Laboratory diagnosis of Bacterial vaginosis caused by Gardnerella vaginalis

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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.

B. Culture

  • 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

About Author

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Sagar Aryal

Sagar Aryal is a microbiologist and a scientific blogger. He is doing his Ph.D. at the Central Department of Microbiology, Tribhuvan University, Kathmandu, Nepal. He was awarded the DAAD Research Grant to conduct part of his Ph.D. research work for two years (2019-2021) at Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS), Saarbrucken, Germany. Sagar is interested in research on actinobacteria, myxobacteria, and natural products. He is the Research Head of the Department of Natural Products, Kathmandu Research Institute for Biological Sciences (KRIBS), Lalitpur, Nepal. Sagar has more than ten years of experience in blogging, content writing, and SEO. Sagar was awarded the SfAM Communications Award 2015: Professional Communicator Category from the Society for Applied Microbiology (Now: Applied Microbiology International), Cambridge, United Kingdom (UK). Sagar is also the ASM Young Ambassador to Nepal for the American Society for Microbiology since 2023 onwards.

1 thought on “Laboratory diagnosis of Bacterial vaginosis caused by Gardnerella vaginalis”

  1. I am conducting research on microbial isolates and antibiotic sensitivity pattern among women with preterm prelabour rupture of membranes in a Nigerian Teaching Hospital. kindly send me articles on laboratory diagnosis of bacterial vaginosis.


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