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Extrinsic risk factors for pneumonia in the patient at high risk of infection
Abstract:
Most nosocomial pathogens cause pneumonia through the following sequence: transit to the patient on the hands of medical personnel or perhaps in food, proliferation in the nasopharynx, and subsequent pulmonary aspiration. There are three exceptional pathogens, each of particular concern as a cause of pneumonia in the immunocompromised patient, which follow atypical routes. Important recent advances in understanding these routes permit more rational preventive measures. This report examines the evidentiary basis for the following pathophysiolgic propositions about these three pathogens: Aspergillus, Pneumocystis carinii, and Legionella. Aspergillus spores are almost ubiquitous. Spore generation, except in very unusual circumstances, takes place outside the hospital. Most spores enter the hospital borne in air by infiltration or because of incomplete filtration. Air filtration systems of moderate efficiency remove Aspergillus spores. Nosocomial pulmonary and disseminated aspergillosis arises from inhalation of airborne spores. A nasopharygeal colonization intermediate step before pulmonary disease has not yet been solidly established. It is now firmly established that airborne Pneumocystic carinii transmission occurs between animals. Airborne acquisition probably occurs early in human life. However, in-hospital, person-to-person transmission has yet to be convincingly demonstrated. Most or all cases of pneumocystosis in adults are due to reactivation of endogenous pulmonary organisms. Intensive diagnostic efforts reveal that Legionella is a common cause of community-acquired and nosocomial pneumonia in hospitals where it had not previously been recognized. However, there are at least a few hospitals where it is an uncommon source of pneumonia. Several hospitals have demonstrated a temporal association between the presence of Legionella in hot water systems and nosocomial cases of Legionella pneumonia. The mechanism or mechanisms of transmission to the patient remain to be delineated. It is also not determined if all hospital hot water systems should be maintained Legionella free.
Insights
This study examines atypical pneumonia-causing pathogens: Aspergillus, Pneumocystis carinii, and Legionella. Understanding their unique transmission routes is key to developing effective preventive strategies for immunocompromised patients.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Hospital Epidemiology
Background:
- Most nosocomial pneumonia pathogens spread via direct contact or nasopharyngeal colonization.
- Three pathogens—Aspergillus, Pneumocystis carinii, and Legionella—cause pneumonia through atypical routes, particularly in immunocompromised patients.
Purpose of the Study:
- To review the pathophysiological basis of pneumonia caused by Aspergillus, Pneumocystis carinii, and Legionella.
- To explore recent advances in understanding the transmission routes of these exceptional pathogens.
- To inform the development of rational preventive measures against these nosocomial pathogens.
Main Methods:
- Review of existing literature and evidentiary basis for pathophysiological propositions.
- Analysis of transmission routes for Aspergillus, Pneumocystis carinii, and Legionella.
- Examination of epidemiological data linking environmental factors to nosocomial pneumonia.
Main Results:
- Aspergillus pneumonia arises from inhaling airborne spores, with hospital air filtration being a key control point.
- Pneumocystis carinii pneumonia is likely due to reactivation of endogenous organisms in adults, with airborne transmission established between animals but not convincingly between humans in hospitals.
- Legionella is a significant cause of both community-acquired and nosocomial pneumonia, often associated with hospital hot water systems, though transmission mechanisms require further elucidation.
Conclusions:
- Understanding atypical pathogen transmission is crucial for preventing nosocomial pneumonia in vulnerable populations.
- Airborne precautions for Aspergillus and recognizing Legionella in water systems are important.
- Further research is needed to clarify Pneumocystis carinii and Legionella transmission dynamics and optimal control strategies.