Bacterial vaginosis

Background

Microbiology

• Shift in vaginal flora from Lactobacillus to high bacterial diversity that includes facultative anaerobes
• The new flora includes: Gardnerella vaginalis, Prevotella species, Porphyromonas species, Bacteroides species, Peptostreptococcus species, Mycoplasma hominis, Ureaplasma urealyticum, Mobiluncus species, Megasphaera species, Clotridiales species, Fusobacterium species, and Atopobium species

Pathophysiology

• The new bacterial flora produce volatile amines, which increases the vaginal pH >4.5 (from the normal range of 4 to 4.5)

Diagnosis

Amsel Criteria

• Requires microscopy but not Gram staining
• At least three of the following criteria:
  • Characteristic vaginal discharge: homogeneous, thin, grayish-white discharge that smoothly coats the vaginal walls
  • Elevated pH >4.5
  • Clue cells on saline wet mount, which are vaginal epithelial cells studded with adherent coccobacilli
  • Positive whiff-amine test, where a fishy odor is detected after a drop of 10% KOH is added to a sample of vaginal discharge

Nugent Criteria

• Based on the Gram stain
• Considered the gold standard, but is more resource-intensive than wet mount microscopy used for Amsel criteria

Score	Lactobacillus	Gardnerella and Bacteroides	Curved gram-variable bacilli
0	4+	0	0
1	3+	1+	1+ or 2+
2	2+	2+	3+ or 4+
3	1+	3+
4	0	4+

• Interpretation is based on total score:
  • 0 to 3: normal
  • 4 to 6: indeterminate
  • 7 to 10: bacterial vaginosis

Others

• Culture is not relevant to diagnosis of bacterial vaginosis

Management

Non-Pregnant Woman

• First-line:
  • Metronidazole 500 mg PO bid for 7 days
  • Metronidazole gel 0.75% 5 g (one full applicator) intravaginally once daily for 5 days
  • Clindamycin 2% cream 5 g (one full applicator) intravaginally at bedtime for 7 days
• Alternatives:
  • Clindamycin 300 mg PO bid for 7 days
  • Clindamycin ovule (vaingal suppository) 100 mg intravaginally daily for 3 days
  • Tinidazole 2 g PO daily for 2 days
  • Tinidazole 1 g PO daily for 5 days

Pregnant Women

• Metronidazole 500 mg PO bid for 7 days
• Metronidazole 250 mg PO tid for 7 days
• Clindamycin 300 mg PO bid for 7 days