First recognized in 1978 after the 1976 Philadelphia cooling tower outbreak, Legionnaires’ disease is a severe form of pneumonia caused by the bacterium Legionella pneumophila and other Legionella species. Legionella naturally live in water biofilms and are most commonly found in water systems containing warm water such as hot tubs, cooling towers, and hot water tanks. This bacterium is considered a biohazard by the CDC and an estimated 10,000 – 18,000 become infected each year in the US.
Legionnaires’ disease can be hard to diagnose, because its symptoms are nearly identical to other pneumonias, including a high fever, chills, muscle aches, headaches, etc. The diagnosis is often missed because Legionella do not grow on standard microbiology agar media, BCYE agar is used. Legionella on BCYE agar media are often overgrown or inhibited by competing microbial flora that mask the presence of legionella colonies, particularly with water samples taken from warm water-containing mechanical equipment exposed to the environment such as fountains, cooling towers, and saunas. Culture on BCYE agar with or without supplements, antimicrobial agents, water sample heat or acid treatment lacks the sensitivity of our quantitative DFA test, which is a monoclonal antibody modification of the original CDC legionella test. Patients admitted to the hospital are usually diagnosed by a urine antigen test specific for Legionella pneumophila serogroup 1. Below are 6 basic, yet essential facts about legionella that we feel you should know.
1. There are two different illnesses caused by legionella bacteria: Legionnaires’ disease, the lethal pneumonia, and Pontiac fever, a milder influenza-like illness.
2. Legionella bacteria in water systems are be difficult to detect, especially with culture methods. These water systems can produce Legionella-containing aerosols that are inhaled and cause a serious pneumonia.
3. Though hospitalization is required to treat Legionnaires’ disease, also called legionellosis, it is treatable with antibiotics if the pneumonia is promptly diagnosed.
4. There are some complications caused by legionellosis, mainly respiratory failure, septic shock and acute kidney failure. Early antibiotic treatment is the best line of defense to prevent these complications.
5. Legionnaires’ disease does not spread from person to person (only one exception to this is in the published literature). It is contracted by breathing in contaminated aerosol or small droplets.
6. The most effective way to prevent legionella from multiplying in water systems is proper maintenance, whether it’s your home’s hot water tank or corporate cooling tower. Legionella water testing is performed to determine whether your maintenance program is working properly.