Chlamydia pneumoniae (TWAR) - MegaMicro

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Chlamydia pneumoniae (TWAR)

Microbiology > Bacteriology > Intracellular bacteria > Chlamydia
-          Member of the genera chlamydophila in the family Chlamydiaceae
-          Taiwan acute respiratory agent (TWAR) is the single identified serotype
-          Gram-negative bacterium
-          Coccoid or rod-shaped
-          Small (0.2 – 1 µm)
-          Possesses inner and outer membranes, but does not have a peptidoglycan layer like other gram-negatives
-          No plasmid DNA
-          Obligate intracellular bacterium
-          Virulence factors:
o   Ability to enter and replicate using cellular machinery
§  Adverse effects include pro-inflammatory activation, cytokine release, and upregulation of adhesion molecules
o   Heat-shock protein 60
o   Outer membrane protein A
o   Type III secretion apparatus
-          Biphasic Life Cycle
o   Beginning with a metabolically inactive infectious form, the elementary body (EB) and a metabolically active non-infectious form, the reticulate body (RB)
o   EBs have ability to survive outside of human cells – in suitable conditions, attachment occurs and RBs are formed
o   The RBs actively divide within the host, and then differentiate into EBs to infect
-          Hosts – human epithelial cells, monocytes, macrophages, smooth muscle cells, and endothelial cells
-          Reservoir – humans, no animal reservoirs identified
o   Most commonly found in over-populated environments
-          Vectors – human-to-human spread via aerosolized respiratory secretions
-          Ubiquitous
Laboratory Diagnosis:
-          Difficult
-          Nucleic acid amplification test (NAAT)
-          Identification of the organism in culture
o   Samples should include host cells with the pathogen located within (since the organism is an obligate intracellular organism)
-          Microimmunofluorescence (MIF) test – only acceptable test for serodiagnosis
o   Single IgM titer of greater than 16 or a fourfold increase in IgM titer required for diagnosis of acute infection
-          Enzyme immunoassays also performed to detect various Ig levels to determine the specific pathogen present
Disease Manifestations
-          Commonly associated with respiratory system
-          Most infections asymptomatic or mild, causing persistent cough and malaise
-          More severe respiratory infections involve a single lobe of the lung
-          Cannot be differentiated from other atypical pneumonias (those caused by mycobacterium pneumoniae, legionella pneumophila, and respiratory viruses)
-          Bronchitis, pneumonia, sinusitis, pharyngitis, coronary artery disease
-          Association with atherosclerosis

Treatment:   Macrolides (azithromycin, erythromycin, clarithromycin), doxycycline, or levofloxacin

Related concepts

Key Words:
1.       Chlamydophila
2.       Pneumonia
3.       TWAR
4.       Elementary Body
5.       Reticulate Body

Web Links:
a.       Pathogen profile dictionary with a lot of useful information on Chlamydophila pneumoniae
Overview of Chlamydophila pneumoniae, symptoms, and treatment

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