Anaerobic Vaginosis

Bacterial Anaerobic Vaginosis (Gardnerella)

The above terms refer to a condition that occurs when the normal vaginal bacteria (lactobacilli) are displaced by anaerobic bacteria – mainly by a bacterium called Gardnerella vaginalis. The cause is unknown and, in fact , Gardnerella vaginalis can often be found on routine testing of women who do not have any symptoms or signs of the condition. The normal pH (a measure of the acidity in the vagina) is usually around 3 but in anaerobic vaginosis this pH rises to 5 or 6. This is the opposite to the situation that occurs in Thrush when the pH goes down to 2.

Although it is more common in women who are sexually active, it is NOT considered a sexually transmitted condition and no real benefit has ever been shown by treating the male partner.


Typically there is a thin greyish discharge that occasionally has a fishy smell, particularly after intercourse. It can be difficult to distinguish clinically from Thrush, but there is usually less itching and irritation with anaerobic vaginosis than with Thrush. It never causes an ascending infection (ie. An infection that ascends up through the uterus and out to the fallopian tubes) so it is not a cause of pelvic inflammatory disease and, even in recurrent cases, no long term damage is done.


The discharge can be examined under a microscope and, if due to anaerobic vaginosis, “clue cells” (vaginal epithelial cells covered with Gardnerella vaginalis bacteria) are seen.


Treatment is simple. An antibiotic called Metronidazole tablets (Flagyl) is given either as a single large dose (2 gram) or, alternatively, as a twice a day dosage for one week. The tablets have to be taken with food. Patients must not drink alcohol whilst on the course of tablets. Recurrences may be helped by using a gel that lowers the vaginal pH ( Acigel).

Clindamycin (Dalacin C) vaginal cream and Metronidazole gel (Zidoval) are alternative treatments, applied directly to the vagina. They are as effective as Metronidazole tablets, and avoid the need for taking tablets.