Description

The Diagnostic Automation, Inc Legionella G/M/A ELISA kit is an enzyme-linked immunosorbent assay for the qualitative detection of total antibody (IgG/IgM/IgA) to Legionella pneumophila serogroups 1-6 in human sera. This device is for in vitro diagnostic use.

L. pneumophila was identified as the causative agent for Legionellosis (Legionella pneumonia, or Legionnaire\\\\\\\'s Disease) in 1977 (1). Presently, there are more than 25 species and 33 serogroups in the family Legionellaceae, with at least 18 species associated with pneumonia, accounting for roughly 1-5% of all cases of pneumonia (2). L. pneumophila displays a multitude of morphologies including the bacillus, coccobacillus, and elongated fusiform. Although often difficult to perform, the Gram stain will be Gram-negative.

The DAI Legionella IgG/IgA/IgM ELISA kit is designed to detect antibodies to L. pneumophila in human sera. Wells of plastic microwell strips are sensitized by passive absorption with Legionella antigen. The test procedure involves three incubation steps:
1. Test sera (properly diluted) are incubated in antigen coated microwells. Any antigen specific antibody in the sample will bind to the immobilized antigen. The plate is washed to remove unbound antibody and other serum components.
2. Peroxidase Conjugated goat anti-human IgG/IgA/IgM is added to the wells and the plate is incubated. The Conjugate will react with the antibody immobilized on the solid phase in step 1. The wells are washed to remove unreacted Conjugate.
3. The microwells containing immobilized peroxidase Conjugate are incubated with peroxidase Substrate Solution. Hydrolysis of the Substrate by peroxidase produces a color change. After a period of time the reaction is stopped and the color intensity of the solution is measured photometrically. The color intensity of the solution depends upon the antibody concentration in the original test sample.

The antibody response to L. pneumophila may be both specific and nonspecific, since the patient may have antibodies to similar antigens from other Gram-negative bacteria. Optimum times for specimen collection appear to be within the first week of illness, or as soon as possible after the onset (acute specimen), and at least 3 weeks after the onset (convalescent specimen) (3). By the IFA method, a single result of >1:256 is considered presumptive evidence of legionella infection. Diagnostic titers have been reported to be absent in as many as 25% of patients (4), but the use of multiple Legionella species (5,6) as the antigen source and a polyvalent conjugate directed against IgG, IgM, and IgA (7) maximize the accuracy of serological procedures.