Updated: 9/16/2020

Mycoplasma pneumoniae

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Snapshot
  • An 18-year-old college student presents to the student health clinic with a mild fever, headache, fatigue, and a dry, non-productive cough. He says that his symptoms started about 3 weeks ago and have not improved. The physician obtains a chest radiograph, which shows a pattern of diffuse interstitial infiltrates that appears worse than the patient’s physical appearance. The patient is prescribed azithromycin for his infection.
Introduction
  • Classification
    • Mycoplasma pneumoniae
      • pleomorphic
      • no cell wall
      • cell membrane contains cholesterol
      • causes an atypical “walking” pneumonia
  • Epidemiology
    • demographics
      • more common in patients < 30 years of age
    • risk factors
      • frequently seen among young individuals living in close contact
        • college students living in dormitories
        • military recruits
        • prisoners
  • Pathogenesis
    • transmission
      • respiratory droplets
    • Mycoplasma pneumoniae attaches to the respiratory epithelium, destroys the superficial layer of respiratory epithelial cells, and reduces the ability of the upper airways to clear themselves
  • Associated conditions
    • cold autoimmune hemolytic anemia 
    • erythema multiforme
    • acute interstitial nephritis
    • bacterial myocarditis
Presentation
  • Symptoms 
    • mild fever 
    • headache
    • non-productive cough
  • Physical exam
    • non-productive cough
    • bilateral wheezing may be heard on auscultation
    • macropapular or vesicular rash
Imaging
  • Chest radiography
    • patchy or diffuse interstitial infiltrates
    • chest radiograph often looks more severe than the patient’s actual presentation
Studies
  • Labs
    • detection of high titer of cold agglutinins (IgM antibodies) on serology 
      • cold agglutinin production peaks during the third week of infection
  • Microbiological studies
    • growth on Eaton agar
    • not seen on Gram stain due to lack of a cell wall
  • Making the diagnosis
    • based on clinical presentation and laboratory studies
Differential
  • Viral infection
    • distinguishing factor
      • would not produce high titer of cold agglutinins (IgM)
  • Chlamydophila pneumoniae infection
    • distinguishing factor
      • d3 cytoplasmic inclusions (reticulate bodies) seen on Giemsa or fluorescent antibody-stained smear
  • Legionella infection
    • distinguishing factor
      • different demographic
        • more common in smokers and patients with chronic lung disease
      • grows on charcoal yeast extract agar buffered with cysteine and iron
Treatment
  • Medical
    • macrolide antibiotics (especially Azithromycin)
    • doxycycline
    • fluoroquinolones
Complications
  • Autoimmune hemoltyic anemia
  • Acute interstitial nephritis
  • Bacterial myocarditis
 

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(M1.MC.13.16) A 14-year-old female notes that while her fever, malaise, and a sore throat have dissipated a week ago, her hacking cough persists. A chest radiograph (Figure A) demonstrates a streaky infiltrate in her right lung that appears much worse than the symptoms she is experiencing. A cold agglutination test conducted on her blood shows clumping together when placed at 4 degrees Celsius. Which of the following medications would best treat the agent causing her cough? Tested Concept

QID: 101475
FIGURES:
1

Vancomycin

6%

(21/344)

2

Isoniazid

9%

(32/344)

3

Ampicillin

6%

(21/344)

4

Azithromycin

76%

(261/344)

5

Pyrazinamide

1%

(3/344)

L 3 E

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