Ligionella

ligionella

legionella pneumophila Legionella pneumophila is a thin, aerobic, pleomorphic, flagellated, non-spore forming, Gram-negative bacterium of the genus Legionella. L. pneumophila is the primary human pathogenic bacterium in this group and is the causative agent of legionellosis or Legionnaires' disease

Legionella may be readily visualized with a silver stain or cultured in cysteine-containing media such as BCYE. It is common in many environments, including soil and aquatic systems, with at least 50 species and 70 serogroups identified. The bacterium, however, is not transmissible from person to person:[3] furthermore, most people exposed to the bacteria do not become ill

Dignosis

Legionella is traditionally detected by culture on buffered charcoal yeast extract (BCYE) agar. Legionella requires the presence of cysteine and iron to grow, so does not grow on common blood agar media used for laboratory-based total viable counts or on-site dipslides. Common laboratory procedures for the detection of Legionella in water[6] concentrate the bacteria (by centrifugation and/or filtration through 0.2-μm filters) before inoculation onto a charcoal yeast extract agar containing antibiotics (e.g. glycine, vancomycin, polymixin, cyclohexamide, GVPC) to suppress other flora in the sample. Heat or acid treatment are also used to reduce interference from other microbes in the sample

Many hospitals use the Legionella urinary antigen test for initial detection when Legionella pneumonia is suspected. Some of the advantages offered by this test are that the results can be obtained in a matter of hours rather than the five days required for culture, and that a urine specimen is generally more easily obtained than a sputum specimen. Disadvantages are that the urine antigen test only detects antigen of Legionella pneumophila serogroup 1 (LP1); only a culture will detect infection by non-LP1 strains or other Legionella species and that isolates of Legionella are not obtained, which impairs public health investigations of outbreaks of LD.[8]
New techniques for the rapid detection of Legionella in water samples are emerging, including the use of polymerase chain reaction and rapid immunological assays (direct flouresent antibody test ). These technologies can typically provide much faster results samples are










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NOTE : IFA (indirect flourescent antibody)