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, Porphyromonas, Bacteroides, Peptostreptococcus, Mycoplasma hominis, Ureaplasma urealyticum, Mobiluncus, Megasphaera, Clotridiales, Fusobacterium, and Atopobium

Pathophysiology

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

Clinical Manifestations

• Common cause of vaginal discharge, classically copious thin, grey discharge

Prognosis and Complications

• About 30% will relapse within 3 months, and 50% within 12 months

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

Relapse and Recurrence

• Symptomatic relapses can be treated with recurrent 7-day courses of oral metronidazole or clindamycin
• Can also consider boric acid vaginal suppositories for 30 days, either before or after oral treatment
  • Avoid if pregnant
  • Keep out or reach of children (can cause death if ingested)
  • May cause skin irritation in sexual partners
• Chronic suppressive therapy can be offere to patients with more than 3 documented episodes of BV within 12 months
  • Metronidazole 0.75% vaginal gel is preferred, twice weekly for 4 to 6 months
  • Can be preceded by metronidazole oral induction for 7 to 10 days
  • Decreases 12-month recurrence from 60% to 26%, though can cause vaginal candidiasis
• Adjunctive therapy:
  • Abstinence or condom use
  • Lactobacillus crispatus vaginal suppositories has some promise
• Avoid: vaginal acidifying agents and general probiotics