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Chlamydia

Chlamydia. 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.

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Chlamydia

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  1. Chlamydia

  2. 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.

  3. Chlamydia has DNA, RNA and ribosomes. • It proliferates by binary fission. • It possesses an inner and outer membrane similar to Gram-negative bacteria. • It has lipopolysaccharide but not peptidoglycan. • It is sensitive to many antibiotics.

  4. Chlamydia has two unique forms when it proliferates in host cells: elementary body (EB) reticulate body (RB)

  5. EB and RB ◇EB: issmaller (0.25 to 0.3 µm in diameter), and has densestructure, and infectivity. ◇ RB: is larger (0.5 to 0.6 µm in diameter), and has loosestructure, and no infectivity.

  6. 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).

  7. Developmental cycle

  8. Staining methods • Gram-negative but Gram stain is not used for identification. • Giemsa stain is often used. EB is purple while RB is blue.

  9. Staining methods • Immunofluorescence using specific antibodies can stain the inclusion body brightly.

  10. I. Chlamydia trachomatis

  11. 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.

  12. Chlamydia trachomatis has endotoxin-like substance and the MOMP can block the fusion of chlamydial endosome and cellular lysosome.

  13. 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

  14. Chlamydia trachomatis subsp. LGV ◇ LGVserotype can cause lympho-granuloma venereum, a STD that is prevalent in Africa, Asia and South America. ◇Occasionally,LGVserotype can cause conjunctivitis. ◇ Humans are the only natural host.

  15. Laboratory diagnosis ◇Culture isthe 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.

  16. Treatment and prevention ◇ Tetracyclines and erythromycin are used for treatment. ◇ No vaccine is practically used for prevention.

  17. II. Chlamydia pneumoniae

  18. ◇ 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.

  19. ◇ 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.

  20. III. Chlamydia psittaci

  21. ◇Chlamydia psittaci is firstly isolated from parrot. Later many birds are found to be able to carry the microbe. In birds, C. psittaci causes inapparent infection. ◇ C. psittaci can cause human disease called parrot fever (psittacosis) with fever, chill, cough and headache, which can develop into a mild pneumonia.

  22. ◇ Laboratory diagnosis is based on serological tests.

  23. ◇Tetracycline or erythromycin are the choice of curative antibiotics. No vaccine is available.

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