Laboratory methods for the diagnosis of Legionella infections

Abstract

Legionella species have joined the ranks of important human pathogens. Although the number and quality of diagnostic laboratory tests for Legionnaires' disease have increased since the discovery of the etiologic agent, the need for rapid diagnostic procedures and for improved culture techniques is still evident. The diagnostic methods outlined soon after the original description of Legionnaires' disease, such as culture, serology, direct fluorescent antibody testing and urinary antigen detection, still constitute the basic diagnostic repertoire. Significant advancements have been made in diagnostic tests based on the detection of Legionella nucleic acids, especially the polymerase chain reaction. However, none of the diagnostic tests presently available fulfils all the expectations with respect to sensitivity and specificity. Therefore, it is advisable to perform several diagnostic tests in parallel, especially in cases of acute pneumonia in which Legionnaires' disease is suspected. This makes the laboratory diagnosis time consuming and expensive and calls for an assessment of advantages and limitations of each of the methods currently available for diagnosing Legionnaires' disease.