Specimen Information

Type

Respiratory tract specimens (secretions, aspirates, BAL, tissue, fluids, sputum, abscess material) or pericardial fluid

Volume

Prepared slides: 2
Fluids: 1.0 mL

Transport Info

Refrigerate 48 Hours or Frozen

Fasting Required?

False

Clinical Significance

Diagnosis of Legionnaires' disease or Pontiac fever.

Two syndromes are caused by legionellae: Legionnaires' disease, an acute lobar pneumonia with multisystem manifestations. Pontiac fever, a nonpneumonic, influenza-like illness. Legionnaires' disease results from exposures to aerosols generated from water sources containing the organism, is more common in men than women, and is more prevalent during the summer months. Predisposing factors in a susceptible host include a compromised immune system (immunosuppressive therapy or T- cell dysfunction), underlying disease, recent surgery, increased age, and heavy smoking. Pontiac fever is a self-limiting, febrile illness usually affecting healthy individuals. Of the 40 known species of Legionella, L. pneumophila is the major pathogen, and is the most commonly encountered member of the group in the clinical laboratory. The organisms are nutritionally fastidious, nonsporeforming, aerobic, gram-negative, slender rods. Media containing cysteine, yeast extract, a-ketoglutarate, and iron (BCYE) are required for isolation of Legionella from clinical material. A second medium, selective BCYE (or other medium-containing antibiotics), is recommended for sputums and other specimens likely to be contaminated with normal flora. Colonies gray-white to blue-green typically grow 5 days after incubation at 37şC. L. pneumophila can be identified by a monoclonal immunofluorescent stain. Direct immunofluorescence (DFA) is used for the rapid diagnosis of Legionnaires' disease. Appropriate specimens are stained with anti-Legionella pneumophila staining reagent, which contains a single monoclonal antibody that is labeled with fluorescein isothiocyanate. This antibody reacts with a protein present in the outer membrane of all known serogroups of L. pneumophila. The overall sensitivity is reported to vary from 25 to 70%. Specificity is 99%.