At the end of this chapter the students will be able to:
– Describe general characteristics of Genus Chlamydia
– List the medically-important species of Genus Chlamydia
– Describe the virulent factor of pathogenic species of Genus Chlamydia
– Recognize diseases caused by Genus Chlamydia
– Discuss pathogenicity, clinical manifestations, laboratory diagnosis,
prevention & control of members of the Genus Chlamydia
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The family has three important human
Chlamydophila pneumoniae .
4. General characteristics
• Small, gram-negative rods with no peptidoglycan layer in cell wall
• Strict intracellular parasite of humans
• They lack the ability to produce their own ATP therefore, they use host’s ATP.
• Multiply in the cytoplasm of the host cell forming microcolonies or inclusion
• Infects nonciliated columnar, cuboidal, and transitional epithelial cells
• Two biovars associated with C. trachomatis disease: trachoma (with 15
serovars) and lymphogranuloma venereum (LGV; four serovars)
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5. Difference between EB and RB
Elementary bodies(EBs) Reticulate bodies(RBs)
Adapted for extracellular
Adapted for intracellular
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• All chlamydiae have a replicative cycle different from that of all other
• Two distinct forms:
• Elementary bodies(EBs)
• Reticulate bodies(RBs)
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• Chlamydia trachomatis
– Ocular trachoma worldwide (most common in Middle East, North Africa, India)
– LGV highly prevalent in Africa, Asia, and South America
– Humans are the sole reservoir of Chlamydia trachomatis
• Human psittacosis (ornithosis) is a zoonotic pneumonia
• is mainly a pathogen of birds. Occasionally it causes disease in humans.
– contracted through inhalation of respiratory secretions or dust from droppings
of infected birds.
• Chlamydophila pneumoniae
– infection occurs throughout the year and is spread between humans by
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9. Clinical manifestation
– Chronic, inflammatory granulomatous process of eye surface, leading to
corneal ulceration, scarring, pannus formation, and blindness
– is transmitted by personal contact, for example, from eye to eye via droplets,
by contaminated surfaces touched by hands and conveyed to the eye, or by
Adult inclusion conjunctivitis:
– Acute process with mucopurulent discharge, dermatitis, corneal infiltrates, and
corneal vascularization in chronic disease
– genital infection probably precedes eye involvement. Autoinoculation and oral-
genital contact are believed to be the routes of transmission
– infant's eyelids swell, hyperemia occurs, and copious purulent discharge
– infection acquired during passage of the infant through an infected birth canal
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– After a 2- to -3-week incubation period, the infant develops rhinitis,
followed by bronchitis with a characteristic dry cough
– Acute process involving the genitourinary tract with characteristic
mucopurulent discharge; asymptomatic infections common in women
– A painless ulcer develops at the site of infection that spontaneously
heals, followed by inflammation and swelling of lymph nodes draining
the area, then progression to systemic symptoms
– Acute LGV is seen more frequently in men, primarily because
symptomatic infection is less common in women
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– Respiratory infections: Can range from asymptomatic or mild disease
to severe, atypical pneumonia requiring hospitalization
– Atherosclerosis: C. pneumoniae has been associated with
inflammatory plaques in blood vessels; the etiologic role in this disease
– Respiratory infections: Can range from asymptomatic colonization to
severe bronchopneumonia with localized infiltration of inflammatory
cells, necrosis, and hemorrhage
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15. Table. disease by chlamydia
Species and serotype Disease
C. Trachomatis A, B, C Trachoma
Non gonococcal urethritis
Inclusion conjunctivitis of the newborn or adult
L1,L2,L3 Lymphogranuloma venerum
C. psittaci Pneumonia(psittacosis)
C. pneumoniae Acute respiratory disease
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16. Laboratory diagnosis
Smears from conjuctiva stained by Giemsa or iodine stained smears
Inclusion bodies are intracytoplasmic vacules, usually close to
nucleus, that contain replicating organism
In the early stages of the disease
inoculation of conjunctival scrapings McCoy cell cultures permits
growth of C. trachomatis.
• The diagnosis can sometimes be made in the first passage after 2–3
days of incubation by looking for inclusions by immunofluorescence
or staining with iodine or Giemsa stain.
• Infected individuals often develop antibodies in serum and in eye
• Immunofluorescence is the most sensitive method for their detection.
Lab diagnosis for Genital Infections & Inclusion Conjunctivitis
• Smears from conjuctiva, scraping of urethra, cervix or vagina stained
by Giemsa stained smears show inclusions.
They grow on McCoy and incubated at 35–37 °C for 48–72 hrs.
examined by direct immunofluorescence to visualize the cytoplasmic
Antibody rise occurs during and after acute chlamydial infection.
Because of the high prevalence of chlamydial genital tract infections
in some societies, there is a high background of antichlamydial
antibodies in the populati
serologic tests to diagnose genital tract chlamydial infections
generally are not useful.
Lab diagnosis of Lymphogranuloma Venereum
• Pus, or biopsy material may be stained, but particles are rarely
• Suspected material is inoculated into McCoy cell cultures.
• The agent is identified by morphology and serologic tests
• Immunofluorescence can be used but it is not effective
• Topical therapy is of little value.
Chlamydia trachomatis, Genital Infections & Inclusion
• Tetracyclines ,doxycycline are commonly used in nongonococcal
urethritis and in nonpregnant infected females.
• Topical tetracycline or erythromycin is used for inclusion
conjunctivitis, sometimes in combination with a systemic drug.
• The sulfonamides and tetracyclines is used, especially in the early
• Macrolides (erythromycin, azithromycin, clarithromycin)
• Tetracyclines (tetracycline, doxycycline)
• doxycycline or erythromycin
23. Prevention and control
• Improved socioeconomic conditions enhance the disappearance of
• Safe sex practices and early diagnosis and treatment of infected
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