Microbes In The News: Legionnaire’s Disease

Legionella_pneumophila_(SEM)This year, a total of six veterans who were at the Veteran’s Administration hospital in Pittsburg were diagnosed with Legionnaire’s disease. Now, the Legionella pneumophila bacteria that causes Legionnaire’s disease has been found on three water fixtures in the same hospital. The first three cases that occurred earlier this year were not the same strain as those found on the hospital water fixtures, while the three cases that occurred in September are still being tested to determine their strain.

Legionnaire’s disease is a severe to lethal type of pneumonia caused by Legionella pneumophila. The bacteria is naturally found in bodies of water such as rivers, lakes, and streams. The bacteria can be found in both potable and non-potable water.  Legionella pneumophila can cause disease when it is found in water distribution systems, mist machines, humidifiers, and spas.

Legionella pneumophila is a Gram negative bacteria.  This bacteria uses macrophages as hosts – when the bacteria undergoes phagocytosis, the bacteria starts to replicate in the macrophage. The bacteria prevents the macrophage from delivering it to the lysosome.  The bacteria also has a thick cell membrane that prevents it from being digested.  Once the bacteria replicates, it depletes the macrophage of nutrients, lyses the host macrophage and continues infecting other macrophages.

The infection of Legionella pneumophila causes pneumonia.  The effected population are: people 50 years old and over, people who have or currently smoke, individuals who have a chronic lung disease such as emphysema or COPD (chronic obstructive pulmonary disease), individuals who have a weak immune system or are taking drugs that weaken the immune system.  Symptoms include a fever over 103°F, diarrhea, nausea, vomiting, and a cough that has mucous. Legionnaire’s disease can be treated by antibiotics.

The CDC estimates between 8,000 to 18,000 people are hospitalized in the U.S. every year. Lately, there seem to be quite a few news stories regarding this bacteria. Recent outbreaks have occurred at the San Quentin State Prison in California, an Illinois Veteran’s home, and Legionella pneumophila has been found in cooling towers in New York. Legionnaire’s disease is of particular concern to people who are at risk or have family members who are at risk.  Additionally, there is not much a person can do to prevent exposure to the bacteria.  The ordinary person blindly trusts businesses, hospitals, and other care facilities to maintain their water distribution systems.


VA Pittsburgh finds Legionella bacteria on 3 water fixtures

Legionella – About the Disease

Legionella Pneumophila Life Cycle and Identifying Character

Legionella (Legionnaires’ Disease and Pontiac Fever)