Wet mount microscopy reflects functional vaginal lactobacillary flora better than Gram stain

Aim-The status of vaginal lactobacillary flora, an indicator of possible ge nital infection and pregnancy complications, can be assessed on wet mount o r Gram stained specimens. The former is quick, the latter more routine. The accuracy of the two preparative techniques to detect normal vaginal lactob acillary microflora was compared for 646 patients. The effect of delay in t ransport medium before Gram staining was also investigated. Methods-Patients presented with infectious vaginitis or for a routine prena tal visit. After placement of a speculum, duplicate smears were taken from the upper vaginal vault and examined fresh or after Gram staining. Lactobac illary grades from both methods were compared with lactate concentration in vaginal rinses. In a subgroup of 238 patients, Gram staining was performed both on fresh smears and those that had been transported in Stuart's growt h medium. Results-Higher lactobacillary grades (more disrupted flora) were diagnosed 2.9 times more frequently on Gram stained specimens than on wet mounts (p < 0.0001), a difference even more pronounced after transport in Stuart's med ium (relative risk, 4.2; p < 0.0001). Lactobacillary grades assessed on wet mounts correlated better with vaginal lactate concentration than those ass essed on Gram stains. Conclusions-Easier recognition of lactobacillary morphotypes on wet mounts than on Gram stains might result from the loss of lactobacilli by the proce ss of fixation or Gram staining. Wet mount microscopy of vaginal smears for assessment of lactobacillary grades, rather than Gram staining, is strongl y recommended.