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Transcript
By Louis Martin The organism behind the disease: •Legionnaire’s disease, or Legionellosis , is a very severe type of pneumonia. •It is caused by the bacterium known as Legionella pneumophila. •As you can see from the images to the right, L. pneumophila is a rod bacterium which may or may not have flagellum. •The bacterium is also gram negative, a quality which is characteristic of pathogenic organisms. The cells do not stain due to the lipopolysaccharides in the cellular membrane. •The lipopolysaccharides do many things for the bacterium, most importantly they present antigens which, when combined with gram negative bacteria, can be modified so that the immune system initially does not see the pathogens as a threat, therefore does not attempt to destroy the infection. •The lipopolysaccharides also help to strengthen the cell membranes, providing greater cellular integrity. L. pneumophila •The first diagnosed case of legionnaire’s disease was in 1976 when many people who had been attending a legions convention in America were struck down with pneumonia, it was found that they had an unrecognised bacterial infection, this bacteria was named Legionella pneumophila. •In time it was discovered that the bacteria had came from the contaminated water cooling system used in the air conditioning of the hotel. •The bacteria lives in stagnant water, in this case the cooling system of the air conditioning. It reached the people as it became air born inside the air conditioning unit and was pumped around the hotel until it was inhaled by the attendees of the convention. •Its capability to modify its antigens, allowed it to enter its hosts and overcome their immune systems, the bacteria's optimum conditions are moist areas with a temperature in the region of 35-45 degrees Celsius, so naturally they will grow rapidly once inside a human body. •Since the identification of the bacterium, many have been found particularly in man made water devices such as showers, Jacuzzis, water fountains and room-air humidifiers, basically in any water using devices. •In nature it has been found that the bacteria can live in warm stagnant water quite happily and certain strains of the bacteria can even grow in soil. •The disease is spread by the inhalation of water mist from contaminated water. •The bacteria can be grown in a lab by cultivating lung tissue with the bacteria and keeping it at an optimum temperature of approximately 37 degrees Celsius. •The bacteria can be identified using its unique antigens or comparing the genome of the bacteria with other bacteria for possible matches and also by using direct fluorescent antibody staining on an infected tissue such as lung tissue. Disease process: Symptoms of the Disease: •High fever •Chills •Muscle ache •Cough which will likely eventually produce bloody sputum •Fatigue •Loss of appetite •Pneumonia 1--------------- Days-------------10 •Head aches 1. L.Pneumophila enters the body 2. The bacteria are inhaled into the lungs 3. The bacteria are attacked and engulfed by the bodies phagocytes via phagocytosis 4. Due to its special structure the phagocytes are unable to digest the swallowed bacteria so the bacteria continue to live and they replicate 5. After many replications the phagocyte dies and bursts releasing many more L.pneumophila into the lungs thus strengthening the infection. 6. This continues for 1-10 days as the disease becomes more severe causing the pneumonia •The most common way to treat the disease is with drugs, there are many different types but the two main categories are quinolones and the more modern macrolides. •The most popular of each group being levofloxacin and azithromycin respectively. •These tend to be the most effective as they can enter cells with relative ease and attack the L. pneumophila inside the cells, where as other antibiotics such as penicillin are poor at entering cells. •The macrolides can be used on any age group but the quinolones can only be used on people who are 18 or over. •At this current moment in time there is nothing more effective than these drugs in the fight against legionnaire’s disease, however the genome of L. pneumophila has been completely mapped and scientists believe that soon they will be able to use its genetic coding to create an effective vaccine. As of yet there is no vaccination for legionnaire’s disease, however there are steps which can be taken which will radically reduce the chances of bacterial growth and infection. The bacteria can grow naturally in the wild but most cases of human infection tend to show the source of the bacteria being industrial equipment where the water is contaminated, many cases tend to be water cooling towers. The main ways of prevention and control is just to ensure that any equipment, which may be in contact with stagnant water regularly, is cleaned thoroughly and regularly. The cleaning process involves chemical disinfectant cleaning with chlorine containing compounds, and also mechanical cleaning to ensure all bacteria containing grime and gunk is removed from the surfaces which come in contact with the water. For full cleaning procedures see: http://www.cdc.gov/ncidod/dhqp/pdf/guidelines/Enviro_guide_03.pdf (pages 239-240) http://www.niehs.nih.gov/external/faq/legion.htm http://www.cdc.gov/ncidod/dbmd/diseaseinfo/legionellosis_g.htm http://www.osha.gov/dts/osta/otm/legionnaires/disease_rec.html#Causative pages 802/807 in brock microbiology book. http://en.wikipedia.org/wiki/Legionella_pneumophila http://news.bbc.co.uk/1/shared/spl/hi/health/03/travel_health/diseases/html/legionnaires.stm http://en.wikipedia.org/wiki/Legionellosis#Diagnosis_and_treatment http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_7.html#2-control and prevention http://news.bbc.co.uk/2/hi/science/nature/3677756.stm http://www.cdc.gov/ncidod/dhqp/pdf/gui http://www.google.co.uk/imghp?hl=en&tab=wi&q=