LEGIONELLA PNEUMOPHILA

Legionella pneumophila is the etiologic agent of Legionella or Legionnaires’ disease a serious form of pneumonia, clinically indistinguishable from other pulmonary infectious diseases, cause of 2-5% of all community-acquired pneumonia (CAP). From an epidemiological standpoint, L. pneumophila serotype 1 (LPsg1) is responsible for 91% of the cases in the US and of 95% in Europe.Infection occurs by inhalation of aerosol or water contaminated with the bacterium (air conditioning ducts, vaporizers),which may persist for a long time inside the cells.The clinical signs are relevant from the very beginning, with high fever, dry cough, respiratory failure, which can be accompanied by confusional state and hyponatremia.The chest radiograph examination reveals one or more exudative effusions located in different lung areas.The diagnosis is often a conundrum for the clinicians, because of the nonspecificity of the symptoms; however, the frequent seriousness of the clinical picture requires a timely etiological feedback.The bacterial culture from samples of blood, sputum, BAL, pleural effusion, is considered as the microbiological “gold standard”, but the slow response times and an extremely variable sensitivity (10-80%) affect its overall quality. The introduction of tests based on gene amplification, in particular the Real-Time PCR method, represents an innovative diagnostic device, however, the preparation of analytical sessions is related to the number of samples and is also linked to the quality and type of the examined sample.In the current practice it has spread more and more the use of tests for the detection of specific LPsg1 antigen in urine samples, so to have effectively replaced the bacterial culture, since soluble antigen fragments appear very early (one day after onset of symptoms) and persist for days and weeks. The sensitivity amounts to 70-100%, while the specificity is nearly 100%. A simple complementary approach is represented by the search for anti-L. pneumophila sg1 class IgG and IgM antibodies with ELISA method. Although conditioned by the delayed immunological reaction to the germ, the serological diagnosis enriches the diagnostic potentialities and solves the crux of the rapidity of response to the clinical question.DIESSE Diagnostica Senese SpA provides the clinical laboratory with immunoassay kits for direct research of Urinary Antigen and for the detection of anti-Legionella IgG and IgM, for a complete and accurate diagnosis of legionellosis, in the Chorus convenient and functional ready-to-use single test format.

Method:

Immunoenzymatic method for the qualitative determination of IgG and IgM-class antibodies to legionella pneumophila in human serum, using a disposable device applied on the Chorus and Chorus TRIO instruments.The test is based on the ELISA principle (Enzyme Linked ImmunoSorbent Assay) which uses the reaction between the antibodies present in the tested sample and the immobilized antigen bound to solid phases.The immunoglobulins bind to the antigen through incubation with diluted human serum.The disposable devices contain all the reagents to perform the test when applied on the Chorus instruments. The results is expressed as an INDEX (ratio between the OD value of the sample and that of the Cut-off).