Diseases Caused by Pseudomonas aeruginosa
Pseudomonas aeruginosa primarily causes respiratory tract infections in specific high-risk populations, with cystic fibrosis lung disease, hospital-acquired pneumonia, and ventilator-associated pneumonia being the most clinically significant manifestations, while it rarely causes disease in healthy individuals.
Respiratory Tract Infections
Cystic Fibrosis (CF)
- P. aeruginosa is the most frequent pathogen isolated from CF patients across all age groups, representing the greatest cause of morbidity and mortality in this population, leading to premature death in 90% of CF patients. 1
- The infection prevalence increases dramatically with age: 29.8% of children aged 2-5 years and 81.3% of adults aged 26-30 years are infected with P. aeruginosa. 1, 2
- Chronic P. aeruginosa infection in CF causes progressive lung tissue damage due to chronic inflammation and biofilm formation. 1
- P. aeruginosa is rarely and only transiently isolated from healthy humans, making its presence in CF patients pathologically significant rather than colonization. 1, 2
Hospital-Acquired and Ventilator-Associated Pneumonia (HAP/VAP)
- P. aeruginosa is the most common multidrug-resistant gram-negative pathogen causing HAP/VAP, particularly in ICU patients. 1
- The organism comprised 50% of respiratory tract isolates from patients with nosocomial pneumonia in surveillance studies. 2
- P. aeruginosa causes high morbidity and mortality in ventilator-associated pneumonia, with infections difficult to eradicate due to intrinsic antibiotic resistance mechanisms. 3, 4
Community-Acquired Pneumonia (CAP)
- P. aeruginosa is found in approximately 4% of all CAP patients with an established etiologic diagnosis, though this represents a relatively uncommon cause in the general population. 1
- The incidence rises significantly (10-15% of cases) in ICU-admitted CAP patients, particularly those with underlying bronchiectasis or structural lung disease. 1
- Risk factors requiring Pseudomonas coverage include: structural lung disease (bronchiectasis, COPD), corticosteroid therapy (≥10 mg prednisone daily), broad-spectrum antibiotic therapy for ≥7 days in the past month, and malnutrition. 1, 2
Aspiration Pneumonia
- P. aeruginosa should be considered in aspiration pneumonia patients with structural lung disease, prior antibiotics, or prolonged hospitalization. 5
- In nursing home residents with aspiration, Pseudomonas species accounted for 4% of initial isolates but 14% in those who failed initial antibiotic therapy. 5
Urinary Tract Infections
- P. aeruginosa causes UTIs particularly in patients with indwelling urinary catheters, where it forms biofilms that are difficult to eradicate with antibiotics alone. 6
- Catheter removal or replacement is necessary as antibiotic therapy alone is insufficient to clear biofilm-associated infections. 6
Burn Wound Infections
- P. aeruginosa causes severe infections in severely burned patients, representing a major cause of morbidity and mortality in this population. 1, 3
Other Infections in Immunocompromised Hosts
- P. aeruginosa causes infections in cancer patients, paraplegic patients, and those with immunodeficiency. 1, 4, 7
- The organism infects patients with chronic obstructive pulmonary disorder (COPD) and those requiring mechanical ventilation for severe infections including COVID-19. 7
- Surgical wound infections occur in hospitalized and immunocompromised patients. 3, 8
Key Clinical Distinctions
- P. aeruginosa is seldom isolated from healthy humans, and when present, represents transient colonization rather than infection. 1, 2
- The organism is ubiquitous in water reservoirs and hospital environments, with transmission occurring through direct patient-to-patient contact or contaminated environmental reservoirs. 1
- Infections are characterized by difficulty in eradication due to multiple antibiotic resistance mechanisms, biofilm formation, and numerous virulence factors. 4, 7, 8