Assessment of vaginal lactobacillary flora in wet mount and fresh or delayed gram's stain

The assessment of the vaginal lactobacillary flora helps to direct further diagnostic microbiologic investigations in genital infectious disease and seems to represent a powerful tool in predicting infectious morbidity and preterm labor during pregnancy. In the absence of a "gold standard," we studied the variations in assessing lactobacillary morphotypes according to the method used.

The lactobacillary flora from 183 pregnant women was classified according to 3 groups: normal, intermediate, and abnormal. This grading of lactobacilli was appled to vaginal and cervical specimens by means of 1) immediate wet-smear microscopy, 2) Gram's stain on a fresh, air-dried specimen, and 3)delayed Gram's stain after specimen transportation in Stuart's growth medium for 3-6 h.

The assignment of intermediate or abnormal flora (grade II or grade III) showed high concordance rates among the different preparatory techniques, but the assignment of grade I (normal flora) did not. Fewer lactobacilli were found 2.6 times more often after Gram's stains of fresh specimens [Relative Risk (RR) 2.6, 95% confidence interval (CI) 1.7-4.1] and 6 times more often when the Gram%s stain was performed in a delayed examination after transport than in a fresh wet-mount specimen (RR 6.2, 95% CI 2.5-15.6). Disturbed lactobacillary grades were also found more frequently in specimens from the cervix than those from the vagina (RR 4.0, 95% CI, 1.5-10.4).

There are discrepancies in the diagnosis of lactobacillary grades between gram-stained and fresh vaginal specimens. The evidence is ambiguous as to which of the 2 methods is responsible. If an evaluation is to be done on a gram-stained specimen, then the storage of the sample in Stuart transport medium before staining should be avoided.