Viral Swab for Draining Pustular Finger Infection
A viral swab is not indicated for this presentation—this is almost certainly a bacterial infection, most likely Staphylococcus aureus, and you should obtain a bacterial culture and sensitivity testing instead. 1
Why This Is Bacterial, Not Viral
A draining pustular lesion that has failed fusidic acid (Fucidine) cream strongly suggests:
- Bacterial infection (purulent drainage is the hallmark)
- Possible fusidic acid resistance in S. aureus (resistance rates in dermatology patients can reach 50-78%, particularly with prior topical fusidic acid use) 2, 3
- Alternative bacterial pathogens that are not covered by fusidic acid
Viral infections of the finger (such as herpetic whitlow from HSV) typically present with:
- Grouped vesicles on an erythematous base
- Clear fluid initially (not purulent drainage)
- Severe pain out of proportion to findings
- No response to antibiotics (which would be expected)
Your patient has a pustule with drainage—this is bacterial until proven otherwise.
What You Should Do Instead
1. Obtain Bacterial Culture and Sensitivity
Gram stain and culture of the purulent drainage are recommended 1. This will:
- Identify the causative organism (S. aureus, streptococci, or other bacteria)
- Determine antibiotic susceptibilities, including fusidic acid resistance
- Guide definitive therapy
2. Incision and Drainage
If there is an abscess or significant purulent collection, incision and drainage is the primary treatment 1. This is more important than antibiotics alone for localized purulent infections.
3. Empiric Antibiotic Coverage
While awaiting culture results, consider oral antibiotics active against S. aureus:
- If MRSA suspected or high local prevalence: doxycycline, clindamycin, or trimethoprim-sulfamethoxazole 1
- If MSSA likely: dicloxacillin or cephalexin 1
- Duration: 7 days for simple skin infections 1
Given the failure of topical fusidic acid, resistance is likely 2, 3, so switching to a different antibiotic class is prudent.
4. Systemic Signs Assessment
Evaluate for:
- Temperature >38.5°C
- Heart rate >110 bpm
- Erythema extending >5 cm from the lesion
- Lymphangitis or lymphadenopathy
These findings would warrant more aggressive systemic antibiotic therapy 1.
Common Pitfalls
- Don't assume viral: Pustular drainage = bacterial infection
- Don't continue ineffective topical therapy: Fusidic acid resistance is common in dermatology patients, especially with prior use 2, 3
- Don't forget drainage: Antibiotics alone are insufficient for abscesses 1
- Don't overlook rare organisms: If standard therapy fails, consider atypical bacteria like Streptococcus gordonii (though rare) 4
When to Consider Viral Testing
You would consider HSV testing (viral culture or PCR) only if the presentation included:
- Grouped vesicles (not pustules)
- Clear fluid
- Severe pain
- History of recurrent similar lesions
- Immunocompromised status
In your case, proceed with bacterial culture, not viral swab.