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:
1 Thin, white, homogeneous discharge.
2 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).
3 pH of vaginal fluid > 4.5.
4 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.
Grade 2 (intermediate): Mixed flora with some Lactobacilli, but Gardnerella or Mobiluncus species also present.
Grade 3 (BV): Predominantly Gardnerella and/or Mobiluncus species. Lactobacilli are few or absent.
Nugent score
This is derived by estimating the relative proportions of different bacteria to produce a score between 0 and 10. A score of <4 is normal; 4–6 is intermediate; and >6 indicates BV.
The Hay–Ison and Nugent methods do not lend themselves easily to application outside of a specialist setting. Culture of vaginal fluid may grow G. vaginalis; however, this does not constitute a definitive diagnosis of BV as this organism can be found as a commensal.
Differential diagnosis
There is a wide differential diagnosis including other infective and non‐infective causes (see Table 9.1).
Complications
Women with BV have an increased risk of many obstetric and gynaecological complications. These include pelvic inflammatory disease [9], post‐termination of pregnancy endometritis [10] and late miscarriage [11], preterm birth or rupture of membranes and postpartum endometritis [11], and an increased risk of infective complications after hysterectomy. In addition, in prospective studies, BV has emerged as a risk factor for acquisition of sexually transmitted infection, including human immunodeficiency virus (HIV) infection [12].
Table 9.1 Differential diagnosis of bacterial vaginosis
| Infective | Non‐infective |
|---|---|
| Candidiasis | Normal physiological discharge |
| Trichomoniasis | Malignancies |
| Chlamydia infection | Atrophic vaginitis |
| Gonorrhoea | Foreign body i.e. tampon |
| Herpes simplex | Allergy i.e. to chemicals or latex |
| Mechanic irritation due to lack of lubrication |
Treatment
Treatment of asymptomatic women is not necessary, although if diagnosed incidentally they may choose to be treated. Patients should be advised to avoid vaginal douching, use of shower gel, and use of antiseptic agents or shampoo in the bath. The following treatment regimens are recommended by the British Association for Sexual Health and HIV (BASHH) [13]:
Metronidazole 400 mg orally twice daily for 5–7 days
Metronidazole 2 g orally as a single dose
Metronidazole gel (0.75%) intravaginally once daily for 5 days
Clindamycin cream (2%) intravaginally once daily for 7 days
Clindamycin 300 mg orally twice daily for 7 days
Tinidazole 2 g orally as a single dose
Prognosis and follow‐up
There is no need to perform a test of cure if symptoms resolve. A clear verbal and written explanation of BV should be provided by the clinician. When giving information to patients, the clinician should inform the patient about the treatment being given, how to take it and its possible adverse effects, that BV can recur following treatment but will respond to standard treatments, and that there is no need to screen and treat sexual partners for BV. Routine sexually transmitted infections (STIs) screening should be offered in accordance with current testing guidelines.
Resources
BASHH guidelines
https://www.bashhguidelines.org/media/1041/bv‐2012.pdf
Patient information leaflet
https://www.bashhguidelines.org/media/1028/bv‐pil‐screen‐edit.pdf
Last accessed September 2021.
References
1 1 Hay, P.E., Lamont, R.F., Taylor‐Robinson, D. et al. Abnormal bacterial colonisation of the genital tract and subsequent preterm delivery and late miscarriage. Br Med J. 1994; 308(6924): 295–298.
2 2 Blackwell, A.L., Thomas, P.D., Wareham, K. and Emery, S.J. Health gains from screening for infection of the lower genital tract in women attending for termination of pregnancy. Lancet. 1993; 342(8865): 206–210.
3 3 Brand, J.M. and Galask, R.P. Trimethylamine: the substance mainly responsible for the fishy odour often associated with bacterial vaginosis. Obstet Gynecol. 1986; 63: 682–685.
4 4 Larsson, P.G. Treatment of bacterial vaginosis. Int J STD AIDS. 1992; 3: 239–247.
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