Legionaires Disease - Research Paper Example

The laboratory tests of the patients suffering from legionnaire’s disease reveal liver dysfunction, renal dysfunction and electrolyte imbalance. Chest X-ray shows consolidation of portion of lungs. Ataxia, confusion and memory loss are also common signs of legionnaire’s disease. (Levinson 2008) Legionnaire’s disease is caused by a bacteria Legionella pneumophila. Legionella pneumophila is a gram negative, aerobic bacterium which is primarily a human attacking bacterium. Pontiac fever is also caused by legionella pneumophila in which no pneumonic symptoms are seen.

Legionella pneumophila are found in aquatic bodies. Legionella pneumophila bacteria grows at temperatures between 25 ?C to 45 ?C. Legionella pneumophila takes two to ten days to cause legionnaires disease after attacking a person. Legionella pneumophila can also cause the inflammation of pericardium, haemodialysis fistula and infections of the skin. A Legionella pneumophila bacterium is usually transmitted by inhaling aerosol or drinking water containing legionella pneumophila bacteria. Aerosol is a liquid droplet or solid particle which floats in gaseous medium.

Water is evaporated in the form of small droplets which are unable to be seen by naked eye. If the water contains bacteria legionella pneumophila then the evaporated droplet will also contain the bacteria and if someone inhales the droplets then the person will get infected. When a person inhales the aerosol containing legionella pneumophila, the bacteria move towards the lungs but the cilia prevent their entry to the lungs. Smoking causes the injury to the cilia and makes this possible for the bacteria to enter the lungs.

In patients who smoke it is easier for the bacteria to reach the lungs and attack the respiratory cells. The bacteria enter the cells in response to which the neutrophils and macrophages migrate towards the bacteria to destroy them. The macrophages engulf the bacteria but cannot destroy them and the bacteria start replication within the macrophages. The bacteria replicate in a quantity which makes the macrophage burst and the bacteria come out of the macrophage and attack a new macrophage. Legionella pneumophila does all this with the help of secretions.

The legionella secrete different types of secretions. The chief secretions of legionella pneumophila are type IV secretion system and type II secretion system. Type IV secretion system is called icm (intracellular multiplication) or dot (defective organelle trafficking) which are required for intracellular growth of legionella in macrophages. It is for this reason that legionella pneumophila is also known as intracellular pathogen. Dot/icm secretion is the most important secretion of the legionella pneumophila which is necessary for legionella bacteria pathogenicity.

Dot/icm secretion systems have different substrates like Ralf, LidA, LepA and LepB. The localization of ARF on phagosomes which contain legionella pneumophila requires the Ralf. LidA is required for the multiplication of bacteria within the macrophages; LepA and LepB cause the release of the legionella pneumophila from the macrophages after intracellular multiplication. The sources where the water contains legionella pneumophila bacteria are cooling towers, evaporative coolers, whirlpool spas, ice making machinery