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Abstract:
During a six-month period, we observed an increase in the incidence of presumed Legionnaires' disease (LD) due to false-positive direct immunofluorescent antibody (DFA) staining. Contamination of the DFA staining reagents with Legionella appeared to account for our pseudoepidemic. Although a positive DFA stain has been regarded as highly specific for the diagnosis of LD, the clinician must interpret such results with caution.
Insights
A six-month study revealed increased Legionnaires
Area of Science:
- Clinical microbiology
- Infectious disease diagnostics
- Immunofluorescence assays
Background:
- Legionnaires' disease (LD) is a severe pneumonia.
- Direct immunofluorescent antibody (DFA) staining is a diagnostic tool for LD.
- Accurate diagnosis is crucial for patient management and public health.
Purpose of the Study:
- To investigate a pseudoepidemic of Legionnaires' disease.
- To identify the cause of increased presumed LD cases.
- To evaluate the reliability of DFA staining in diagnosing LD.
Main Methods:
- Retrospective analysis of presumed LD cases over six months.
- Investigation of DFA staining procedures and reagents.
- Microbiological testing of staining reagents for Legionella contamination.
Main Results:
- An increase in presumed Legionnaires' disease diagnoses was observed.
- False-positive DFA staining results were identified as the cause.
- Contamination of DFA staining reagents with Legionella bacteria was confirmed.
Conclusions:
- Direct immunofluorescent antibody staining reagents can become contaminated with Legionella.
- Contaminated reagents can lead to pseudoepidemics of Legionnaires' disease.
- Clinicians should interpret positive DFA results cautiously, considering potential reagent contamination.