Mycoplasma pneumoniae

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