Bacterial Vaginosis (BV)
A PAP smear showing a shift in vaginal flora to coccobacilli with conspicuous absence of lactobacilli indicates bacterial vaginosis (BV), a polymicrobial condition characterized by replacement of normal hydrogen peroxide-producing Lactobacillus species with high concentrations of anaerobic bacteria, Gardnerella vaginalis, and Mycoplasma hominis. 1, 2
Diagnostic Interpretation
This PAP smear finding represents one component of the diagnostic criteria for BV:
The presence of clue cells (vaginal epithelial cells with bacteria adhered to their surface, creating a stippled appearance with obscured borders) is the key microscopic finding that confirms BV when combined with clinical criteria 1
The CDC recommends formal diagnosis using Amsel criteria, requiring three of four findings: homogeneous white non-inflammatory discharge adhering to vaginal walls, clue cells on microscopy, vaginal pH >4.5, and fishy odor before or after 10% KOH addition (whiff test) 1, 2
The shift from lactobacilli to coccobacilli reflects the fundamental pathophysiology—replacement of protective aerobic lactobacilli with predominantly anaerobic flora including Gardnerella, Prevotella, Peptostreptococcus, and Mobiluncus species 3, 4
Important Diagnostic Caveats
The CDC explicitly warns against diagnosing BV without clue cells unless confirmed by Gram stain, as this may lead to treating the wrong condition 1. A PAP smear alone showing bacterial shift is insufficient for definitive diagnosis:
If clue cells are not clearly documented on the PAP smear, confirm diagnosis with quantitative Gram stain using Nugent criteria (90% sensitivity), which is the most specific diagnostic method 1, 5
Standard clinical testing misses 20-30% of BV cases, making Gram stain with Nugent scoring essential when wet mount or PAP findings are equivocal 5
The IDSA recommends against treating asymptomatic patients with incidental bacterial findings and no clue cells, as this leads to inappropriate antibiotic use 1, 5
Clinical Significance and Associated Risks
BV is not a benign finding, even when asymptomatic:
Up to 50% of women with BV meeting diagnostic criteria are asymptomatic, meaning the infection can be present without classic symptoms 5, 2
BV increases risk for post-procedure infections following invasive gynecological procedures, making pre-operative identification critical 1
Treatment with metronidazole before surgical abortion substantially reduces post-abortion pelvic inflammatory disease 1
In pregnant women with history of preterm delivery, identifying and treating BV may reduce preterm birth risk 1
BV is associated with increased susceptibility to sexually transmitted infections including HIV, and can lead to pelvic inflammatory disease 2, 6
Treatment Recommendations
The CDC recommends treating symptomatic BV with metronidazole 500 mg orally twice daily for 7 days (cure rate 95%), with the principal goal being relief of vaginal symptoms 1, 5:
The 7-day regimen has superior cure rates (95%) compared to single-dose metronidazole 2g (84%) 1, 5
Alternative regimens include clindamycin, though metronidazole remains first-line 2, 3
Tinidazole 2g once daily for 2 days or 1g once daily for 5 days demonstrated therapeutic cure rates of 27.4% and 36.8% respectively versus 5.1% for placebo in FDA-approved studies 7
Recurrence and Long-Term Management
BV has a high recurrence rate of 50-80% within one year, which necessitates patient counseling 1, 5, 2:
Treating male sexual partners does not prevent BV recurrence 2
Probiotics as complementary therapy with antibiotics can improve cure rates (risk ratio 1.53,95% CI 1.19-1.97), particularly when combining metronidazole with probiotics 2
Recurrent cases may require repeated evaluations with clue cell identification and consideration of Gram stain confirmation 1