Microbiology

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Appropriate specimens are often difficult to obtain and incorrect or sub-optimal specimens are often received.  It is important to avoid contamination with vulva faecal flora during collection of specimens. After the introduction of the speculum, roll the swab firmly over the surface of the vaginal vault.  Then place the swab in transport medium with MW176 Liquid swab.

A range of sexually transmissible organisms cause infections responsible for a large number of clinical syndromes.  When a specific STI is diagnosed, it is recommended to screen for other infections.  Screening has a role in helping to control gonorrhoea, syphilis, chlamydial infection, and human immunodeficiency virus (HIV) infection

Bacterial Vaginosis (BV) is now considered to be associated with a variety of genital tract infections and complications. BV may be diagnosed clinically if three of the following four criteria are fulfilled:
• Grey-white, thin homogenous discharge
• Vaginal secretions pH > 4.5
• Positive amine odour test (release of fishy amine odour when vaginal secretion is mixed with 5-10% potassium hydroxide)
• Presence of clue cells on microscopic examination

Gram staining of vaginal smears using Hay’s criteria is the most sensitive method for the laboratory diagnosis of BV as it detects both clue cells and the disturbance in bacterial morphotypes associated with BV.

 Gram stains performed only when indicated by clinical details

Investigation for Trichomonas vaginalis is no longer routinely performed on HVS samples. Please contact the laboratory if clinically indicated.

Send sample to the laboratory without delay.  Sample should be refrigerated if not transported immediately

Related links

VAGINAL DISCHARGE REFERENCE GUIDE

Reference range

Hay’s criteria of Gram Stained Vaginal Smears
Grade I:  normal  predominantly Lactobacillus morphotypes
Grade II: intermediate  mixed Lactobacillus and other morphotypes. Assess with clinical criteria and send repeat to confirm if necessary
Grade III:  abnormal  few or absent Lactobacillus morphotypes, but greatly      increased number of G. vaginalis and other bacterial      morphotypes. Suggestive of BV

Hays criteria can not be applied in prepubertal (<12 years) or postmenopausal females (>65years) and the presence or absence of WBCs and yeasts is reported.

A negative microscopy result does not exclude the possibility of TV infection
The absence of N. gonorrhoeae in vaginal swabs is not reported as this is not the specimen of choice for the isolation of N. gonorrhoeae.

Strep. agalactiae (BHS Group B) susceptibilities are reported from HVS samples where clinical details of pregnancy are indicated.  Strep pyogenes (BHS Group A) susceptibilities are reported in all cases.

Last updated

Thu, 21 Dec 2023 12:10:37 GMT