Clue Cells in Bacterial Vaginosis: Immunofluorescent Identification of the Adherent Gram-Negative Bacteria as Gardnerella vaginalis

Clue cells are epithelial cells covered by adherent gram-negative rods, observed in vaginal smears from women with bacterial vaginosis. Immunofluorescence studies were used to identify the gram-negative bacteria adhering to clue cells. Specific antisera to four com-mon gram-negative vaginal bacteria (Gardnere//a, Bacteroides, Fusobacterium, and Mobiluncus) were prepared by long-term, multiple, small-inoculum immunization of rab-bits. Cross-reactivity with heterologous common vaginal bacteria was removed byabsorp-tion against whole cellsof heterologous bacteria and by serial dilution. Gardnerella vaginalis was most often observed adhering to the surface of clue cells and was detected on the surface of exfoliated vaginal epithelial cells significantly more frequently and in higher numbers than wereMobiluncus, Bacteroides, and Fusobacterium, suggesting that this spe-cies of gram-negative bacteria is responsible for clue cell formation. Epithelial cells covered with adherent gram-negative bacilli are frequently observed in vaginal smears from women with bacterial vaginosis but not in clinically normal women. Gardner and Dukes [1] named thes