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Published on: June 19, 2012
Isolation of Legionella pneumophila from clinical specimens: salutary effects of lung tissue dilution
Abstract:
Diagnosis of legionnaires' disease is seldom confirmed by isolation of Legionella pneumophila. In 2 cases, isolates were obtained using inoculums of diluted lung tissue suspension, even though no growth ocurred when undiluted suspensions were used. It is speculated that tissue dilution decreases the concentration of antimicrobial agents and antibacterial properties associated with lung host defense mechanisms, which allows improved recovery rates. This technique is recommended when attempting isolation of L. pneumophila from clinical specimens.
Insights
Diagnosing legionnaires' disease can be improved by diluting lung tissue samples before culturing Legionella pneumophila. This method enhances bacterial recovery by reducing inhibitory factors in undiluted samples.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Respiratory Medicine
Background:
- Legionnaires' disease diagnosis is often challenging.
- Isolation of Legionella pneumophila from clinical samples is infrequently successful.
Purpose of the Study:
- To investigate a method for improving the isolation rate of Legionella pneumophila from lung tissue.
- To evaluate the efficacy of using diluted lung tissue suspensions for bacterial culture.
Main Methods:
- Two cases of suspected Legionnaires' disease were analyzed.
- Lung tissue samples were prepared as both undiluted and serially diluted suspensions.
- Cultures were performed using both types of inoculums to assess bacterial growth.
Main Results:
- Legionella pneumophila was isolated from lung tissue only when using diluted suspensions.
- No growth was observed when undiluted lung tissue suspensions were used for inoculation.
- Dilution of lung tissue appears to overcome inhibitory factors present in the original sample.
Conclusions:
- Diluting lung tissue suspensions is a valuable technique for enhancing the recovery of Legionella pneumophila.
- This method may improve the diagnostic yield of Legionnaires' disease when direct culture is attempted.
- Reduced antimicrobial agents and host defense factors in diluted samples likely facilitate bacterial growth.
