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Pulmonary infection complicating intra-abdominal sepsis: clinical and experimental observations
Abstract:
Pulmonary infection complicating intra-abdominal abscess is a major clinical problem. One hundred and forty-three patients with abdominal abscesses were reviewed; 41 had associated pneumonia by strictly defined criteria. The causative organisms for the pneumonia were Pseudomonas (35), Klebsiella (20), and Enterobacter (16), while abdominal infections were caused by Escherichia coli (22), Klebsiella (21), and Enterococcus (18). The temporal and bacteriologic relationship between the abdominal and pulmonary infection suggested that decreased pulmonary host defenses might be operative in the high incidence of pneumonia observed. An experimental model for intra-abdominal abscess was created using cecal ligation in the rat. Animals with an abdominal abscess had a marked depression of their ability to clear E. coli and Pseudomonas aeruginosa that were injected into the airway. Macrophages from infected animals did not differ in quantity or viability when compared with those in control animals. The ability to ingest bacteria appeared to be normal or enhanced in infected animals, but there was a significant decrease in the ability of the macrophage to kill the ingested organisms. Such macrophage defects may be partially responsible for the infected animals' inability to clear bacteria in a normal manner.
Insights
Intra-abdominal abscesses can lead to pneumonia by weakening lung defenses. Studies show impaired macrophage function in infected animals, hindering bacterial clearance and increasing pneumonia risk.
Area of Science:
- Infectious Diseases
- Pulmonology
- Surgical Pathology
Background:
- Pulmonary infections frequently complicate intra-abdominal abscesses, posing a significant clinical challenge.
- A high incidence of pneumonia was observed in patients with abdominal abscesses.
Purpose of the Study:
- To investigate the relationship between intra-abdominal abscesses and the development of pneumonia.
- To explore the underlying mechanisms of impaired pulmonary host defenses in the context of abdominal infections.
Main Methods:
- Retrospective review of 143 patients with intra-abdominal abscesses to identify associated pneumonia.
- Development of an experimental rat model of intra-abdominal abscess using cecal ligation.
- Assessment of bacterial clearance and macrophage function (quantity, viability, ingestion, and killing capacity) in infected rats.
Main Results:
- Forty-one of 143 patients with abdominal abscesses had associated pneumonia.
- Common pathogens included Pseudomonas, Klebsiella, and Enterobacter for pneumonia, and Escherichia coli, Klebsiella, and Enterococcus for abdominal infections.
- Experimental abscesses in rats led to impaired clearance of airway-introduced bacteria (E. coli, Pseudomonas aeruginosa).
- Macrophages from infected rats showed normal quantity and viability but a decreased ability to kill ingested bacteria.
Conclusions:
- Intra-abdominal abscesses appear to compromise pulmonary host defenses, increasing pneumonia susceptibility.
- Defects in macrophage bactericidal activity may contribute to the reduced ability to clear pulmonary infections in the presence of abdominal abscesses.