What is the best treatment for a patient with a respiratory tract infection, considering potential bacterial cause, antibiotic resistance, and underlying conditions like asthma or COPD?

Management of Respiratory Tract Infections

For lower respiratory tract infections in primary care, amoxicillin or tetracycline should be your first-line antibiotic choice, but only prescribe antibiotics when specific criteria are met—not for all respiratory infections. 1

Initial Assessment and Diagnosis

Distinguish Between Upper and Lower Respiratory Tract Infections

• Upper respiratory tract infections (URIs) including common cold, viral rhinitis, and uncomplicated pharyngitis are predominantly viral and do not require antibiotics 2, 3
• Lower respiratory tract infections (LRTIs) require more careful assessment to determine if antibiotics are indicated 1

Suspect Pneumonia When:

• Acute cough is present plus one or more of the following: new focal chest signs, dyspnea, tachypnea, or fever lasting >4 days 1, 4
• Obtain a chest radiograph to confirm pneumonia diagnosis before initiating treatment 1

When to Prescribe Antibiotics

For COPD Exacerbations - Use Anthonisen Criteria:

Prescribe antibiotics when patients have:

• Type I exacerbation: All three cardinal symptoms present—increased dyspnea, increased sputum volume, AND increased sputum purulence 1, 5
• Type II exacerbation with purulence: Two of the three symptoms, with increased sputum purulence being one of them 1, 4
• Severe exacerbations requiring invasive or non-invasive mechanical ventilation 1
• Patients with severe COPD (FEV1 <30%) even with fewer symptoms 1, 5

Do NOT prescribe antibiotics for:

• Type II exacerbations without purulence or Type III exacerbations (one or fewer symptoms) 1

For Other LRTI Situations:

Consider antibiotics in patients with:

• Suspected or confirmed pneumonia 1
• Age >75 years with fever 1
• Cardiac failure with respiratory symptoms 1
• Insulin-dependent diabetes mellitus with respiratory infection 1
• Serious neurological disorders (stroke, etc.) with respiratory symptoms 1

First-Line Antibiotic Selection

Standard LRTI Without Risk Factors:

• Amoxicillin 500-1000 mg three times daily OR tetracycline (doxycycline) 100 mg twice daily 1, 5, 6
• These are recommended based on least chance of harm and wide clinical experience 1, 6
• Doxycycline is particularly suitable for patients with renal impairment as it requires no dose adjustment 5

Alternative Options:

• For penicillin allergy: Macrolides (azithromycin, clarithromycin, erythromycin, or roxithromycin) in regions with low pneumococcal macrolide resistance 1, 4, 6
• For moderate-severe COPD exacerbations requiring hospitalization: Co-amoxiclav (amoxicillin-clavulanate) 1
• When first-line agents show high local resistance: Levofloxacin or moxifloxacin 1

Special Consideration: Pseudomonas aeruginosa Risk

Identify High-Risk Patients (Need ≥2 of the Following):

• Recent hospitalization 1, 5
• Frequent antibiotics (>4 courses per year) or recent use (last 3 months) 1, 5
• Severe COPD (FEV1 <30%) 1, 5
• Oral steroid use (>10 mg prednisolone daily in last 2 weeks) 1, 5

For Patients with P. aeruginosa Risk Factors:

• Oral route: Ciprofloxacin OR levofloxacin 750 mg/24h or 500 mg twice daily 1, 5
• Parenteral route: Ciprofloxacin OR β-lactam with antipseudomonal activity; aminoglycosides are optional 1
• Obtain sputum cultures before starting antibiotics in these patients 1

Treatment Duration and Monitoring

Duration:

• 5-7 days for most LRTI cases with clinical signs of bacterial infection 5, 4, 6
• Continue until clinical improvement is observed 5

Expected Response:

• Clinical improvement should occur within 3 days of starting antibiotics 1, 5, 4, 6
• Instruct patients to contact you if no improvement is noticeable within this timeframe 1, 5, 4

Follow-Up Instructions for Patients:

• Return if symptoms take >3 weeks to disappear 1, 4
• Contact immediately if: fever exceeds 4 days, dyspnea worsens, patient stops drinking, or consciousness decreases 1, 4
• Reassess seriously ill patients within 2 days (those with high fever, tachypnea, dyspnea, relevant comorbidity, or age >65 years) 1, 4

Route of Administration

• Switch from IV to oral by day 3 if patient is clinically stable 1
• Use oral or IV route based on clinical stability and exacerbation severity 1

Management of Treatment Failure

If No Response After 3 Days:

• Re-evaluate for non-infectious causes: inadequate medical treatment, pulmonary embolism, cardiac failure 1
• Obtain microbiological reassessment: sputum cultures or endotracheal aspirates 1
• Change to antibiotic with coverage against P. aeruginosa, resistant S. pneumoniae, and non-fermenters 1
• Adjust treatment according to culture results 1

Hospital Admission Criteria

Consider hospitalization for:

• Severely ill patients with suspected pneumonia (tachypnea, tachycardia, hypotension, confusion) 1
• Pneumonia patients failing outpatient antibiotic treatment 1
• Elderly patients with pneumonia and elevated complication risk (diabetes, heart failure, moderate-severe COPD, liver/renal disease, malignancy) 1
• Suspected pulmonary embolism or lung malignancy 1

Critical Pitfalls to Avoid

• Do NOT prescribe antibiotics for simple viral URIs, common cold, influenza, or uncomplicated acute bronchitis 2, 3, 7
• Do NOT use prophylactic antibiotics routinely in COPD or chronic bronchitis patients 1, 4
• Do NOT prescribe cough suppressants, expectorants, mucolytics, antihistamines, or bronchodilators for acute LRTI in primary care 1
• Always consider local antibiotic resistance patterns when selecting empiric therapy 1, 5, 4
• Do NOT prescribe antibiotics for all COPD exacerbations—use the Anthonisen criteria to determine appropriateness 5, 4, 6

Symptomatic Treatment

• For dry, bothersome cough: Dextromethorphan or codeine may be prescribed 1
• For pain or fever: Acetaminophen, ibuprofen, or naproxen 3
• Avoid expectorants, mucolytics, antihistamines, and bronchodilators in acute LRTI 1