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The role of atypical pathogens in community-acquired pneumonia

Thomas J Marrie1, Nicholas Costain, Bernard La Scola

  • 1Faculty of Medicine, Dalhousie University, ClinicalResearch Centre, 5849 University Ave., Halifax, Nova Scotia, Canada. t.marrie@dal.ca

Seminars in Respiratory and Critical Care Medicine
|June 22, 2012
PubMed

Insights

Atypical pneumonia classification is evolving, moving beyond historical definitions. This review categorizes pathogens and highlights viral pneumonia diagnosis using multiplex PCR and procalcitonin assays for better patient management.

Area of Science:

  • Infectious Diseases
  • Pulmonology
  • Microbiology

Background:

  • The term 'atypical pneumonia' originated in 1938 and commonly referred to Mycoplasma pneumoniae, Legionella, and Chlamydophila pneumoniae by the 1970s.
  • Historically, 'atypical' encompassed all pneumonias not caused by classic bacteria, though many now advocate for abandoning this term.
  • Current understanding necessitates a re-categorization of pneumonia etiologies, including viral and emerging pathogens.

Purpose of the Study:

  • To review and categorize pathogens responsible for atypical pneumonia, distinguishing between conventional, viral, and emerging agents.
  • To emphasize the diagnostic advancements in identifying viral pneumonia.
  • To discuss the utility of procalcitonin assays in differentiating viral from bacterial pneumonia for improved clinical decision-making.

Main Methods:

  • Categorization of atypical pneumonia pathogens into conventional, viral, and emerging groups.
  • Emphasis on multiplex polymerase chain reaction (PCR) for identifying viral pneumonia agents.
  • Utilization of sensitive procalcitonin assays to distinguish between viral and bacterial pneumonia.

Main Results:

  • Multiplex PCR enables precise identification of causative agents in viral pneumonia.
  • Procalcitonin assays effectively differentiate viral from bacterial pneumonia at early clinical stages.
  • This diagnostic approach allows for timely classification of pneumonia etiology (bacterial or viral) upon hospital admission or emergency department discharge.

Conclusions:

  • The classification of pneumonia is shifting towards etiological identification, particularly differentiating viral from bacterial causes.
  • Advanced diagnostic tools like multiplex PCR and procalcitonin assays are crucial for accurate and timely pneumonia diagnosis.
  • Accurate etiological classification, whether definite or probable, improves patient management and treatment strategies for pneumonia.

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