Previous
Next

Mycoplasma pneumoniae

15
Watch Video

Mycoplasma pneumoniae 

  • Characteristics
    • Pleomorphic
    • No cell wall
      • Cell membrane contains cholesterol
      • Not visualizable by Gram stain
      • Not susceptible to beta-lactam antibiotics
    • Grows on Eaton agar
  • Transmission
    • Respiratory droplets
    • Occurs frequently in young (<30 y.o.) individuals living in close contact
      • College students, military recruits, and prisoners
  • Presentation
    • atypical “walking pneumonia”
      • Insidious onset, fever, headache, nonproductive cough
      • Caused by tracheobronchitis: inflammatory infiltration of airways
      • patchy/diffuse interstitial infiltrate on CXR
        • CXR looks worse than patient presentation would suggest
    • Associated with
      • Cold agglutinins
        • IgM antibodies agglutinate RBCs under cold temperatures
          • Due to similarity between antigens in Mycoplasma and RBC membranes (molecular mimicry)
        • Causes hemolytic anemia
          • Complement-mediated attack of RBCs with bound IgM
          • Presents with positive Coombs test, elevated LDH, elevated reticulocyte count
          • Spontaneous resolution over time
      • Erythema multiforme (EM)
        • Red rash that can evolve into target lesions
          • Caused by autoimmune response to antigens deposited in skin
      • Stevens-Johnson syndrome
      • Culture-negative endocarditis
  • Treatment
    • Macrolides
    • Doxycycline
    • Fluoroquinolone
      • Respiratory fluoroquinolones used like levofloxacin or moxifloxacin
    • Penicillin ineffective since it has no cell wall