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Оглавление9 Bacterial Vaginosis
Gulshan Sethi
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Bacterial vaginosis (BV) is the commonest cause of abnormal vaginal discharge in women of childbearing age, with a prevalence varying from 5% to 50%. It was found in 12% of pregnant women attending an antenatal clinic in the United Kingdom [1], and in 30% in women undergoing termination of pregnancy [2].
Pathophysiology
The pH of the normal vagina is preserved below 4.5. BV generally occurs as a consequence of a disturbance in the vaginal flora resulting in an increase in the pH to 6.0. This is associated with overgrowth of Gardnerella vaginalis and the other anaerobic species (up to a thousandfold), together with a reduction in lactobacilli.
Clinical features
The characteristic symptom of this condition is an offensive vaginal discharge, due to the production of amines such as putrescine, cadaverine, and trimethylamine that give off a characteristic fishy odour [3]. Vaginal inflammation is uncommon; hence, the term vaginosis is used rather than vaginitis. Symptoms may be exacerbated by factors which lead to an increase in vaginal pH such as douching, menstruation, and the presence of semen in the vagina. Although BV occurs more commonly in sexually active women, evidence for its sexual transmission is lacking, and treatment of the sexual partners of women with this condition does not prevent it from recurring [4,5]
Diagnosis
The diagnosis may be made by the fulfilment of Amsel’s criteria [6] or using the Hay–Ison [7] 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.
5 5 Colli, E., Landoni, M. and Parazzini, F. Treatment of male partners and recurrence of bacterial vaginosis: A randomised trial. Genitourin Med. 1997; 73: 267–270.
6 6 Amsel, R., Totten, P.A., Spiegel, C.A. et al. Nonspecific vaginitis: Diagnostic criteria and microbial and epidemiologic associations. Am J Med. 1983; 74: 14–22.
7 7 Ison, C.A. and Hay, P.E. Validation of a simplified grading of Gram stained vaginal smears for use in genitourinary medicine clinics. Sex Trans Inf. 2002; 7: 413–415.
8 8 Nugent, R.P., Krohn, M.A. and Hillier, S.L. Reliability of diagnosing bacterial vaginosis is improved by a standardized method of gram stain interpretation. J Clin Microbiol. 1991; 29: 297–301.
9 9 Ness, R.B., Hillier, S.L., Kip, L.E. et al. Bacterial vaginosis and risk of pelvic inflammatory disease. Obstet Gynecol Surv 2005; 60: 99–100.
10 10 Larsson, P.G., Platz‐Christensen, J.J., Thejls, H. et al. Incidence of pelvic inflammatory disease after first‐trimester legal abortion in women with bacterial vaginosis after treatment with metronidazole: a double blind, randomized study. Am J Obstet Gynecol 1992; 166: 100–103.
11 11 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: 295–298.
12 12 Hillier, S.L. The vaginal microbial ecosystem and resistance to HIV. AIDS Res. Hum. Retrovir. 1998; 14(Suppl. 1): S17–S21.
13 13 Hay, P. National guideline for the management of bacterial vaginosis (2012). Available from: https://www.bashhguidelines.org/media/1041/bv‐2012.pdf. Last accessed September 2021.
