What are common questions about community-acquired pneumonia that seminar attendees may ask?

Common Questions About Community-Acquired Pneumonia for Seminars

Diagnostic Questions

How do you diagnose CAP and what imaging is required?

Diagnose CAP based on clinical signs/symptoms (new cough, dyspnea, fever >38°C or ≤36°C, leukocyte count abnormalities) plus radiographic confirmation with chest X-ray, though clinical diagnosis alone is acceptable in mild outpatient cases 1, 2. In elderly or immunocompromised patients, CAP may present atypically with confusion, failure to thrive, or falls rather than respiratory symptoms, but tachypnea is usually present 3.

• Chest radiography (PA and lateral views) is valuable for differentiating pneumonia from other conditions and identifying complications like pleural effusion, lung abscess, or multilobar involvement 3.
• Lung ultrasonography or CT can be used when chest X-ray is unavailable or equivocal 4.
• High-resolution CT may detect infiltrates in radiographically negative cases, though clinical relevance is uncertain 3.

What diagnostic tests should be ordered?

The testing strategy depends entirely on disease severity and care setting 1, 2:

Outpatients without severe disease:

• No routine sputum cultures, blood cultures, or urine antigen testing required 1, 2.
• Test for COVID-19 and influenza when these viruses are circulating in the community 5.
• Procalcitonin measurement is not recommended 4.

Hospitalized patients with non-severe CAP:

• Blood cultures prior to antibiotics 1.
• Sputum Gram stain and culture only if high-quality specimen can be rapidly processed 1.
• Urine antigens for pneumococcus and Legionella in select cases 1.

Severe CAP (ICU patients):

• Pretreatment sputum cultures, blood cultures, and urine antigens for pneumococcus and Legionella are mandatory 1, 2.
• Consider bronchoscopy with protected specimen brush for Gram stain and quantitative culture in nonresponding patients 3.

Can you distinguish bacterial from viral or atypical pneumonia clinically?

No—clinical characteristics cannot reliably establish specific etiological diagnosis with adequate sensitivity and specificity 2. The traditional "typical" versus "atypical" classification has limited clinical value because atypical pathogens (Mycoplasma, Chlamydia, Legionella) cause overlapping clinical manifestations with typical bacterial pathogens 2. Up to 50% of CAP patients never have a pathogen identified even with extensive testing 2. Only 38% of hospitalized CAP patients have a pathogen identified; of those, up to 40% have viruses and approximately 15% have Streptococcus pneumoniae 5.

Severity Assessment and Site of Care Questions

How do you decide who needs hospitalization versus outpatient treatment?

Use validated severity scores—PSI (Pneumonia Severity Index) or CURB-65 (Confusion, Urea, Respiratory rate, Blood pressure, age ≥65)—to determine hospitalization need 1, 2. CRB-65 (without laboratory testing) is well-validated for primary care settings 4. The hospitalization rate is approximately 2% in people 65 years or older, with 30-day mortality of 6% in hospitalized patients 4.

What defines severe CAP requiring ICU admission?

Severe CAP is defined by septic shock requiring vasopressors OR respiratory failure requiring mechanical ventilation 1, 2. Additional ICU admission criteria include 3:

• Three or more minor criteria: respiratory rate ≥30/min, PaO2/FiO2 ratio ≤250, multilobar infiltrates, confusion/disorientation, uremia, leukopenia, thrombocytopenia, hypothermia, hypotension requiring aggressive fluid resuscitation 3.
• ICU mortality for severe CAP is approximately 30%, with up to 50% mortality in those requiring mechanical ventilation 3.

What are the risk factors for severe CAP and mortality?

Age ≥65 years, COPD, chronic heart failure, diabetes mellitus, renal insufficiency/dialysis, malignancy, chronic liver disease/alcohol abuse, and immunosuppression are major risk factors 3. Additional mortality risk factors include 3:

• Male sex 3.
• Development of acute respiratory failure, severe sepsis/septic shock, or bacteremia 3.
• Multilobar consolidation 3.
• Specific pathogens: S. pneumoniae (most common lethal pathogen, responsible for two-thirds of CAP deaths), Pseudomonas aeruginosa, and Legionella pneumophila 3.

Treatment Questions

What is the empiric antibiotic regimen for outpatients?

For healthy outpatients without comorbidities: amoxicillin, doxycycline, or a macrolide (only in areas where pneumococcal resistance to macrolides is <25%) 1, 4.

For outpatients with comorbidities (COPD, diabetes, heart failure, chronic kidney disease, chronic liver disease, alcoholism, malignancy, asplenia):

• Amoxicillin/clavulanate or cephalosporin PLUS macrolide 1.
• OR respiratory fluoroquinolone monotherapy (levofloxacin, moxifloxacin) 1, 4.

What is the empiric antibiotic regimen for hospitalized patients?

For hospitalized patients with non-severe CAP: parenteral β-lactam (ceftriaxone 1g IV q24h or cefotaxime 1g IV q8h) PLUS macrolide (azithromycin 500mg IV/PO) 3, 1, 5. This combination has stronger evidence than β-lactam plus fluoroquinolone 2.

Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750mg IV/PO daily) 3, 6.

What is the empiric antibiotic regimen for severe CAP in the ICU?

For ICU patients WITHOUT Pseudomonas risk factors: IV β-lactam (cefotaxime, ceftriaxone, or cefuroxime) PLUS either IV macrolide (azithromycin) OR IV fluoroquinolone 3, 1.

For ICU patients WITH Pseudomonas risk factors (prior Pseudomonas infection, structural lung disease like bronchiectasis, recent hospitalization with IV antibiotics within past 90 days, chronic/prolonged broad-spectrum antibiotic therapy ≥7 days in past month):

• Antipseudomonal β-lactam (cefepime, imipenem, meropenem, or piperacillin/tazobactam) PLUS antipseudomonal quinolone (ciprofloxacin) 3, 2.
• OR antipseudomonal β-lactam PLUS aminoglycoside PLUS either macrolide or nonpseudomonal fluoroquinolone 3.

When should you add MRSA coverage?

Add MRSA coverage (vancomycin or linezolid) if the patient has prior MRSA infection, recent hospitalization with IV antibiotics, or high local MRSA prevalence 2. MRSA is one of the "PES" pathogens (Pseudomonas, ESBL-producing Enterobacteriaceae, MRSA) that account for up to 6% of hospitalized CAP 3.

How long should antibiotic therapy continue?

Minimum of 5 days for all patients, with clinical stability required before discontinuation 2. Clinical stability is defined as improvement of symptoms assessed at day 5-7 3. For severe CAP, assess response at day 2-3 (fever resolution, lack of progression of pulmonary infiltrates) 3. The 5-day levofloxacin 750mg regimen is equivalent to 10-day levofloxacin 500mg regimen for mild-to-severe CAP 6.

Should corticosteroids be used in CAP?

Systemic corticosteroid administration within 24 hours of severe CAP development may reduce 28-day mortality 5. However, corticosteroids should not be routinely used except in refractory septic shock or severe CAP 2. The evidence remains mixed, requiring case-by-case judgment 7, 8.

Microbiology Questions

What are the most common pathogens in CAP?

Streptococcus pneumoniae remains the most common bacterial pathogen regardless of age and comorbidities 3, 5. In ICU patients, the most common organisms are S. pneumoniae, Legionella pneumophila, and Haemophilus influenzae 3. Viral pathogens are identified in up to 40% of hospitalized CAP patients with identified etiology 5. Rhinovirus and influenza are common viral causes 7.

What pathogens should be considered in specific patient populations?

Patients with COPD: Consider Haemophilus influenzae, Moraxella catarrhalis, and Escherichia coli 7.

Aspiration risk (pulmonary abscess, cavitated pneumonia): Use amoxicillin-clavulanate 2g IV q6h or clindamycin 600mg IV q8h 3.

Immunocompromised patients: Require more extensive diagnostic approach including bronchoscopy with BAL for opportunistic pathogens 3, 9.

How common is drug-resistant Streptococcus pneumoniae (DRSP)?

Multi-drug resistant S. pneumoniae (MDRSP) isolates are resistant to ≥2 of the following: penicillin (MIC ≥2 mcg/mL), 2nd generation cephalosporins, macrolides, tetracyclines, and trimethoprim/sulfamethoxazole 6. Levofloxacin achieved 95% clinical and bacteriologic success in MDRSP CAP 6. Antipseudomonal agents (cefepime, piperacillin/tazobactam, imipenem, meropenem) are generally active against DRSP but not recommended for routine use unless Pseudomonas risk factors present 3.

Prevention Questions

What vaccinations are recommended for CAP prevention?

All adults ≥65 years or those 19-64 with underlying conditions should receive:

• 20-valent pneumococcal conjugate vaccine (PCV20) alone 4.
• OR 15-valent pneumococcal conjugate vaccine (PCV15) followed by 23-valent pneumococcal polysaccharide vaccine (PPSV23) one year later 4.
• The 13-valent pneumococcal conjugate vaccine (PCV13) is no longer recommended for routine administration 4.

Additional indications for pneumococcal vaccine: Cardiovascular disease, pulmonary disease, diabetes mellitus, alcoholism, liver cirrhosis, cerebrospinal fluid leaks, immunosuppression (HIV, chronic renal failure, organ transplant, hematologic malignancies, asplenia, sickle cell disease) 3.

Influenza vaccine: Recommended for all adults ≥65 years, those with chronic diseases, and medical/nursing home employees 3, 4.

COVID-19 vaccine: Recommended for all adults 4.

Management Pitfalls Questions

What are common pitfalls in CAP management?

Never delay antibiotics while pursuing diagnostic testing—empiric therapy must begin immediately 1, 2. Sputum Gram stain alone should not guide initial therapy 1. Do not use acute-phase reactants as sole determinants to distinguish viral from bacterial CAP 1.

Critical timing issues:

• Antibiotics should be initiated immediately upon diagnosis 2.
• For severe CAP, rapid ICU admission once diagnosis confirmed and initiate sepsis protocol 7.
• Time to first antibiotic dose correlates with mortality 8.

When should you investigate for nonresponding pneumonia?

Consider bronchoscopy with protected specimen brush, BAL (especially for opportunistic agents), detection of pneumococcal and Legionella antigens, and transbronchial or open lung biopsy when pneumonia is still unresolving 3. When cavitation or pleural effusion suspected, perform ultrasound ± CT ± needle aspiration with pleural fluid examination (pH, proteins, glucose, LDH, Gram stain, culture, pneumococcal antigen) 3.

Should follow-up chest X-rays be routine?

Do not perform routine follow-up chest radiographs in patients who achieve clinical stability 2. However, consider lung cancer screening if the patient meets eligibility criteria 2.