Mycoplasma pneumoniae

Diagnosis

Indications for Testing

  • Viral pneumonia presentation with persistent cough

Laboratory Testing 

  • PCR – rapid test to identify M. pneumoniae
    • Increased sensitivity if sputum is tested and infection is in early stage (first 21 days after onset)
    • Probably most sensitive test to use, especially in adults who may not mount significant IgM levels early in infection
  • IgG, IgM by ELISA, EIA, complement fixation – usually requires acute and convalescent samples
    • Not effective in early diagnosis
  • Culture – inadequate for acute diagnosis
    • Not recommended; bacteria are relatively fastidious and require a long incubation (up to 4 weeks)
  • Consider concurrent serology for C. pneumoniae, urinary antigen detection for Legionella, viral studies (eg, DFA panel for respiratory viruses)

Imaging Studies

  • Chest radiography – patchy, unilateral infiltrates or diffuse, bilateral interstitial process

Differential Diagnosis

Clinical Background

Mycoplasmas, the smallest self-replicating organisms, include M. pneumoniae (pneumonia), M. genitalium, and Ureaplasma urealyticum (urethritis). M. pneumoniae is a common cause of community-acquired pneumonia.

Epidemiology

  • Prevalence
    • Responsible for 15-20% of all community-acquired pneumonia; higher rates among school children and people in closed populations (military recruits)
      • 2-5% of patients require hospitalization as compared with 15-20% hospitalization rates for other causes of pneumonia
  • Transmission – respiratory droplet
    • Most common in U.S. during late summer to early fall

Organism

  • M. pneumoniae
    • Flask-shaped bacteria with no true cell wall and a very small genome (816 kilobase pairs)
    • Facultative intracellular parasite
    • Cultivation in vitro is difficult
      • Fastidious nature
      • Heavily dependent on externally supplied growth factors (by host organism or in culture medium)
      • Limited metabolic capacity inherent in small genome

Clinical Presentation

  • Most infections are mild and often indistinguishable from other viral and atypical bacterial pathogens
  • Initial symptoms – malaise, myalgias, sore throat, headache (retro-orbital), ear pain, and fever
    • Patients who progress to pneumonia may have additional symptoms, including chills, chest pain, shortness of breath, nausea, vomiting, diarrhea
  • Pulmonary infection
    • Dry, nonproductive cough occurs 3-5 days after onset of initial nonspecific symptoms
      • Cough may produce mucopurulent sputum later in illness
    • Patients usually seek medical attention after 5-7 days
      • Cough may become paroxysmal and nocturnal
    • Cough may persist several weeks following resolution of constitutional symptoms
    • Pleural effusions more common in severe disease
  • Extrapulmonary manifestations of M. pneumoniae infections
    • Syndromes caused by spread of organism
      • Bullous hemorrhagic otitis
      • Arthritis
      • Acute respiratory distress syndrome
      • Myocarditis
      • Encephalitis/meningitis
      • Sinusitis
    • Immunologically mediated syndromes

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Mycoplasma pneumoniae by PCR 0060256
Method: Qualitative Polymerase Chain Reaction

Diagnose M. pneumoniae infection

Distinguish M. pneumoniae from other viruses and atypical pathogens (Chlamydia pneumoniae, Bordetella pertussis, Legionella)

Throat swab specimens are preferred

 
Mycoplasma pneumoniae Antibodies, IgG & IgM 0050399
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Diagnose M. pneumoniae infection; requires both acute and convalescent samples (2-4 weeks apart)

   
Respiratory Viruses DFA with Reflex to Respiratory Virus Mini Panel by PCR 2002565
Method: Direct Fluorescent Antibody Stain/Qualitative Polymerase Chain Reaction

Screen for respiratory viruses

If DFA is negative or inadequate for influenza, Respiratory Virus Mini Panel by RT-PCR will be added

   
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Mycoplasma pneumoniae Antibody, IgM 0050398
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Low IgM antibody levels may persist more than 12 months post-infection

Mycoplasma pneumoniae Antibody, IgG 0050397
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Legionella Species, Culture 0060113
Method: Culture/Identification
Legionella Species by Qualitative PCR 2010125
Method: Qualitative Polymerase Chain Reaction
Legionella pneumophila Antigen, Urine 0070322
Method: Qualitative Enzyme-Linked Immunosorbent Assay