Legionella

Legionella

Legionella is a type of bacteria that can be found in places like soil and water. These tiny living things can make people sick, causing illnesses such as Legionnaires' disease, which is like pneumonia, and Pontiac fever, which feels like the flu. Although Legionella is common, it does not spread from one person to another. Most people who come into contact with these bacteria do not get sick. However, outbreaks of illness sometimes happen when cooling towers, which are used to cool buildings, are not kept clean and maintained properly.

Legionella bacteria are special because they live inside tiny organisms called amoebae. Scientists can see these bacteria using certain stains or grow them in special laboratory conditions that include an amino acid called cysteine. There are over fifty different kinds of Legionella, each with its own characteristics. The outer layer, or cell wall, of these bacteria helps scientists classify them into different types based on its structure and the sugars it contains.

Etymology

The name Legionella comes from an illness that appeared in 1976. This happened during a meeting of the American Legion, a group of U.S. military veterans, in Philadelphia. Many people got very sick at this event, and doctors didn’t know what was causing it at first. Later, they found that a new type of bacteria was responsible, and they named it Legionella after the group where it was first found.

Detection

Detecting Legionella bacteria needs special food called buffered charcoal yeast extract agar that has cysteine and iron. Normal lab food doesn’t work because Legionella needs these special ingredients to grow.

To find Legionella in water, scientists gather the water tightly together, then put a tiny bit onto the special agar. Sometimes they use heat or acid to clear away other tiny living things in the sample.

After waiting up to ten days, if Legionella is there, it will grow on the special agar but not on normal agar. Then, they use special tests to figure out which kind of Legionella is present.

Some hospitals use a quick test with urine when they think someone might have a lung infection from Legionella. This test is fast and finds only one common kind of Legionella, but other kinds need the special growing method to be found.

There are also faster ways to detect Legionella in water, like using polymerase chain reaction (PCR) and rapid immunological tests.