1. family Chlamydiaceae

2. Objectives
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
pathogens:
 Chlamydia trachomatis
 Chlamydophila psittaci
 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
bodies.
• 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)
Small Large
Infectious noninfectious
Adapted for extracellular
survival
Adapted for intracellular
growth
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6. …cont’d
• All chlamydiae have a replicative cycle different from that of all other
bacteria.
• Two distinct forms:
• Elementary bodies(EBs)
• Reticulate bodies(RBs)
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7. Epidemiology
• Chlamydia trachomatis
– Ocular trachoma worldwide (most common in Middle East, North Africa, India)
with blindness
– 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
person-to-person contact
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8. Virulence factor
 Intracellular replication
 Exotoxin and endotoxin
 Prevents fusion of phagosome lyzozome
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9. Clinical manifestation
Chlamydia trachomatis
Trachoma:
– 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
flies
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
Neonatal conjunctivitis:
– infant's eyelids swell, hyperemia occurs, and copious purulent discharge
appears
– infection acquired during passage of the infant through an infected birth canal
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10. …cont’d
Infant pneumonia:
– After a 2- to -3-week incubation period, the infant develops rhinitis,
followed by bronchitis with a characteristic dry cough
Urogenital infections:
– Acute process involving the genitourinary tract with characteristic
mucopurulent discharge; asymptomatic infections common in women
Lymphogranuloma venereum:
– 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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11. …cont’d
Chlamydophila pneumoniae
– 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
is controversial
Chlamydophila psittaci
– Respiratory infections: Can range from asymptomatic colonization to
severe bronchopneumonia with localized infiltration of inflammatory
cells, necrosis, and hemorrhage
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14. Chlamydial cervicitis
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15. Table. disease by chlamydia
Species and serotype Disease
C. Trachomatis A, B, C Trachoma
D-K Cervicitis
Epididymitis
Non gonococcal urethritis
Proctitis
Salpingitis
Infant pneumonia
Inclusion conjunctivitis of the newborn or adult
L1,L2,L3 Lymphogranuloma venerum
C. psittaci Pneumonia(psittacosis)
C. pneumoniae Acute respiratory disease
Bronchitis
Pharyngitis
Pneumonia
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16. Laboratory diagnosis
Microscopic examination
 Smears from conjuctiva stained by Giemsa or iodine stained smears
show inclusions
 Inclusion bodies are intracytoplasmic vacules, usually close to
nucleus, that contain replicating organism
Culture
 In the early stages of the disease
 inoculation of conjunctival scrapings McCoy cell cultures permits
growth of C. trachomatis.
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17. …cont’d
• 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.
Serology
• Infected individuals often develop antibodies in serum and in eye
secretions.
• Immunofluorescence is the most sensitive method for their detection.
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18. …cont’d
Lab diagnosis for Genital Infections & Inclusion Conjunctivitis
Microscopic examination
• Smears from conjuctiva, scraping of urethra, cervix or vagina stained
by Giemsa stained smears show inclusions.
Culture
 They grow on McCoy and incubated at 35–37 °C for 48–72 hrs.
 examined by direct immunofluorescence to visualize the cytoplasmic
inclusions.
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19. …cont’d
Serology
 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.
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20. …cont’d
Lab diagnosis of Lymphogranuloma Venereum
Microscopic examination
• Pus, or biopsy material may be stained, but particles are rarely
recognized.
Culture
• Suspected material is inoculated into McCoy cell cultures.
• The agent is identified by morphology and serologic tests
Serology
• Immunofluorescence can be used but it is not effective
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21. Treatment
Trachoma
• azithromycin
• Topical therapy is of little value.
Chlamydia trachomatis, Genital Infections & Inclusion
Conjunctivitis
• 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.
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22. …cont’d
Lymphogranuloma Venereum
• The sulfonamides and tetracyclines is used, especially in the early
stages.
Chlamydophila pneumoniae
• Macrolides (erythromycin, azithromycin, clarithromycin)
• Tetracyclines (tetracycline, doxycycline)
C. psittaci
• doxycycline or erythromycin
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23. Prevention and control
• Improved socioeconomic conditions enhance the disappearance of
endemic trachoma.
• Safe sex practices and early diagnosis and treatment of infected
persons.
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