Chlamydia pneumoniae (TWAR) - MegaMicro

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Chlamydia pneumoniae (TWAR)

Micro > Bacteriology > Intracellular bacteria > Chlamydia
 
Background:
 
-          Member of the genera chlamydophila in the family Chlamydiaceae
 
-          Taiwan acute respiratory agent (TWAR) is the single identified serotype
 
 
Structure:
 
-          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
 
 
Pathobiology:
 
-          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
 
 
Epidemiology:
 
-          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:
1.       http://www.ppdictionary.com/bacteria/bwum/pneumoniae.htm#fig2
a.       Pathogen profile dictionary with a lot of useful information on Chlamydophila pneumoniae
2.       http://chlamydia-pneumoniae.org
Overview of Chlamydophila pneumoniae, symptoms, and treatment


 
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