A comparison of acridine orange, wet microscopy and gram staining in the diagnosis of bacterial vaginosis

Abstract

Bacterial vaginosis (BV) is a common condition affecting women in genito-urinary medicine. Although the majority of patients are asymptomatic, some may present with offensive, vaginal discharge and occasional vulvovaginal irritation. 1 Lactobacilli are the predominant bacteria in the normal vagina and control the vaginal flora at low pH. Bacterial vaginosis is a polymicrobial condition in which there is a fall in the vaginal acidity and in the concentration of commensal lactobacilli. 2 This fall is then accompanied by an increase of more than a lO0-fold in the concentration of other micro-organisms. These include anaerobes such as Gardnerella and Mobiluncus sp. The mechanism for this change remains unknown, but may be related to antibiotic usage, sexual activity and menstrual cycle changes. It is the commonest cause of vaginal discharge affecting up to 25% of women. 3 The optimal method of diagnosing bacterial vaginosis remains controversial. In Amsel's clinical description, the diagnosis of BV is made on the presence of at least three of the following four clinical criteria: (1) positive amine test, (2) pH of the vaginal secretions >4.5, (3) homogeneous vaginal discharge or (4) presence of clue cells on the wet mount preparation (WM). * The presence of clue cells has previously been shown to be extremely specific and sensitive for diagnosing BV when combined with these clinical criteria. 5 Other more exact methods of diagnosing BV have been assessed including the Gram stain interpretative methods focusing on the quantification of bacterial morphotypes. ('' 7 These methods give comparable results with Amsel's criteria; however, they require enumerat ion of bacterial morphotypes making interpretation less standardized and more time consuming. Acridine orange (AO) is a fluochrome dye which differentially stains the nucleic acids of micro-organisms.