The Legionella organism is a Gram negative, rod shaped bacterium that can cause pneumonia (Legionnaires’ disease) or a flu-like illness (Pontiac fever). Legionella test is used to detect and diagnose legionella bacteria as the cause of pneumonia.
Negative legionella test results may indicate that infection of a Legionella species other than the one(s) tested or the bacteria may be present in the sample in numbers too low to be detected or may not have grown in culture.
Positive legionella test results may indicate Legionella pneumophila serogroup 1 infection. Usually, positive legionella culture is a sign of having a legionella infection.
Results of testing must be carefully interpreted and evaluated in conjunction with a complete medical history, physical exam, and other tests such as a chest X-ray for pneumonia.