A 65-year-old man returned home to New York from a business trip to Georgia. He presented with fever with chills and rigors. He also had a cough, which produced moderate amounts of purulent sputum. He was brought to the emergency room. His chest X ray showed patchy infiltrates on both the lung fields. Gram stain of the sputum revealed polymorphonuclear leukocytes and no organisms.

1. What is the clinical diagnosis?
1. Streptococcal pneumonia
2. Hospital acquired pneumonia
3. Myocardial Infarction
4. Legionnaire’s Disease

Answer: The answer is (d). Legionnaire’s disease is characterized by a pneumonia demonstrating patchy infiltrates in the lung fields and no organisms in the sputum. Outbreaks have been associated with contaminated water sources such as shower heads, faucets and air conditioning cooling towers.

2. Patients who are susceptible to this disease are:
1. Patients who are immunocompromised
2. Patients who are on anti seizure medications
3. Patients who have chronic liver diseases
4. Left to right intracardiac shunts.

Answer: The answer is (a). Immunocompromised hosts are susceptible to Legionnaire’s disease. Other subgroups of people susceptible to this disease are chronic smokers, patients with chronic lung diseases, patients on long term steroids and those on anti cancer chemotherapy.

3. Culture on charcoal-yeast extract agar confirms the diagnosis. The specific characteristics of the organism isolated include all except
1. Positive Dieterle’s Silver staining
2. Direct fluorescent antibody staining
3. Acid fast staining
4. Belongs commonly to serotype 1.

Answer: The answer is (c). Legionella pneumophila is the organism, which is isolated by the charcoal-yeast extract agar. This organism is characterized by staining by Dieterle’s Silver staining, by direct fluorescent antibody staining. Most common serotype of Legionella pneumophila, which causes Legionnaire’s disease, is serotype 1. The organism is not acid fast.

4. Treatment of this condition includes:
1. Levofloxacin 500 mg daily orally for 15 days
2. Ampicillin 1 g intravenously daily
3. Third generation cephalosporins
4. Rifampicin 300 mg daily for 10 days

Answer: The answer is (a). Levofloxacin 500 mg daily orally or intravenously for 10-14 days, Azithromycin 500 mg followed by 250 mg daily orally or intravenously for 10-14 days or Clarithromycin 500 mg orally twice daily may be used for treatment. Azithromycin is also useful as a five-day regimen.