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Legionnaires' disease: structural characteristics of the organism
Abstract:
The Legionnaires' disease organism was isolated from lung tissue taken from two fatalities of the Legionnaires' disease epidemic that occurred in Philadelphia during 1976. In yolk sac tissue the agent grew as a small coccobacillary microorgansim, which was Gram variable and Giménez positive. Intracellular coccoid and bacillary forms, detected by electron microscopy, within and without vacuoles, underwent multiplication by septate binary fission. Some of the intracellular forms resembled obligate intracellular pathogens. On defined bacteriologic media, the organisms were predominantly bacillary. The organism conforms to the morphologic criteria of a prokaryocyte.
Insights
Researchers identified the Legionnaires' disease bacterium from fatal cases during the 1976 Philadelphia epidemic. This prokaryotic organism exhibited varied morphology and multiplication within host cells, confirming its pathogenic nature.
Area of Science:
- Microbiology
- Pathogen Discovery
- Epidemiology
Background:
- The 1976 Philadelphia Legionnaires' disease outbreak prompted an urgent search for the causative agent.
- Understanding the pathogen's morphology and behavior is crucial for diagnosis and treatment.
Purpose of the Study:
- To isolate and characterize the Legionnaires' disease organism from human fatalities.
- To determine the microorganism's morphology, growth patterns, and cellular characteristics.
Main Methods:
- Isolation of the organism from lung tissue of deceased patients.
- Cultivation in yolk sac tissue and defined bacteriologic media.
- Microscopic examination (Gram staining, Giménez staining, electron microscopy) to analyze morphology and intracellular behavior.
Main Results:
- The Legionnaires' disease bacterium was successfully isolated from lung tissue.
- The organism presented as small, Gram-variable, Giménez-positive coccobacillary forms in yolk sac tissue.
- Electron microscopy revealed intracellular and extracellular coccoid and bacillary forms multiplying via binary fission.
- The bacterium exhibited characteristics consistent with obligate intracellular pathogens and prokaryotes.
Conclusions:
- The isolated organism meets the morphological criteria of a prokaryote.
- The findings confirm the identification of the Legionnaires' disease bacterium and elucidate its basic biological characteristics.