The Bacterial Cause of Legionnaires’ Disease
A member of the genus Legionella, L. pneumophila is a Gram negative aerobic, flagellated, non-spore forming bacteria. It is pathogenic, known to be the cause of Legionnaires’ Disease, a severe, often deadly form of pneumonia.
Common in natural water sources, legionella can be found in indoor environments, even cleanroom and medical environments, where commercial water systems are in use. HVAC systems, cooling towers, condensers, and hot water systems are all at risk.
It is in human made water systems, even shower heads and sink faucets, where Legionella can multiply. (Home and auto air-conditioners do not use water to cool the air, so they do not present a risk for Legionella growth.)
Each year, an estimated 10,000 to 18,000 people in the U.S. become infected with Legionella bacteria. The infection is known as legionellosis and can result in either a mild influenza-like sickness called Pontiac fever, or the more serious condition known as Legionnaires’ Disease, which is potentially lethal form of pneumonia.
Legionella growth by itself is not enough to cause the disease; the bacteria must be spread in water droplets small enough breathe in. Even then, most healthy people exposed to Legionella do not get sick. (You can’t catch legionnaires’ disease from person-to-person contact.)
Those at risk include people with compromised immune systems, those 50 and older, current or former smokers, people with cancer or lung diseases, and those with other underlying illnesses.
Legionnaires’ disease typically develops within 2 to 10 days of exposure and symptoms include a significant fever (104 F or more), cough, chills, and muscle aches. Additional symptoms that develop within a few days are: cough, shortness of breath, chest pain, confusion, and gastrointestinal symptoms like vomiting and diarrhea.
In treatment, legionella bacteria are susceptible to a variety of antibiotics. The two most effective classes of antibiotic are the macrolides (azithromycin), and the quinolones, including ciprofloxacin, levofloxacin, moxifloxacin, gemifloxacin, trovafloxacin.
Additional antibiotics known to be effective against Legionnaires’ disease include tetracycline, doxycycline, minocycline, and trimethoprim/sulfamethoxazole.
Environmental laboratory testing of all commercial water and cooling systems can aid in identifying legionella species and most importantly Legionella pneumophila systems with the potential to aerosolize the bacteria in water droplets small enough to breathe in.
At U.S. Micro Solutions, our microbiology laboratory is a licensed, accredited source for thorough, cutting edge environmental testing, including USP 797, Legionella, indoor environmental testing, healthcare & medical testing, water analysis, and identification of specific pathogens. Visit our Laboratory Services page to learn more.
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