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, PhD

Dr. Sagar Aryal is a microbiologist, researcher, and science communicator from Nepal. He is also co-founder and Research Head of the Department of Natural Products at the Kathmandu Research Institute for Biological Sciences (KRIBS), where he leads research on natural product discovery and microbial biodiversity. Dr. Aryal earned his Ph.D. in Microbiology from Tribhuvan University, Kathmandu, Nepal, in 2025, supported by a DAAD Research Grant and a University Grants Commission (UGC) Nepal Ph.D. Fellowship. His research interests include Actinomycetes, Myxobacteria, microbial taxonomy, and natural products, particularly the discovery of bioactive compounds with potential pharmaceutical applications. He isolated and identified Nocardia nepalensis, a novel bacterial species from Nepal, contributing to understanding microbial diversity in the region. Dr. Aryal has published more than 16 research articles in international journals and contributed three book chapters to established academic publications. He has presented scientific research findings and developed international research collaborations through visits to more than 18 countries across Asia, Europe, North America, and Oceania. From 2023 to 2025, he served as the American Society for Microbiology (ASM) Young Ambassador to Nepal. Since December 2025, he has served as an Editorial Board Member of Scientific Reports, a Nature Portfolio journal. In recognition of his scientific contributions, Dr. Aryal received the NAST Science and Technology Youth Award 2025 from the Nepal Academy of Science and Technology. He previously received the Frs. Locke and Stiller Research Award (LSRA) for the 2017-2018 cycle from St. Xavier's College, Kathmandu, and a Nepal Academy of Science and Technology (NAST) Research Grant for 2017-2018. Alongside his scientific career, Dr. Aryal has more than 15 years of experience in blogging, content writing, and search engine optimization (SEO).

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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