Mycoplasma pneumoniae

Mycoplasma pneumoniae

 

Mycoplasmas, the smallest self-replicating organisms, include M. pneumoniae (pneumonia), M. genitalium and Ureaplasma urealyticum (urethritis).

  • As intracellular parasites (prokaryotes), they depend on host for nutrients
  • Cultivation in vitro is difficult due to fastidious nature

M. pneumoniae

  • Frequent cause of upper and lower respiratory tract infection
  • Responsible for 15-20% of all cases of pneumonia, higher rates among school children
    • Only 2-5% of patients require hospitalization (15-20% hospitalization rates for other causes of pneumonia)
  • Infection spreads slowly among family members and throughout communities
  • Manifestations
    • Often indistinguishable from other viral and atypical bacterial pathogens
    • Initial symptoms - malaise, myalgias, sore throat, headache (retro-orbital), ear pain and fever
    • In patients who progress to pneumonia - chills, chest pain, nausea, vomiting and diarrhea may occur
    • Dry, nonproductive cough occurs 3 - 5 days after onset of initial nonspecific symptoms
      • Later, cough may produce mucopurulent sputum
      • Patients usually seek medical attention on days 5-7, when cough may become paroxysmal and nocturnal
      • Cough may persist several weeks following resolution of constitutional symptoms
  • Extrapulmonary manifestations of M. pneumoniae infections
    • Immunologically-mediated syndromes
      • Skin rashes
      • Erythema nodosum or erythema multiforme
      • Anemia
      • Thrombocytopenia
      • Guillain-Barré syndrome
    • Syndromes caused by the spread of organism
      • Bullous hemorrhagic otitis
      • Arthritis
      • Acute respiratory distress syndrome (ARDS)
      • Myocarditis
      • Encephalitis/meningitis

Diagnosis

  • Clinical signs:
    • Crackles or wheezes on auscultation of the chest
  • Chest radiograph findings - patchy, unilateral infiltrates or diffuse, bilateral interstitial process
  • Since pneumonia caused by M. pneumoniae may be indistinguishable from viral causes and other atypical pathogens such as Chlamydia pneumoniae, Bordetella pertussis, Legionella and others, laboratory confirmation is appropriate for patient management

See Also