Chlamydia pneumoniae (TWAR)

Clin Microbiol Rev. 1995 Oct;8(4):451-61. doi: 10.1128/CMR.8.4.451.


Chlamydia pneumoniae (TWAR) is a recently recognized third species of the genus Chlamydia that causes acute respiratory disease. It is distinct from the other two chlamydial species that infect humans, C. trachomatis and C. psittaci, in elementary body morphology and shares less than 10% of the DNA homology with those species. The organism has a global distribution, with infection most common among children between the ages of 5 and 14 years. In children, TWAR infection is usually mild or asymptomatic, but it may be more severe in adults. Pneumonia and bronchitis are the most common clinical manifestations of infection, and TWAR is responsible for approximately 10% of cases of pneumonia and 5% of cases of bronchitis in the United States. The microimmunofluorescence serologic assay is specific for TWAR and can distinguish between recent and past infections. The organism can be isolated in cell culture; however, PCR techniques have recently facilitated its detection in tissues and clinical specimens.

Publication types

  • Review

MeSH terms

  • Adult
  • Animals
  • Anti-Bacterial Agents / therapeutic use
  • Bacterial Outer Membrane Proteins / chemistry
  • Child
  • Chlamydia Infections / complications
  • Chlamydia Infections / diagnosis*
  • Chlamydia Infections / epidemiology
  • Chlamydia Infections / microbiology*
  • Chlamydophila pneumoniae* / chemistry
  • Chlamydophila pneumoniae* / classification
  • Chlamydophila pneumoniae* / genetics
  • Chlamydophila pneumoniae* / immunology
  • Disease Models, Animal
  • Genes, Bacterial
  • Haplorhini
  • Humans
  • Mice
  • Rabbits


  • Anti-Bacterial Agents
  • Bacterial Outer Membrane Proteins