Bacterial vaginosis refers to an overgrowth of predominantly anaerobic microorganisms in the vaginal flora.
Bacterial vaginosis (BV) refers to a condition where there is disruption in the normal vaginal flora. There is an excess of anaerobic microorganisms and loss of the normal lactobacilli, which leads to a vaginal odour and increased discharge.
The condition is a not a sexually transmitted infection (STI) but it occurs more commonly in sexually-active women.
BV is the most common cause of vaginal discharge in women of childbearing age.
Almost one third of women between the ages of 14-49 years old have evidence of BV. It is highest amongst women who are sexually active.
BV is seen more commonly in black women. Women who have sex with women are more at risk due to shared vaginal flora patterns.
BV occurs due to a loss of the usual lactobacilli bacteria within the vaginal flora.
The exact trigger for BV is unknown. However, a rise in the vaginal flora pH >4.5 creates an alkaline environment that favours colonisation by anaerobic organisms, such as Garnerella vaginalis and loss of the usually dominant lactobacilli.
Example of organisms found in BV:
It is the alteration in the relationship between G. vaginalis, other organisms and Lactobacilli that leads to the development of BV. This is often described as a synergistic polymicrobic infection.
The absence of inflammation BV is why the term vaginosis is preferred to ‘vaginitis’, which implies inflammation.
The presence of a vaginal odour is the most common presenting symptom.
The diagnosis of BV is based on the Amsel criteria.
The diagnosis of BV can be made when three of the four Amsel criteria are met:
Other conditions such as trichomoniasis and candidiasis may present similarly to BV. These conditions are usually associated with soreness, itching or irritation. Remember there could be co-infection and samples are usually required to differentiate between these pathologies.
Investigations are needed for a formal diagnosis of BV.
Formal examination of the vulva with speculum examination is needed to make a diagnosis of BV. However, patients who fulfil certain criteria with features that are highly specific for BV may be treated empirically.
Samples should be taken from the lateral wall and then tested for pH using a low-range pH paper. Normal vaginal pH in women of child-bearing age is 3.5-4.5. Samples with pH > 4.5 is suggestive of BV.
Samples can also be checked for Clue cells by using microscopy. Clue cells refer to vaginal epithelial cells that have many coccobacilli adherent to their surface, giving a studded appearance and less sharply defined border.
Consider testing for the following STIs and referring as necessary to a genito-urinary medicine (GUM) clinic among high-risk patients.
Oral metronidazole is the treatment of choice in symptomatic patients.
Patients may be given empirical treatment based on the history if there is a low risk of STI and none of the following factors are present:
Recurrent episodes may be treated empirically if they have been previously confirmed following examination.
Women who are asymptomatic do not require treatment unless they are undergoing termination of pregnancy. The treatment of women who are symptomatic depends on pregnancy status.
NOTE: Clindamycin can be used as an alternative as both an oral or intravaginal preparation.
In patients with persistent symptoms despite treatment it is important to check adherence to previous treatment. A speculum examination should be performed with high vaginal swabs if previously empirically treated.
Consider giving a full course of seven days of metronidazole if previously treated with the single dose course. If there is no response the consider referral to a GUM or gynaecological clinic for further investigation. If associated with an intrauterine contraceptive device (IUD), consider removal.
Recurrence of symptoms of BV is common in women and usually requires a further course of treatment. Important to check adherence to previous treatment. If a speculum examination has not previously be done this should be completed with high vaginal swabs.
The new episode should be treated with a seven day course of metronidazole. Prophylactic intravaginal treatment can be considered if ≥4 episodes in one year, but this is off-label. Consider GUM/Gynaecology clinic referral.
BV is associated with an increased risk of post-surgical infections (e.g. post-C-Section).
BV increases the risk of salpingitis, endometrititis and infections following gynaeolcogical surgery (e.g. post-hysterectomy, post-cesarean). Also increases risk of complications in pregnancy (e.g. premature rupture of membranes, preterm labour).
For more information see NICE CKS guidelines.
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