In a 51‑year‑old adult with several days of nasal swelling, purulent yellow drainage, mild facial pain (4/10), no fever or chills, and a penicillin allergy, what microbiologic specimen should be obtained and what empiric antibiotic regimen should be initiated?

Acute Bacterial Sinusitis with Penicillin and Bactrim Allergy

Diagnostic Testing

Do not obtain any microbiologic specimens or imaging studies for this patient. 1

• Routine sinus cultures, nasal swabs, or antral puncture are not indicated for uncomplicated acute bacterial sinusitis in outpatient settings. 1
• CT imaging or plain radiographs should not be obtained unless you suspect complications (orbital cellulitis, meningitis, intracranial abscess) or an alternative diagnosis—neither of which this patient exhibits. 1
• Approximately 87% of viral upper respiratory infections show sinus abnormalities on imaging, making radiographic findings unreliable for distinguishing bacterial from viral disease. 1
• This patient meets clinical criteria for acute bacterial rhinosinusitis based on persistent purulent drainage and facial pain for several days without fever, making empiric antibiotic therapy appropriate without confirmatory testing. 1

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Antibiotic Selection

Prescribe a respiratory fluoroquinolone—specifically levofloxacin 500 mg once daily for 10 days or moxifloxacin 400 mg once daily for 10 days. 1, 2, 3

Why Fluoroquinolones Are the Correct Choice

• With documented allergies to both penicillin and trimethoprim-sulfamethoxazole (Bactrim), second- and third-generation cephalosporins carry a 1–10% cross-reactivity risk with penicillin and should be avoided unless the penicillin allergy is confirmed as non-severe (non-type I). 1, 2
• Respiratory fluoroquinolones provide 90–92% predicted clinical efficacy against all three major sinusitis pathogens: Streptococcus pneumoniae (including multidrug-resistant strains), Haemophilus influenzae (including β-lactamase producers), and Moraxella catarrhalis. 1, 2, 3
• Levofloxacin 500 mg daily for 10–14 days or moxifloxacin 400 mg daily for 10 days are the guideline-recommended regimens for patients with severe penicillin allergy. 1, 2

Alternative: Doxycycline (Suboptimal)

• Doxycycline 100 mg once daily for 10 days is an acceptable but inferior alternative, with only 77–81% predicted efficacy and a 20–25% bacteriologic failure rate due to limited activity against H. influenzae. 1, 2, 4
• Reserve doxycycline only if fluoroquinolones are contraindicated (e.g., pregnancy, tendon disorders, QT prolongation risk). 1, 2

What NOT to Prescribe

• Azithromycin or clarithromycin: Resistance rates exceed 20–25% for both S. pneumoniae and H. influenzae, making macrolides unsuitable. 1, 2, 5
• Trimethoprim-sulfamethoxazole (Bactrim): Already documented allergy, plus 50% resistance in S. pneumoniae and 27% in H. influenzae. 1, 2
• First-generation cephalosporins (cephalexin): Inadequate coverage—approximately 50% of H. influenzae strains produce β-lactamase. 2

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Essential Adjunctive Therapies (Add to All Patients)

Prescribe intranasal corticosteroids, saline irrigation, and analgesics regardless of antibiotic choice—these significantly improve symptom resolution. 1, 2, 6

• Intranasal corticosteroids (mometasone, fluticasone, or budesonide) twice daily reduce mucosal inflammation and accelerate recovery; supported by strong evidence from multiple randomized controlled trials. 1, 2, 6
• Saline nasal irrigation 2–3 times daily provides symptomatic relief and clears purulent secretions. 1, 2, 6
• Analgesics (acetaminophen or ibuprofen) for facial pain control—this patient rates pain 4/10, warranting scheduled dosing. 1, 2, 6
• Adequate hydration and warm facial compresses as supportive measures. 2

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Monitoring and Reassessment Protocol

Reassess this patient at 3–5 days after starting antibiotics; lack of improvement warrants immediate antibiotic switch or diagnostic re-evaluation. 1, 2

Day 3–5 Reassessment

• If no improvement (persistent purulent drainage, facial pain unchanged, or worsening symptoms): switch to high-dose amoxicillin-clavulanate 875 mg/125 mg twice daily if the penicillin allergy is confirmed as non-severe, or consider alternative fluoroquinolone if already on one. 1, 2
• If worsening at any time (increasing pain, fever, periorbital swelling, visual changes, severe headache, altered mental status): immediately evaluate for complications (orbital cellulitis, meningitis, intracranial abscess) and refer urgently to otolaryngology. 1, 2

Day 7 Reassessment

• If symptoms persist or worsen by day 7: reconfirm the diagnosis, exclude alternative etiologies (fungal sinusitis, anatomic obstruction, immunodeficiency), and obtain CT imaging only if complications are suspected. 1, 2
• Most patients (73–85%) show clinical improvement by day 7 even with placebo, so persistent symptoms at this point suggest treatment failure or misdiagnosis. 1

Expected Timeline for Improvement

• Most patients experience noticeable improvement within 3–5 days of appropriate antibiotic therapy. 1, 2
• Complete resolution typically occurs by 10–14 days or when symptom-free for 7 consecutive days. 1, 2
• Only 30–41% of patients improve by days 3–5, so lack of complete resolution at this early point does not necessarily indicate failure—but zero improvement does. 1

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Treatment Duration

Continue levofloxacin or moxifloxacin for a full 10 days, or until symptom-free for 7 consecutive days (typically 10–14 days total). 1, 2, 3

• Shorter 5-day courses of levofloxacin 750 mg daily are FDA-approved for acute bacterial sinusitis and provide comparable efficacy, but the 10-day 500 mg regimen remains standard. 3
• Ensure the minimum 10-day duration to prevent relapse—inadequate treatment duration is a common pitfall. 1, 2

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Critical Pitfalls to Avoid

• Do not use cephalosporins without confirming the type of penicillin allergy. If the patient has a history of anaphylaxis, urticaria, or angioedema with penicillin, cephalosporins carry significant cross-reactivity risk. 1, 2
• Do not prescribe antibiotics based solely on purulent nasal discharge. This patient meets criteria for bacterial sinusitis (persistent symptoms ≥7 days with purulent drainage and facial pain), but approximately 98–99.5% of acute rhinosinusitis is viral and resolves spontaneously within 7–10 days. 1, 2, 7
• Do not delay reassessment beyond 3–5 days. Early identification of treatment failure prevents complications and unnecessary prolonged courses of ineffective antibiotics. 1, 2
• Counsel patients on fluoroquinolone-associated risks: tendon rupture (especially in patients >60 years, on corticosteroids, or with renal disease), QT prolongation, and photosensitivity. 1, 2

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When to Refer to Otolaryngology

Refer immediately if any of the following occur: 1, 2

• No improvement after 7 days of appropriate fluoroquinolone therapy.
• Worsening symptoms at any time during treatment.
• Suspected complications: severe headache, visual changes, periorbital swelling/erythema, proptosis, diplopia, altered mental status, or cranial nerve deficits.
• Recurrent sinusitis (≥3 episodes per year) requiring evaluation for underlying allergic rhinitis, immunodeficiency, or anatomic abnormalities.

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Summary Algorithm

1. Confirm diagnosis: Persistent purulent nasal drainage + facial pain ≥7 days without fever = acute bacterial sinusitis. 1
2. No testing needed: Skip cultures and imaging unless complications suspected. 1
3. Prescribe levofloxacin 500 mg daily × 10 days (or moxifloxacin 400 mg daily × 10 days) due to penicillin and Bactrim allergies. 1, 2, 3
4. Add adjunctive therapies: Intranasal corticosteroids twice daily, saline irrigation 2–3 times daily, and scheduled analgesics. 1, 2, 6
5. Reassess at 3–5 days: Switch antibiotics if no improvement; evaluate urgently if worsening. 1, 2
6. Reassess at 7 days: Persistent symptoms warrant diagnostic re-evaluation and possible ENT referral. 1, 2