Objective: To relate Gram-stained smears, using the Nugent criteria, to quantitative and qualitative vaginal cultures in pregnant women.
Methods: Two independent evaluators using the Nugent criteria, a standardized method of Gram-stain interpretation designed to detect bacterial vaginosis, scored 104 vaginal smears from pregnant women. The quantitative and qualitative vaginal cultures were assessed at the same time and the results expressed as log(10) colony-forming units per gram of vaginal secretion. The Nugent scores were compared with the microbiologic findings.
Results: The prevalence of normal, intermediate, or bacterial vaginosis vaginal flora as determined by Gram stain was 68%, 21%, and 11%, respectively. A comparison of the mean bacterial counts with the Nugent score showed a weak negative correlation for Lactobacillus species and a positive correlation for gram-variable and gram-negative rods. Additional analysis revealed a strong positive correlation between the mean bacterial counts analyses of Peptostreptococcus, a genus not included in the Nugent scoring system, and the Nugent score. In addition, the Prevotella counts correlated strongly with both the Nugent score and the Peptostreptococcus counts. The quantitative counts for Lactobacillus did not vary significantly among the three defined groups of vaginal microflora; however, significant increases in the concentrations of Gardnerella vaginalis and Prevotella were found as the Nugent score increased.
Conclusion: A strong correlation was found among the gram-variable and gram-negative genera comprised by the Nugent score. Peptostreptococcus also correlated strongly with the Nugent score and with the Prevotella counts, suggesting that this genus may play a role in determining vaginal health.