Residency · Residency · Family Medicine

Acute Respiratory Infections: Antibiotics Stewardship

Overview

Acute respiratory infections are the most common reason for outpatient antibiotic prescribing, yet the vast majority are viral and self-limited. Up to 50% of antibiotic prescriptions for these infections are inappropriate, contributing to antimicrobial resistance, adverse drug events, and unnecessary healthcare costs. Effective stewardship means knowing when antibiotics help, when they cause net harm, and how to communicate these decisions to patients who may expect a prescription.

Acute Pharyngitis

Etiology

Viral causes account for 70 to 85% of pharyngitis cases, including rhinovirus, adenovirus, EBV, influenza, parainfluenza, and COVID-19. Group A Streptococcus (GAS) is responsible for only 5 to 15% of adult pharyngitis and 15 to 30% in children. Other bacterial pathogens include Group C/G Streptococcus, Fusobacterium necrophorum (associated with peritonsillar abscess and Lemierre syndrome), and Neisseria gonorrhoeae.

Diagnosis

The Centor/McIsaac criteria guide clinical decision-making. Points are assigned for tonsillar exudates, tender anterior cervical lymphadenopathy, fever above 38 degrees Celsius, and absence of cough, with an age modifier (plus 1 for ages 3 to 14, minus 1 for age 45 and above). A score of 0 to 1 warrants neither testing nor antibiotics. A score of 2 to 3 prompts a rapid antigen detection test (RADT) or culture, with treatment only if the result is positive. A score of 4 or above may justify empiric treatment while awaiting results. RADT sensitivity ranges from 86 to 95%. In children, a negative RADT should be confirmed with a backup throat culture. In adults, a negative RADT is sufficient to withhold antibiotics.

Treatment of GAS Pharyngitis

Penicillin V at 500 mg two to three times daily for 10 days remains first-line, as there is no GAS resistance to penicillin. Amoxicillin at 50 mg/kg/day (maximum 1000 mg) for 10 days is preferred in children due to better taste. For penicillin-allergic patients, cephalexin (if no anaphylaxis history), azithromycin (5 days), or clindamycin are alternatives. The primary benefit of antibiotics is prevention of rheumatic fever, with a modest reduction in symptom duration of approximately one day.

Complications

Peritonsillar abscess presents with unilateral swelling, uvular deviation, trismus, and a "hot potato" voice. Lemierre syndrome involves septic thrombophlebitis of the internal jugular vein caused by Fusobacterium necrophorum. Post-streptococcal glomerulonephritis is not prevented by antibiotic treatment.

Acute Rhinosinusitis

Diagnosis

Most cases are viral and resolve within 10 days. Bacterial sinusitis should be suspected when any one of the following is present: symptoms lasting 10 days or more without improvement, severe onset with fever of 39 degrees Celsius or above with purulent nasal discharge for three to four days, or "double worsening" where initial improvement is followed by new fever or worsening symptoms. Imaging is not recommended for uncomplicated acute sinusitis, as incidental mucosal changes on CT are extremely common and present in up to 40% of asymptomatic adults. Purulent nasal discharge alone does not indicate bacterial infection.

Treatment

Viral sinusitis is managed with supportive care: nasal saline irrigation (which has strong evidence), intranasal corticosteroids, analgesics, and short-term decongestants. For bacterial sinusitis, watchful waiting is appropriate for mild-to-moderate symptoms, with reassessment in seven days. When antibiotics are indicated, amoxicillin-clavulanate at 875/125 mg twice daily for five to seven days is first-line. Amoxicillin alone should be avoided because 30% of Haemophilus influenzae produce beta-lactamase. For penicillin-allergic patients, doxycycline or a respiratory fluoroquinolone (reserved for true allergy) are alternatives. Five to seven days of treatment is sufficient for uncomplicated cases.

Red Flags Requiring Urgent Referral

Periorbital edema or erythema suggesting orbital cellulitis, visual changes, severe headache, or altered mental status suggesting intracranial extension, and high fever unresponsive to appropriate antibiotics all warrant urgent referral.

Acute Bronchitis

Key Principle: Antibiotics Are Almost Never Indicated

Acute bronchitis causes cough lasting up to three weeks, often with sputum production, and is viral in over 90% of cases. Green or yellow sputum does not indicate bacterial infection; it reflects neutrophilic inflammation, which occurs with viral infections as well. Antibiotics should not be prescribed for acute bronchitis in otherwise healthy adults.

Management

Symptomatic treatment includes dextromethorphan, honey (which has evidence in both children and adults), and guaifenesin (with weak evidence). A short-acting beta-agonist inhaler trial may help patients with wheezing or airflow obstruction. Patient expectations should be addressed directly: the natural history of a cough from bronchitis averages 18 days, and antibiotics do not shorten the course. The delayed prescribing strategy, in which a prescription is provided with instructions to fill only if symptoms worsen after five to seven days, reduces antibiotic use by approximately 50%. Pneumonia should be suspected if fever above 38 degrees Celsius persists beyond three to four days, or if tachycardia, tachypnea, focal lung findings, or hypoxia are present.

Community-Acquired Pneumonia (CAP)

Diagnosis

CAP requires a new radiographic infiltrate plus clinical features such as cough, fever, dyspnea, or pleuritic chest pain. Auscultation may reveal crackles, bronchial breath sounds, or egophony. Laboratory evaluation includes CBC (for leukocytosis), CRP, and procalcitonin (a low level below 0.25 ng/mL supports withholding antibiotics and suggests viral etiology). Chest X-ray is required for diagnosis, with CT considered when clinical suspicion is high but X-ray is negative. Sputum culture is reserved for inpatients or treatment failures.

Outpatient Treatment (Otherwise Healthy, No Comorbidities)

Amoxicillin at 1 gram three times daily for five days is first-line per ATS/IDSA 2019 guidelines, providing adequate pneumococcal coverage. Doxycycline at 100 mg twice daily for five days is an alternative that also covers atypical organisms. Azithromycin (500 mg day one, 250 mg days two through five) should only be used if local pneumococcal resistance is below 25%.

Outpatient Treatment (With Comorbidities)

For patients with diabetes, heart, lung, liver, or renal disease, alcoholism, immunosuppression, or recent antibiotic use, the recommended regimen is amoxicillin-clavulanate or cefpodoxime plus a macrolide or doxycycline, or a respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) for five days. Fluoroquinolones should be reserved for patients with true beta-lactam allergy or treatment failure.

Duration of Therapy

Five days is sufficient for uncomplicated CAP, supported by multiple studies showing non-inferiority to seven-to-ten day courses. Minimum criteria before stopping include being afebrile for 48 hours, clinically improving, and tolerating oral intake. Seven days is appropriate for complicated or severe CAP.

Hospitalization Criteria

The CURB-65 score (Confusion, Urea above 7 mmol/L, Respiratory rate 30 or above, Blood pressure below 90/60, Age 65 or above) helps guide disposition. A score of 0 to 1 supports outpatient treatment, 2 suggests considering a short admission, and 3 to 5 indicates inpatient management with ICU consideration at 4 to 5. Clinical judgment should override scores when appropriate.

Antibiotic Stewardship Strategies

Communication Techniques

Naming the illness with a positive diagnosis ("You have a viral upper respiratory infection") is more effective than simply saying what the patient does not have. Explaining why antibiotics will not help and may cause harm (including side effects and contribution to resistance) provides honest education. Providing a contingency plan with specific symptoms that should prompt return addresses the patient's underlying anxiety. Acknowledging the patient's suffering and offering symptomatic management validates their experience.

Delayed Prescribing

Providing an antibiotic prescription with instructions to fill only if symptoms are not improving in 48 to 72 hours is a validated strategy that reduces antibiotic use by approximately 50% without increasing complications or reducing patient satisfaction.

Procalcitonin-Guided Therapy

Low procalcitonin (below 0.25 ng/mL) supports withholding or discontinuing antibiotics and is most useful for lower respiratory tract infections. The ProACT and PRORATA trials demonstrated that procalcitonin-guided therapy reduces antibiotic exposure without worsening outcomes.

Institutional Strategies

Local antibiograms guide empiric therapy based on community resistance patterns. Audit and feedback systems that compare prescribing rates among providers, clinical decision support in the EHR, and patient education materials in waiting rooms all contribute to a culture of appropriate prescribing.

<image>A clinical decision support infographic for the four major acute respiratory infections (pharyngitis, sinusitis, bronchitis, pneumonia) showing for each condition: when antibiotics ARE and ARE NOT indicated, first-line antibiotic choice and duration, key diagnostic criteria, and common stewardship pitfalls. Use a traffic-light color system (green = no antibiotics, yellow = conditional, red = antibiotics indicated).</image>

<image>A Centor/McIsaac scoring tool visual showing each criterion with icons (tonsillar exudates, lymphadenopathy, fever thermometer, absence of cough stethoscope, age modifier), the scoring total, and the recommended action for each score range (0-1: no test, 2-3: RADT then treat if positive, 4+: RADT and consider empiric treatment).</image>

<image>A patient-facing educational handout explaining why antibiotics are not needed for viral respiratory infections, showing the natural timeline of cold and bronchitis symptoms (cough lasting 2-3 weeks is normal), effective symptom management strategies, and specific warning signs that should prompt return for re-evaluation. Design with clear icons and minimal medical jargon.</image>

Clinical Pearls

Green or yellow sputum does not indicate bacterial infection; it reflects neutrophilic inflammation that occurs with viral infections just as readily. Acute bronchitis is the single most common condition for which antibiotics are inappropriately prescribed, and the urge to prescribe must be actively resisted. Delayed prescribing is a validated approach that maintains patient satisfaction while halving unnecessary antibiotic use. Five days of antibiotics for uncomplicated CAP is sufficient; traditional 10 to 14 day courses are unnecessarily long. Amoxicillin for outpatient pneumonia should be dosed at 1 gram three times daily, not the standard 500 mg, to ensure adequate pneumococcal coverage. Imaging is not indicated for uncomplicated acute sinusitis. A Centor/McIsaac score of 0 to 1 should not prompt strep testing, as the pretest probability is too low and testing in this population increases false-positive-driven overtreatment. Every unnecessary antibiotic prescription carries real risks: Clostridioides difficile infection, allergic reactions, drug interactions, and contribution to community antimicrobial resistance.

References

• Harris AM et al. Appropriate Antibiotic Use for Acute Respiratory Tract Infection in Adults. Ann Intern Med. 2016
• Shulman ST et al. IDSA Guidelines for GAS Pharyngitis. Clin Infect Dis. 2012
• Rosenfeld RM et al. AAO-HNS Clinical Practice Guideline: Adult Sinusitis. Otolaryngol Head Neck Surg. 2015
• Metlay JP et al. ATS/IDSA Guidelines for CAP in Adults. Am J Respir Crit Care Med. 2019
• Spurling GK et al. Delayed Antibiotics for Respiratory Infections. Cochrane Database Syst Rev. 2017
• Ebell MH et al. Duration of Antibiotic Therapy for CAP. Ann Intern Med. 2023

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