What is the recommended stepwise management of lower respiratory tract infection (LRTI) in adults, including assessment, supportive care, and antimicrobial therapy?

Management of Lower Respiratory Tract Infection (LRTI)

Initiate empirical antibiotic therapy immediately based on severity assessment and risk stratification, with amoxicillin as first-line for uncomplicated cases and amoxicillin-clavulanate for patients with risk factors. 1, 2

Initial Severity Assessment and Treatment Setting

Assess severity using clinical parameters to determine appropriate treatment location:

• Mild pneumonia: Manage outpatient with oral antibiotics from the start 3
• Moderate pneumonia: Consider hospitalization; sequential IV-to-oral therapy appropriate for most patients 3
• Severe pneumonia: Requires ICU admission and immediate parenteral antibiotics 3

Key severity markers requiring hospitalization include: respiratory rate ≥30 breaths/min, temperature <35°C or ≥40°C, heart rate ≥125 beats/min, blood pressure <90/60 mmHg, cyanosis, or altered mental status 2

For acute bronchitis without pneumonia: Do not prescribe antibiotics, as >90% of cases are viral and antibiotics provide no benefit 1. Pneumonia is unlikely if all of the following are absent: tachycardia, tachypnea, fever, and abnormal chest examination findings 1

Empirical Antibiotic Selection

First-Line Therapy for Uncomplicated LRTI

Amoxicillin 500-1000 mg every 8 hours for 5-7 days is the recommended first-choice agent for adults without risk factors 1, 2

When to Escalate to Amoxicillin-Clavulanate

Use amoxicillin-clavulanate instead of plain amoxicillin when ANY of the following risk factors are present: 1, 2

• Chronic lung disease (COPD, bronchiectasis)
• Recent antibiotic use (within last 3 months)
• High local prevalence of β-lactamase-producing Haemophilus influenzae
• Recent hospitalization
• Documented failure of aminopenicillin therapy

Alternative Regimens for Penicillin Allergy

For non-anaphylactic penicillin allergy: 2

• Oral cephalosporin (appropriate option)
• Tetracycline (doxycycline 100 mg twice daily, especially in smokers)

For true penicillin allergy: 1, 2

• Macrolide (clarithromycin 250-500 mg twice daily or azithromycin)
• Respiratory fluoroquinolones (levofloxacin, moxifloxacin) reserved for treatment failures or complicated infections

Treatment Duration and Route

Standard duration: 5-7 days for most community-acquired pneumonia 1, 2

Extended duration: 14 days for intracellular pathogens such as Legionella spp 3

IV-to-oral switch: Should occur by day 3 of admission if the patient is clinically stable, based on resolution of fever, respiratory parameters, and hemodynamic stability 3

Special Populations: COPD Exacerbations

Prescribe antibiotics for hospitalized COPD patients ONLY when: 3

1. Type I Anthonisen exacerbation: All three symptoms present (increased dyspnea, sputum volume, AND sputum purulence)
2. Type II Anthonisen exacerbation: Two symptoms present, with increased sputum purulence as one of them
3. Severe exacerbation requiring mechanical ventilation (invasive or non-invasive)

Do NOT prescribe antibiotics for: Type II exacerbations without purulence or Type III exacerbations (one or no cardinal symptoms) 3

Risk Factors for Pseudomonas aeruginosa in COPD

Consider P. aeruginosa coverage when at least TWO of the following are present: 3

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

For P. aeruginosa risk: Use ciprofloxacin (or levofloxacin 750 mg/24h or 500 mg twice daily) orally, or IV ciprofloxacin/antipseudomonal β-lactam when parenteral therapy needed 3

For standard COPD exacerbations without P. aeruginosa risk: Co-amoxiclav is recommended, with levofloxacin and moxifloxacin as alternatives 3

Microbiological Investigation

For hospitalized patients: Obtain sputum cultures or endotracheal aspirates (in mechanically ventilated patients) before starting antibiotics 3

For outpatients: Microbiological testing is generally not required for uncomplicated cases 3

Assessment of Treatment Response

Monitor response using clinical criteria: body temperature, respiratory rate, hemodynamic parameters 3

Re-evaluate at 48-72 hours if no clinical improvement to confirm diagnosis and exclude complications 3, 2

Non-response occurring in first 72 hours is usually due to antimicrobial resistance, unusually virulent organism, host defense defect, or wrong diagnosis 3

Non-response after 72 hours is usually due to a complication 3

Management of Treatment Failure

For unstable patients: Full reinvestigation followed by second empirical antimicrobial regimen covering P. aeruginosa, resistant S. pneumoniae, and non-fermenters 3

For stable patients with slow resolution: Reinvestigation may be withheld; manage according to clinical condition and individual risk factors 3

Re-evaluate non-infectious causes: inadequate medical treatment, pulmonary embolism, cardiac failure, before changing antibiotics 3

Supportive Care

For acute bronchitis with wheezing: Consider β-agonists (albuterol) only if wheezing present and underlying airflow obstruction exists 1

Symptomatic relief options: Cough suppressants, expectorants, first-generation antihistamines, decongestants 1

For severe cases: Low molecular weight heparin indicated in patients with acute respiratory failure; consider non-invasive ventilation particularly in COPD patients 3

Critical Pitfalls to Avoid

Do not prescribe antibiotics based on phlegm color alone – this leads to the highest rate of inappropriate prescribing among all acute respiratory tract infections 1

Do not use macrolides (azithromycin) for acute bronchitis – they increase adverse events without benefit 1

Do not assume crackles always indicate pneumonia – use full clinical criteria to distinguish bronchitis from pneumonia 1

Do not order chest X-rays for uncomplicated bronchitis – testing only indicated if pneumonia is suspected 1

Do not use cefuroxime as automatic first-line therapy in patients with chronic lung disease or recent antibiotic exposure; amoxicillin-clavulanate is superior 2

Do not use oral cephalosporins when β-lactamase-producing organisms are suspected 2

Do not give prophylactic antibiotics for prevention in chronic bronchitis or COPD 3