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Laboratory diagnosis of Bacterial vaginosis caused by Gardnerella vaginalis
Specimen: Vaginal discharge specimen
A. Direct Microscopic Examination
- Bacterial Vaginosis (BV) is characterized by a foul-smelling discharge.
- A diagnosis/confirmation is done microscopically by examination of gram stains to detect change in vaginal ecology.
- A smear of vaginal fluid or vaginal swab is gram stained which reveals the presence of Gram negative bacilli sometimes Gram variable.
- It requires enriched media such as blood agar, loeffler’s serum slope or dextrose starch agar.
- Optimum temperature is 37°C and optimum pH is 6.8 for growth, incubation for 48 hours.
- Growth is enhanced by 5% carbondioxide and moisture .
- Colony morphology : small domed colonies surrounded by beta hemolysis develop in human or rabbit blood agar
- There is a zone of clearing on dextrose starch agar.
C. Amsel criteria
Besides the Gram stain, BV can be diagnosed by using the Amsel criteria (Clinical Diagnosis):
- Thin, white, yellow, homogeneous discharge.
- pH measurement of vaginal fluid >4.5
- Performance of an amine test: Release of a fishy odor on adding alkali—10% potassium hydroxide (KOH) solution (Whiff Test)
- Wet mount microscopy of vaginal secretions: observation for clue cells
Treatment of Bacterial vaginosis
- Oral metronidazole is generally curative.
- Besides these clindamycin can be suggested as topical use.
Prevention and control of Bacterial vaginosis
- Personnel hygiene
- Avoidance of multiple sex partner