Legionella infection

Legionella infection is acquired by inhalation of aerosolized bacteria or, rarely, microaspiration of contaminated drinking water.

Presentation includes respiratory symptoms such as cough (may not be productive) and shortness of breath, fever, chills, and chest pain. Other symptoms include headache, nausea, vomiting, abdominal pain, or diarrhea.

Definitive diagnosis is made with a positive laboratory test.

First-line treatment is with a fluoroquinolone or a newer-generation macrolide.

Complications are the same as those for pneumonia and include respiratory failure, parapneumonic effusion, empyema, lung abscess, and death.

Legionella are gram-negative coccobacilli with at least 20 pathogenic species and 70 serogroups. Legionella reproduce intracellularly, including within macrophages, which paradoxically protect them as they replicate.[1]Cianciotto NP. Pathogenicity of Legionella pneumophila. Int J Med Microbiol. 2001 Nov;291(5):331-43. http://www.ncbi.nlm.nih.gov/pubmed/11727817?tool=bestpractice.com ​ Legionella pneumonia, known as Legionnaires' disease, occurs when the bacteria are inhaled (or rarely aspirated) into the lungs. Nonpneumonic Legionella infection is known as Pontiac fever.