Chest
Volume 101, Issue 4, April 1992, Pages 1005-1012
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Clinical Investigations
Microbial Etiology of Acute Pneumonia in Hospitalized Patients

https://doi.org/10.1378/chest.101.4.1005Get rights and content

The purpose of this study was to determine the microbial etiology of pneumonia by using strict criteria among a group of hospitalized patients. Patients with acute community-acquired or hospital-acquired pneumonia were studied in a systematic and comprehensive manner for bacterial, viral, chlamydial, mycobacterial, and fungal pathogens. A total of 198 patients with 204 episodes of pneumonia were evaluated. Despite 100 percent follow-up of all surviving patients, a specific etiologic agent could be found in only 103 episodes. Among 154 episodes of community-acquired pneumonia, a diagnosis was made in 79; the most common pathogen was from the genus Legionella, followed by various Gram-negative enteric bacteria, Gram-positive cocci, influenza A virus, and Mycoplasma pneumoniae. The etiologic agent was found in 24 of the 50 patients with hospital-acquired pneumonia; no pathogen predominated. We conclude that even when elaborate diagnostic studies are done, including many invasive procedures, the etiology can be determined in only about half of the patients with acute pneumonia. The pathogens of pneumonia in this study are not markedly different between community-acquired and hospital-acquired infection.

Section snippets

Patient Selection

All patients hospitalized on the medical service of the John L. McClellan Veterans Administration Medical Center, Little Rock, Ark, during the calendar year 1985 (approximately 6,500 admissions) were evaluated both on admission and throughout their hospital course for the presence or development of pneumonia. All patients with clinical evidence of pneumonia were evaluated within 24 h for inclusion in the study. For selection, each patient was required to have a new or progressive pulmonary

Patients

In all, 233 patients who experienced a total of 240 episodes of suspected pneumonia were evaluated and admitted to the study. Each met the criteria established for entry, but on retrospective review after days or weeks of follow-up, 36 episodes involving 35 patients were diagnosed as due to another disease, such as pulmonary edema, pulmonary infarction, atelectasis, or tumor. Thus, for final analysis 198 patients with 204 episodes of pneumonia were studied and followed up to recovery or death.

DISCUSSION

It is distressing that, despite extensive laboratory testing and many invasive procedures done to obtain material for study, we were able to establish the pathogen in only 50 percent of the patients studied. However, our results are not substantially lower than those in other studies, in which an etiologic agent was found in only 67 percent, 55 percent, and 49 percent of patients.11, 12, 13, 14 There are several reasons why we found fewer pathogens than expected. Wishing to use very strict

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    Supported in part by a grant from Abbott Laboratories, Abbott Park, Ill.

    Manuscript received May 28; revision accepted July 24.

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