Aetiology of VAP in patients with immune compromise
Patients with immune compromise are at greater risk of pneumonia than people who are not immunocompromised. Patients with immune compromise include those:
- with neutropenia
- with immunodeficiency disorders
- with advanced human immunodeficiency virus (HIV) infection
- with haematological malignancies
- receiving immunosuppressive therapy or chemotherapy.
Although a broad range of pathogens can cause VAP in patients with immune compromise, the most common pathogens are the same as in patients without immune compromise (eg gram-negative bacteria).
Note: Even in patients with immune compromise, the usual pneumonia pathogens (eg gram-negative bacteria) are still the most common cause of VAP.
Pathogens to consider in patients with immune compromise who have VAP include:
- respiratory viruses that can cause pneumonia and pneumonitis – for example, influenza, parainfluenza, human metapneumovirus, coronavirus (eg SARS-CoV-2) and RSV
- cytomegalovirus (CMV)
- bacterial pathogens
- anaerobes not adequately treated with standard empirical therapy – especially in patients with severe periodontal disease or putrid sputum
- Burkholderia pseudomallei – can cause pneumonia in tropical regions of Australia1, particularly in patients with risk factors (such as diabetes, heavy alcohol consumption [including binge drinking], chronic lung or kidney disease, and immunosuppressive therapy [including chronic corticosteroid use])Smith, 2018
- gram-negative bacteria, including Pseudomonas aeruginosa and Stenotrophomonas maltophilia – especially in patients with haematological malignancy or immunoglobulin deficiencies
- Legionella species
- Nocardia species – usually cause focal lung infections
- mycobacterial pathogens
- Mycobacterium tuberculosis – especially in patients from high-prevalence areas
- nontuberculous mycobacteria
- fungal pathogens
- Aspergillus species – can cause invasive aspergillosis in patients with significant immunosuppression (eg neutropenia after intensive chemotherapy)
- Cryptococcus species – usually cause focal lung infections
- Pneumocystis jirovecii
- Strongyloides stercoralis in patients with past or present epidemiological risk of acquiring S. stercoralis.