9Bacterial Vaginosis
Gulshan Sethi
Bacterial vaginosis (BV) is the commonest cause of abnormal vaginal discharge in women of childbearing age, with a prevalence varying from 5% to 50%. It was found in 12% of pregnant women attending an antenatal clinic in the United Kingdom [1], and in 30% in women undergoing termination of pregnancy [2].
Pathophysiology
The pH of the normal vagina is preserved below 4.5. BV generally occurs as a consequence of a disturbance in the vaginal flora resulting in an increase in the pH to 6.0. This is associated with overgrowth of Gardnerella vaginalis and the other anaerobic species (up to a thousandfold), together with a reduction in lactobacilli.
Clinical features
The characteristic symptom of this condition is an offensive vaginal discharge, due to the production of amines such as putrescine, cadaverine, and trimethylamine that give off a characteristic fishy odour [3]. Vaginal inflammation is uncommon; hence, the term vaginosis is used rather than vaginitis. Symptoms may be exacerbated by factors which lead to an increase in vaginal pH such as douching, menstruation, and the presence of semen in the vagina. Although BV occurs more commonly in sexually active women, evidence for its sexual transmission is lacking, and treatment of the sexual partners of women with this condition does not prevent it from recurring [4,5]
Diagnosis
The diagnosis may be made by the fulfilment of Amsel’s criteria [6] or using the Hay–Ison [7] or Nugent [8] methods to examine the vaginal discharge.
Amsel’s criteria
To fulfil Amsel’s criteria, at least three of the following must be present:
- Thin, white, homogeneous discharge.
- Clue cells (vaginal epithelial cells covered with multiple gram‐variable organisms so that their edges are completely obliterated) on microscopy of wet mount (Figure 9.1).
- pH of vaginal fluid > 4.5.
- Release of a fishy odour with 10% potassium hydroxide.
Microscopic examination to look for clue cells is not necessary for a diagnosis to be made using Amsel’s criteria as long as the other three factors can be demonstrated.
Hay–Ison method
The Hay–Ison method of diagnosis uses microscopy and classes the results as the following.
- Grade 1 (normal): Lactobacilli predominate.
Figure 9.1 Clue cell.
Source: Published in Wisdom, A and Hawkins, Diagnosis in Color: Sexually Transmitted Diseases, 2nd edn. Mosby‐Wolfe, London slide 283, p. 163, © Elsevier 1997.
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