2. A 73-year-old man was admitted to the hospital because of breathing difficult
ID: 193410 • Letter: 2
Question
2. A 73-year-old man was admitted to the hospital because of breathing difficulties, chest pain, chills, and fever of several days' duration. He had been well until 1 week before admission, when he noted the onset of a persistent headache and a productive cough. The patient smoked two packs of cigarettes a day for more than 50 years and drank a six-pack of beer daily; he also had a history of bronchitis. Physical examination revealed an elderly man in severe respiratory distress with a temperature of 39°C, pulse of 120 beats/minutes, respiratory rate of 36 breaths/minutes, and blood pressure of 145/95 mm Hg. Chest radiograph revealed an infiltrate in the middle and lower lobes of the right lung. The white blood cell count was 14,000 cells/mm3 (80% polymorphonuclear neutrophils). Gram stain of the sputum showed neutrophils but no bacteria, and routine bacterial cultures of sputum and blood were negative for organisms. Infection with Legionella pneumophila was suspected. (5pts) What laboratory tests can be used to confirm this diagnosis? Why were the routine culture and Gram-stained specimen negative for Legionella organisms? What environmental factors are implicated in the spread of Legionella infections? How can this risk be eliminated or minimized? a. b. c.Explanation / Answer
a. Legionella pneumophilla causes a fatal pneumonia called as legionares disease. The disease can be diagnosed by various laboratory tests. A few important ones are :1. Culture test on special legionares medium. This is a special medium which provides all essential nutrients for the growth of the bacterium. Through this test all species of Legionella can be identified.
2: Direct fluorescent antibody (DFA) :in this test Legionella is identified by the fluorescent antibodies under fluorescent microscope.
3. Urinary antigen test. In this test urine is tested for the presence of antigen of L pneumophilla.
b. Since Legionella pneumophilla is a gram negative bacteria and has special lipopolysaccharides in its cell Wall ;it does not stain with gram stain. Secondly, it does not grow in iron and cysteine deficient media (routine media) because these are very important for its growth and division.
C. Legionella is an aquatic bacteria and spreads mainly through contaminated water (portable or non portable). Other factors that also help in its dessemination include cooling towers, humidifiers, respiratory Therapy equipment, evaporative condensers. Legionella prefers to grow in t warm water like hot tubs etc. There is no vaccine for Legionella, therefore it should be prevented from attacking. The key to the prevention is that water systems of buildings should be maintained to reduce the risk of its growth. Furthermore, hot water tubs should be disinfected regularly as recommended by manufacturer.
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