A vaginal pH was taken and found to be 5.7. What is the SINGLE most likely causative organism?

A 41 year old woman presents with an offensive malodorous vaginal discharge. The discharge is clear in colour and has a distinctive fishy odour. A vaginal pH was taken and found to be 5.7. What is the SINGLE most likely causative organism?

A. Gardnerella vaginalis
B. Trichomonas vaginalis
C. Candida albicans
D. Chlamydia trachomatis
E. Neisseria gonorrhoeae

Bacterial vaginosis and Trichomonas vaginalis can give foul smelling discharge. Bacterial vaginosis which is mostly caused by an overgrowth of Gardnerella vaginalis causes vaginal discharge which is grey-white and has a “fishy” smell. The characteristic “fishy smell” is a clincher and one should pick Bacterial vaginosis (Gardnerella vaginalis) as the answer. In trichomonas vaginalis, it can be a greenish and frothy along with vulvovaginitis i.e. strawberry cervix. The discharge of Chlamydia and Gonorrhea is not usually foul smelling. Candida albicans (vaginal candidiasis) has a white, ‘cheesy’ discharge. The discharge is non-offensive. Bacterial vaginosis Bacterial vaginosis (BV) is caused by an overgrowth of mixed anaerobes,such as Gardnerella vaginalis, which replace the usually dominant vaginal lactobacilli resulting in a raised vaginal pH. It is the commonest cause of abnormal vaginal discharge in women of childbearing age. Whilst BV is not a sexually transmitted infection it is seen almost exclusively in sexually active women. Features • Vaginal discharge: ‘fishy’, offensive The characteristic ‘fishy’ smell is due to the presence of amines released by bacterial proteolysis and is often the reason women attend the clinic • Asymptomatic in 50% Amsel’s criteria for diagnosis of BV → 3 out of 4 required for diagnosis: • Homogenous grey-white discharge • Characteristic fishy smell • ‘Clue cells’ present on microscopy • Vaginal pH > 5.5 Management May resolve spontaneously and if successfully treated has a high recurrence rate. However, most women prefer it to be treated. • Metronidazole 400mg orally bd for 5 days or metronidazole 2g (single dose) OR • Clindamycin 2% cream vaginally at night for 7 days