A vaginal discharge with fishy odor after 10% KOH and a wet mount showing epithelial cells and gram-variable rods most likely indicates infection with which organism?

A vaginal discharge with fishy odor after 10% KOH and a wet mount showing epithelial cells and gram-variable rods most likely indicates infection with which organism?

• A. Gardnerella vaginalis
• B. Candida albicans
• C. Trichomonas vaginalis
• D. Escherichia coli

Answer: (A)

This presentation is classic for bacterial vaginosis caused by Gardnerella vaginalis. The fishy odor that appears after a 10% potassium hydroxide prep, known as the whiff test, arises from volatile amines produced by the abnormal vaginal flora. On a wet mount, the hallmark is clue cells—vaginal epithelial cells covered with bacteria—along with gram-variable rods, which are characteristic of Gardnerella. Understanding the alternatives helps reinforce this pattern: Candida albicans typically causes itching and a thick, cottage-cheese discharge and shows budding yeast or pseudohyphae on KOH prep rather than gram-variable rods with clue cells. Trichomonas vaginalis would reveal motile protozoan trophozoites on the wet mount and usually presents with a frothy, sometimes yellow-green discharge and irritation. Escherichia coli is not associated with the BV-specific pattern of clue cells and the fishy odor after KOH.

This presentation is classic for bacterial vaginosis caused by Gardnerella vaginalis. The fishy odor that appears after a 10% potassium hydroxide prep, known as the whiff test, arises from volatile amines produced by the abnormal vaginal flora. On a wet mount, the hallmark is clue cells—vaginal epithelial cells covered with bacteria—along with gram-variable rods, which are characteristic of Gardnerella.

Understanding the alternatives helps reinforce this pattern: Candida albicans typically causes itching and a thick, cottage-cheese discharge and shows budding yeast or pseudohyphae on KOH prep rather than gram-variable rods with clue cells. Trichomonas vaginalis would reveal motile protozoan trophozoites on the wet mount and usually presents with a frothy, sometimes yellow-green discharge and irritation. Escherichia coli is not associated with the BV-specific pattern of clue cells and the fishy odor after KOH.