Vaginal Gram Stain

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The image on the left is a smear from a normal vagina displaying large numbers of long slender Gram positive bacilli tending to be arranged in chains. This is the typical morphology of Lactobacillus spp.

The image on the right is from a woman with Bacterial Vaginosis. There are no Lactobacillus spp. There are large numbers of small Gram variable bacilli (Gardnerella “morphotype”), large numbers of small, curved Gram negative bacilli (Mobiluncus “morphotypes”) and large numbers of Gram-negative cocco-bacilli (Bacteroides “morphotypes”). The large cell is a vaginal squamous epithelial cell with masses of bacteria adherent to it. This is referred to as a clue cell and is very suggestive of bacterial vaginosis.