Under a low magnification of 5X, this photograph depicted a number of Legionella pneumophila colonies that had been cultivated on Feeley-Gorman (FG) agar. Note the “cut-glass” appearance displayed by the round, off-white colored colonies. FG agar is used particularly in the cultivation of Legionella spp. bacteria, and is composed of casein (acid hydrolyzed), agar, beef extract, starch, cysteine and iron (III) pyrophosphate (Fe4(P2O7)3).
How do people get Legionnaires’ disease?
People get Legionnaires' disease when they breathe in a mist or vapor (small droplets of water in the air) that has been contaminated with the bacteria. One example might be from breathing in the steam from a whirlpool spa that has not been properly cleaned and disinfected.
The bacteria are NOT spread from one person to another person.
Outbreaks are when two or more people become ill in the same place at about the same time, such as patients in hospitals. Hospital buildings have complex water systems, and many people in hospitals already have illnesses that increase their risk for Legionella infection.
Other outbreaks have been linked to aerosol sources in the community, or with cruise ships and hotels, with the most likely sources being whirlpool spas, cooling towers (air-conditioning units from large buildings), and water used for drinking and bathing.
Credit: Dr. Jim Feeley, CDC