What type of pneumonia is commonly caused in individuals with Human Immunodeficiency Virus (HIV)/Acquired Immunodeficiency Syndrome (AIDS)?

Pneumonia Types in HIV/AIDS Patients

Streptococcus pneumoniae and Haemophilus influenzae are the most common bacterial causes of pneumonia in HIV-infected patients, while Pneumocystis jirovecii pneumonia (PCP) is the most common opportunistic pneumonia in advanced HIV disease. 1, 2

Bacterial Pneumonia in HIV/AIDS

Common Bacterial Pathogens

• Streptococcus pneumoniae - Most frequent cause 1, 2
• Haemophilus influenzae - Second most common 1, 2
• Pseudomonas aeruginosa - More common in HIV than non-HIV patients 1
• Staphylococcus aureus - Increased frequency in HIV patients 1
• Atypical pathogens - Less common but important considerations:
  • Legionella pneumophila
  • Mycoplasma pneumoniae
  • Chlamydophila species 1

Risk Factors for Bacterial Pneumonia

• Low CD4+ count (especially <100 cells/μL) 1, 2
• Injection drug use 1
• Cigarette smoking 1
• Advanced HIV disease 1

Clinical Presentation of Bacterial Pneumonia

• Acute onset (3-5 days) 1
• Fever, chills, rigors 1
• Chest pain 1
• Productive cough with purulent sputum 1
• Dyspnea 1
• Focal consolidation on lung examination 1
• Unilateral, focal, segmental, or lobar consolidation on chest radiograph 1
• Elevated WBC count with left shift 1
• Higher risk of bacteremia compared to HIV-negative patients 1

Pneumocystis Jirovecii Pneumonia (PCP)

Clinical Significance

• Most common opportunistic pneumonia in HIV/AIDS 3
• Most common life-threatening infectious complication in HIV-infected patients 3
• Higher mortality (10-20%) during initial infection 4
• Mortality increases substantially with need for mechanical ventilation 4

Clinical Presentation of PCP

• Subacute onset with:
  • Progressive dyspnea
  • Non-productive cough
  • Fever
• Normal or inspiratory crackles on lung examination (contrasting with bacterial pneumonia) 1
• Diffuse, bilateral interstitial infiltrates on chest radiograph (different from typical bacterial pattern) 1

Diagnosis and Treatment of PCP

• First-line treatment: Trimethoprim-sulfamethoxazole (TMP-SMX) 3
• Adjunctive corticosteroids for moderate-to-severe cases (PaO2 <70 mmHg or A-a gradient >35 mmHg) 4
• Alternative treatments for TMP-SMX intolerance:
  • Pentamidine (IV or aerosolized)
  • Atovaquone
  • Clindamycin-primaquone
  • Trimethoprim-dapsone 5

Other Important Pneumonias in HIV/AIDS

Mycobacterial Pneumonia

• Mycobacterium tuberculosis - Always consider in HIV patients with pneumonia 1
• Higher risk in HIV patients compared to general population 1
• May present with atypical radiographic findings in advanced HIV 1

Diagnostic Approach

1. Chest radiograph - Essential for all suspected pneumonia cases 1, 2
2. Oxygen assessment - Pulse oximetry or arterial blood gas within 8 hours 2
3. Microbiological studies:
   • Sputum Gram stain and culture
   • Blood cultures (higher yield in HIV patients)
   • Acid-fast bacilli smear and culture
   • PCP staining
   • Fungal stain and culture 2
4. CD4+ count - Critical for risk stratification and treatment decisions 2

Treatment Considerations

Bacterial Pneumonia Treatment

• Outpatient: Oral beta-lactam plus oral macrolide 2
• Non-ICU inpatient: IV beta-lactam plus macrolide 2
• ICU treatment: IV beta-lactam plus either IV azithromycin or IV respiratory fluoroquinolone 2
• Penicillin allergy: Respiratory fluoroquinolone or aztreonam plus fluoroquinolone 2

PCP Treatment

• TMP-SMX remains first-line therapy 3
• Adjunctive corticosteroids for PaO2 <70 mmHg or A-a gradient >35 mmHg 4
• Monitor for adverse reactions, particularly rash, fever, leukopenia, and elevated transaminases, which occur more frequently in AIDS patients 6

Prevention Strategies

• Pneumococcal vaccination 2
• Annual influenza vaccination 2
• PCP prophylaxis when CD4 <200 cells/μL 2
• Smoking cessation 2
• Reduction of substance use 2
• Antiretroviral therapy to maintain immune function 1, 2

Common Pitfalls and Caveats

• Bacterial pneumonia may be the first manifestation of underlying HIV infection 1
• HIV patients have higher rates of bacteremia with pneumonia, especially with S. pneumoniae 1
• Drug-resistant S. pneumoniae is increasing and associated with higher mortality 1
• HIV patients may present with multifocal or multilobar involvement and parapneumonic effusions more frequently than HIV-negative patients 1
• Always consider tuberculosis in HIV patients with pneumonia 1
• Monitor for drug interactions between antibiotics and antiretroviral medications 2
• Consider immune reconstitution syndrome in patients starting or recently started on antiretroviral therapy 2