Download Chlamydia

衣原体
Chlamydia
Introduction
Chlamydia has DNA, RNA and ribosomes.
It proliferates by binary fission.
It possesses an inner and outer membrane similar to Gramnegative bacteria.
It has lipopolysaccharide but not peptidoglycan.
It is sensitive to many antibiotics.
Introduction
Chlamydia is small obligate intracellular parasite.
Although Chlamydia can synthesize most of their metabolic
intermediates, it is unable to synthesize its own ATP. This
may be a reason for Chlamydia to be a intracellular parasitic
microbe.
Generally Chlamydia is considered to belong to bacteria.
Introduction
Chlamydia has two unique forms when it proliferates in host
cells:
elementary body (EB)
reticulate body (RB)
EB and RB
◇ EB: is smaller (0.25 to 0.3 µm
in diameter), and has dense
structure, and infectivity.
◇ RB: is larger (0.5 to 0.6 µm in
diameter), and has loose
structure, and no infectivity.
Classification
Chlamydia only has one genus with three species and
all the species can cause human diseases:
•C. trachomatis:
causes trachoma ( 沙 眼 ), urogenital
infections, conjunctivitis (结膜炎，红眼睛), pneumonia and
lympho-granuloma venereum (LGV,性病淋巴肉芽肿). Humans
are the only natural host.
•C. pneumoniae: causes bronchitis, pneumonia and sinusitis.
Humans are the only natural host.
•C. psittaci: causes pneumonia (psittacosis).
Developmental cycle
Staining methods
Gram-negative but Gram stain is not used for identification.
Giemsa stain is often used. EB is purple while RB is blue.
Staining methods
Immunofluorescence using
specific antibodies can stain
the inclusion body brightly.
沙眼衣原体
Chlamydia trachomatis
• Chlamydia trachomatis has 3 serotypes:
trachoma, LGV and mouse pneumonia.
• According to the antigenic difference of
MOMP (major outer membrane protein),
C. trachomatis subsp. trachoma has 14
serotypes and C. trachomatis subsp.
LGV has 4 serotypes.
• Chlamydia trachomatis has endotoxinlike substance and the MOMP can block
the fusion of chlamydial endosome and
cellular lysosome.
Among the 14 serotypes of
C. trachomatis subsp. trachoma:
• 4 serotypes cause trachoma
– the first cause of blindness in the world
– Transmitted by eye-hand-eye pattern through direct or
indirect (e.g., towel and toy) contact
• 12 serotypes cause inclusion conjunctivitis (e.g.,
swimming pool conjunctivitis) and non-gonococcal
urethritis (NGU)
– NGU is a common STD with or without clinical
symptoms
• 10 serotypes cause infant pneumonia
Chlamydia trachomatis subsp. LGV
◇ LGV serotype can cause lympho-granuloma venereum,
a STD that is prevalent in Africa, Asia and South America.
◇ Occasionally, LGV serotype can cause conjunctivitis.
◇ Humans are the only natural host.
Laboratory diagnosis
◇Culture is the most specific method. Specimens are
inoculated to susceptible cells and then the infected cells are
examined for the presence of inclusion bodies after staining.
◇Microscopy: directly examine in the sample smear.
◇Serological examination: Due to its parasitic character,
its specific antibody is usually low and do not distinguish
between current and past infections. So serological
examination is of little clinical importance.
◇ PCR and Southern hybridization.
Treatment and prevention
◇ Tetracyclines and erythromycin
are used for treatment.
◇ No vaccine is practically used for
prevention.
Chlamydia pneumoniae
肺炎衣原体
◇ Chlamydia pneumoniae only has one serotype and
named as TWAR
The name comes from the combination of names of the two original
isolates with the same serological examination results: strain TW-183
from Taiwan in 1965 and strain AR-39 from America in 1983.
◇ This microbe is transmitted person-to-person by
respiratory droplets.
◇ Chlamydia pneumoniae is the causative agent of
atypical pneumonia.
◇ In addition, it can cause a pharyngitis, bronchitis and
sinusitis.
◇ Culture is difficult so the serological tests are most
commonly used. A four-fold rise in specific antibody titers in
paired serum samples indicates the infection.
◇ Tetracycline and erythromycin are the choice of
antibiotics. No vaccine is available.