What are Nugent’s criteria for grading bacteria in suspected bacterial vaginosis (BV)?

Updated: Oct 25, 2018
  • Author: Philippe H Girerd, MD; Chief Editor: Michel E Rivlin, MD  more...
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The bacterial flora may be examined microscopically for evidence of changes in the overall bacterial predominance. The healthy vagina has a predominance of lactobacilli (large gram-positive rods). The flora of a patient with BV changes to become dominated by coccobacilli, reflecting an increase in the growth of Gardnerella vaginalis and other anaerobes.

Many use Nugent's criteria to quantify or grade bacteria via Gram stain of vaginal samples. In brief, Nugent's criteria evaluate 3 types of bacteria via Gram stain: Lactobacillus, Bacteroides/Gardnerella, and Mobiluncus. They are each graded on a scale of 1-4 (1+ is < 1 cell per field, 2+ is 1-5 cells per field, 3+ is 6-30 cells per field, and 4+ is >30 cells per field). In this system, Lactobacillus and Bacteroides/Gardnerella are given scores between 0-4 but Mobiluncus is only graded from 0-2. Total scores are then calculated and used as follows: 0-3 (Normal), 4-6 (intermediate bacterial count), and 7-10 (bacterial vaginosis). [15]

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