questions 3

Legionnaires' Disease

Topic updated on 06/12/17 7:13pm

  • A 65-year-old male presents with a 5 day history of high fever, cough, and diarrhea after returning from a 2 week cruise to the Carribean. Patient has COPD with a 30 pack-year history of cigarette smoking. Temperature is 100.2°F (39°C), respirations are 24/min, BP is 100/60mmHg, pulse is 90/min and oxygen saturation 87% on room air. Chest exam reveals dull percussion notes at the left lung base. Chest radiograph reveals left lobar infiltrate, with patchy opacities on the right. Complete metabolic panel revealed a hyponatremia of 130 mEq/L, serum creatinine of 1.0 (baseline) and elevated AST/ALT.  Complete blood count showed a leucocytosis.  A urinary antigen test was positive. Sputum culture results are being awaited, although there only neutrophils detected on Gram stain.
  • Classification
    • bacteria
      • other gram-negative
        • Legionella
          • L. pneumophila 
  • Legionnaires' disease 
    • severe atypical pneumonia
      • "fever, cough, diarrhea, especially in a smoker"
    • high fever (>39°C)
    • low heart rate
    • confusion
    • hyponatremia(<130mEq/L)
    • diarrhea
      • although no bacteria seen in GI tract
  • Pontiac fever
    • mild flu-like syndrome
  • Other etiologies of atypical pneumonia
    • Mycoplasma
    • Chlamydia
  • Typical community acquired pneumonia
    • S. pneumoniae
  • Labs are essential because clinical presentation is nonspecific, LFTs may be elevated
  • 2 most important tests
    • culture
      • weakly gram-negative
      • stain with silver instead
    • urinary antigen test
      • avoids need for sputum sample
      • remains positive even after empiric antibiotic therapy
      • available in hours vs. 3-5 days for culture
      • specific for serogroup 1 only
        • by far the most common serogroup
  • Also used
    • DFA staining of sputum
    • serology
    • PCR
  • Erythromycin, azithromycin, levofloxacin
  • Penicillin is not effective
Prognosis, Prevention and Complications
  •  Prognosis
    • good if treated promptly with antibiotics
    • worse in the immunocompromised
  • Prevention
    • routine cultures of potential water sources(e.g hospitals)
    • monochloramine disinfection of community water supplies
    • decontaminate air conditioners routinely
  • Complications
    • rare, seen more in immunocompromised patients
      • myocarditis, prosthetic valve endocarditis


Qbank (2 Questions)

(M2.ID.13) A 77-year-old woman presents to the infirmary with cough, fever, and diarrhea. She denies vomiting. She is on a cruise ship and developed her symptoms while on the trip. Other passengers have been having similar symptoms. She has been progressively getting worse over the past several days. She is a smoker and has a history of chronic obstructive pulmonary disease. She has long standing hypertension, which has resulted in chronic renal insufficiency. She has not been hospitalized in the past several years. Her vital signs are temperature of 38.9 degrees celsius, heart rate 75 beats per minute, blood pressure of 125/85, respiratory rate of 22, and oxygen saturation of 89% on room air. On physical examination, she has crackles bilaterally. Complete metabolic profile is significant for serum sodium of 133, creatinine of 2.5 (which is at her baseline), and elevated AST/ALT. Complete blood count yields leukocytosis. Regarding the illness affecting this patient and other individuals on the ship with similar symptoms, what would be the most likely means of diagnosis and treatment? Topic Review Topic

1. Diagnosis with urine antigen or culture and treatment with azithromycin or levofloxacin
2. Diagnosis with blood cultures and treatment with nafcillin
3. Diagnosis with blood cultures and treatment with vancomycin
4. Diagnosis with nasal swab PCR and supportive care
5. Diagnosis with FTA-abs and treatment with penicillin

(M2.ID.16) A 67-year-old man presents with a hacking cough and fever. His health has been declining over the past several days. He is a smoker and has a history of chronic renal insufficiency. He works in a green house. He has no recent hospitalizations. His vital signs are temperature of 39 degrees celcius, heart rate 70 beats per minute, blood pressure of 140/90, respiratory rate of 22, and oxygen saturation of 90% on room air. On physical examination, he has diffuse crackles in both lungs. A basic metabolic profile and complete blood count are performed and reveal hyponatremia and leukocytosis. Which of the following is true of this illness? Topic Review Topic

1. The illness will respond to amoxicillin
2. One would also expect liver function test abnormalities
3. This illness never presents with gastrointestinal symptoms
4. The same pathogen may cause epiglottitis in children
5. If the disease progresses to sepsis, it will cause black lesions on the skin

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