predominant organism isolated from the vaginal fluid of women with bacterial vaginosis (BV) (1). For more than 25 years, however, this organism's bassociation with the condition has remained poorly understood. In 1955, Gardner and Dukes performed a study in which they isolated G. vaginalis from 138 (92%) of 141 women with BV and from 14 (6%) of 232 women without BV and cited the organism as the causative agent of the syndrome, which they named Haemophilus vaginalis vaginitis (2). However, since that time, published studies have demonstrated that G. vaginalis is often isolated from the vaginal fluid of women who are asymptomatic and lack clinical signs of vaginitis. Bacterial vaginosis (BV) is the most prevalent vaginal infection in women of reproductive age, with a point prevalence of 8%–23% (3). Complications associated with BV include preterm delivery, an increased risk of pelvic inflammatory disease, and an increased susceptibility to HIV acquisition and transmission (4-7). Current treatment, which usually involves metronidazole drug therapy, has not proved sufficient. Even after apparently successful treatment, there is still over a 50% recurrence rate (8-9).

G. vaginalis among women with clinical signs of vaginosis (increased vaginal discharge of fi shy odor, test result “clue cells”, positive amino odor test, pH above) and those without signs of vaginosis. By using a modifi ed biotype scheme it was proven that certain biotypes such as and of G. vaginalis were more frequently accompanied by clinical signs of bacterial vaginosis (10).

Frequent recurrence of bacterial vaginosis, which appear in 20-30% of women during a three-month treatment, is explained with reinfection caused by other biotype of G. vaginalis, different from the source biotype, or as a consequence of wrong treatment (11).

Among microbiological laboratory methods for the diagnosis of bacterial vaginosis is the method of cultivation of G. vaginalis on human two-layer Tween blood agar Minimal diagnostic criteria for identifying G. vaginalis are: appearance of β hemolysis on two-layer Tween blood agar, typical morphology of the colonies, and typical morphology of microorganism using Gram-color staining set, negative catalase test and positive test for hippurate hydrolysis.

Additional differential-diagnostic characteristics of G. vaginalis are negative mannitol fermentation as well as the appearance of inhibition zones on nutritive agar with 50 micrograms of metronidazole and 5 micrograms of trimethoprim. Enzymatic tests (ELISA), molecular-biological (DNA-DNA-hybridization), direct or indirect immunofluorescence (DIF and HF) with polyclonal antibodies are applied for specific detection of G. vaginalis.

Our study goals were to: Determine frequency of Gardnerella vaginalis isolates from vaginal swab among: -women with clinical signs of bacterial vaginosis, -women without clinical signs of bacterial vaginosis; Perform biotypization of isolated types of G. vaginalis; Study relation between infection caused by certain biotypes of G. vaginalis and clinical symptoms and signs of bacterial vaginosis.

Material and Methods

The research was conducted at the Department for Microbiology and virology Kharkiv National Medical University, as well as at the Clinic "Ekomed" at the Ukrain.

A total of 150 women 18-55 years of age were included in the prospective study. Based on clinical examination and presence of one or more signs of internationally accepted Amsel criteria, the examinees were divided into the test and the control group.

Test group consisted of 55 subjects with one or several Amsel signs of bacterial vaginosis. Control group consisted of 47 subjects without Amsel signs of bacterial vaginosis. Each subject, besides registering personal and anamnestic data relevant for diagnosing bacterial vaginosis, was subjected to clinical and microbiological examination. Three swabs of vaginal discharge were taken for microbiological examination, and they were subjected to series of tests.

A direct microscopic preparation was made from the material taken by one swab, using Gram staining method. Using the system for counting characteristic

microorganisms of Gardnerella, Prevotella, Mobiluncus and Lactobacilus morphotypes, the condition of vaginal flora was assessed following Nugent method.

he second swab sample was cultivated in commercial selective medium for G. vaginalis produced. After the cultivation for 48 hours at 37C, in atmosphere enriched with CO₂, the identification of grown colonies was conducted by application of standard microbiological methods. Isolated types of G. vaginalis were identified based on reaction to the following tests: catalase, oxidase, hippurate hydrolysis, activity of lipase and ß galactosidase, arabinose and xylose.

Results

Test results of clinical signs of bacterial vaginosis according to Amsel. After clinical examination, 46% of the subjects were found with one or more clinical signs of bacterial vaginosis according to Amsel.

In comparison to the control group, G. vaginalis, Trichomonas vaginalis and Veilonella species were significantly more abundant in the test group.

The following biotypes were found among the isolated types of G. vaginalis: biotype 1 (2 isolate), biotype 2 (9 isolates), biotype 3 (14 isolates), biotype 4(4 isolates), biotype 5 (12 isolates), biotype 7 (2 isolates). The most common biotypes were: 3, 5 and 2. Among the total of 150 tested samples of vaginal swabs, Candida albicans was isolated in 35 samples (17,5%), and Trichomonas vaginalis was found in 5 samples (2,7%).

After the analysis of biochemical characteristics of all G. vaginalis isolates, biotypization was completed for all types 27/30 (95%) following Piot method, while Benit method produced the results in 20 of 30 (65.5%). Signifi cant diff erence was registered in abundance of biotypes 2, 3 and 5. between the test and control group (p<0,05).

The biotypization analysis results showed that biotype 3 and 5. G. vaginalis was significantly more present in comparison to the other causative agents that are associated with the clinical signs of bacterial vaginosis.

The isolation of G. vaginalis directly depends on the number of noticeable clinical signs of bacterial vaginosis. he highest percentage of G. vaginalis isolates was found among persons who exhibited all four clinical signs. G. vaginalis was not isolated from samples of vaginal discharge of subjects who exhibited only one clinical sign.

Bacterial vaginosis is diagnosed in 35% women with subjective discomfort characteristic of vaginal infection, and in 52% women with subjective discomfort characteristic of bacterial vaginosis.

G. vaginalis was isolated from vaginal discharge of women without clinical signs characteristic of bacterial vaginosis.

Isolation of G. vaginalis was signifi cantly more frequent (p<0,05) in the group of women with clinical signs of bacterial vaginosis in comparison to the group of women without these signs.

Piot biotypization scheme showed that biotypes 2, 3 and 5. of G. vaginalis were signifi cantly more frequently isolated in women diagnosed with bacterial vaginosis. In the group of women without clinical signs of bacterial vaginosis, biotype 5.

Lipase positive types of G. vaginalis were signifi cantly more frequently associated with the syndrome of bacterial vaginosis.

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