Introduction
Bacterial Vaginosis, previously known as nonspecific vaginitis or Gardnerella vaginitis, is the most common cause of vaginal discharge. It may be the cause of up to one half of cases of vaginitis in all women and the cause of from 10 to 30 percent of cases in pregnant women. This clinical syndrome is now recognized as a polymicrobial superficial vaginal infection involving a loss of the normal lactobacilli and an overgrowth of anaerobes. While commonly found in increased numbers in women with bacterial vaginosis, Gardnerella vaginalis is not invariably present. G. vaginalis has been reported in from 16 to 42 percent of women with no signs or symptoms of vaginitis.
Clinical Features
Symptoms
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Offensive fishy smelling vaginal discharge |
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Not associated with soreness, itching, or irritation |
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Many women (approximately 50%) are asymptomatic |
Signs
Thin, white, homogeneous discharge, coating the walls of the vagina and vestibule.
Complications
Bacterial vaginosis is associated with an increased risk of several pathologic conditions, including postoperative infection following hysterectomy and postabortion pelvic inflammatory disease. The risk of plasma cell endometritis in women with bacterial vaginosis has been reported to be 15 times higher than the risk in women without bacterial vaginosis (95 percent confidence interval; range: 2 to 686).
In pregnant women, bacterial vaginosis is associated with the presence of fetal fibronectin. Women with fetal fibronectin have a 16-fold increase in clinical chorioamnionitis and a sixfold increase in neonatal sepsis. The microorganisms found in bacterial vaginosis are also commonly found in the amniotic fluid of women with amniotic fluid infection. Women with bacterial vaginosis have an odds ratio of 1.85 (confidence interval: 1.16 to 2.9) for intra-amniotic infection. Bacterial vaginosis in women at 23 to 26 weeks of gestation is associated with intra-amniotic fluid infection at term.
Diagnosis
In clinical practice BV is diagnosed using the Amsel criteria. At least three of the four criteria are present for the diagnosis to be confirmed.
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Thin, white, homogeneous discharge |
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Clue cells on microscopy |
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pH of vaginal fluid >4.5 |
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Release of a fishy odour on adding alkali (10% KOH) |
Alternatively Gram stained vaginal smear, with the Nugent Criteria
The Gram-stained smear is a cheap, fast and easy method. It provides good results for diagnosis of bacterial vaginosis.
The Nugent score is derived from estimating the relative proportions of bacterial morphotypes to give a score between 0 and 10. A score of <4 is normal, 4-6 is intermediate, and >6 is BV10.
Gram stained smears were scored following a morphotype classification:
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Lactobacillus: Large Gram-positive rods (scored 4 to 0), |
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Gardnerella/ Bacteroides spp.: small Gram variable coccobacilli /small Gram-negative rods (G. vaginalis, scored 0 to 4) |
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Mobiluncus spp.: thin, curved, Gram-variable rods (Mobiluncus morphotypes, scored 0 to 2) |
The scoring system (0 to 10) is a weighted combination of these morphotypes: a+b+c.
Table 1 The Nugent scoring system
Score |
Lactobacillus Morphotype
per field |
Gardnerella morphotype per field |
Curved bacteria (Mobiluncus) per field |
0 |
>30 |
0 |
0 |
1 |
5-30 |
<1 |
1-5 |
2 |
1-4 |
1-4 |
>5 |
3 |
<1 |
5-30 |
----- |
4 |
0 |
>30 |
----- |
The criterion for bacterial vaginosis according to Nugent's criteria is a total score of 7 or more is labeled as Bacterial Vaginosis a score of 4 to 6 is called intermediate, and a score of 0 to 3 is considered normal.
