Legionella

Definition

Legionella is a genus of pathogenic Gram-negative bacteria that includes the species L. pneumophila, responsible for causing Legionnaires' disease. These bacteria thrive in aquatic environments and can infect humans through inhalation of contaminated water droplets.

5 Must Know Facts For Your Next Test

1. Legionella are Gram-negative, rod-shaped bacteria.
2. The most clinically significant species is Legionella pneumophila, which causes Legionnaires' disease.
3. Legionella bacteria are commonly found in freshwater environments but can proliferate in man-made water systems like cooling towers and hot tubs.
4. Infection typically occurs through inhalation of aerosolized water containing the bacteria, not through person-to-person transmission.
5. They require special culture conditions for laboratory growth, often using buffered charcoal yeast extract (BCYE) agar.

Review Questions

• What type of environment does Legionella thrive in?
• Which species of Legionella is primarily responsible for human illness?
• How do humans typically become infected with Legionella?

Related terms

Gram-negative bacteria: Bacteria that do not retain the crystal violet stain used in the Gram staining method.

Legionnaires' disease: A severe form of pneumonia caused by inhaling aerosolized water contaminated with Legionella pneumophila.

Buffered Charcoal Yeast Extract (BCYE) agar: A specialized growth medium used to culture and isolate Legionella species.