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Chlamydia
Filename: Chlamydia.ppt
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Chlamydia
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Chlamydia
Obligate intracellular coccoid parasites
 contain DNA and RNA, and ribosomes
 lack ATP, biosynthetic pathways
 cell wall but peptidoglycan absent 
– use disulfide bonds

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non motile
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Obligate Parasites

Obligate intracellular parasites of mammals
and birds
– not transmitted by arthropods.
– incorrectly called the PLT viruses or Bedsonia or
basophilic viruses,

Multiply in the cytoplasm of the host cell.
– generally epithelial cells
– Basophilic inclusions
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Similar to Viral Infections
The methods used to study Chlamydia
are those of the virologist rather than
the bacteriologist.
 The clinical features, pathogenesis,
pathology and epidemiology of
chlamydial infections are similar to
those of viral infections.

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Energy Parasites
The cells can synthesize DNA, RNA and
protein.
 No flavoproteins or cytochromes.
 lack of ATP-generating ability
 need to obtain ATP from the host cell.

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Three species:
C. trachomatis
C. psittaci
C. pneumoniae
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Ecology
Chlamydia form two main ecological groups.
 Infect only humans

– Subgroup A
– trachoma, inclusion conjunctivitis, and
lymphogranuloma venereum

Zoonotic Infections
– Subgroup B
– Respiratory tract infections
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Zoonotic Infections
transmitted to man
 About 100 species of birds are naturally
infected with chlamydia.

– 71 species of parrots
– finches, pigeons, chickens, ducks, turkeys
and seabirds.
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C trachomatis
Trachoma
conjunctivitis
proctitis
urethritis
salpingitis
Lymphogranuloma venereum
C psittaci & C
pneumoniae
Upper respiratory infection
Bronchitis
Pneumonia
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Chlamydial Morphologies

Elementary body
– 0.25 - 0.3 um diameter
– electron-dense nucleoid
– Released from ruptured infected cells.
Human to human
– & bird to human.

Reticulate Body
– Intracytoplasmic form 0.5 - 1.0 um
– Replication and growth. ( Inclusion body )
– without a dense center.
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Developmental Cycle of
Chlamydia
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C trachomatis elementary bodies
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C trachomatis inclusions
Glycogen Inclusions
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Subgroups

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Subgroup A
Mammalian parasites
Compact inclusions
Glycogen synthesized
Folates synthesized


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– Sensitive to D-cycloserine

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Restricted host range
Chlamydia trachomatis
Subgroup B
Primarily bird parasites
Diffuse inclusions
Glycogen not synthesized
Folates not synthesized
– Resistant to D-cycloserine

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Broadening of host range
Chlamydia psittaci
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Evolution of Chlamydia
Gram-negative cocci
 Facultative intracellular parasites of mammals
 Obligate intracellular parasites
 Host range restricted to rodents
 Restricted virulence (compact inclusions)
 Folates synthesized (sulfonamide susceptible)
 Glycogen synthesized and deposited in
inclusions
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Conjunctivitis

Inclusion conjunctivitis:
– Transmitted by infectious secretions of the
genitourinary tract
– autoinoculation

Infantile conjunctivitis:
– Acquired in the birth canal -- 5-12 days
after birth
– most common type of conjunctivitis
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Antibiotic prophylaxis: erythromycin,
tetracycline.
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Chlamydial Infection of
Ocular Conjunctiva
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Trachoma

infection of conjunctival epithelial cells.
– subepithelial infiltration of lymphocytes.
– Infected epithelial cells contain cytoplasmic
inclusion bodies
– Cell infiltrations to cornea cause clouding
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Trichiasis: abnormal inward growth of
eyelashes.
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Predisposing factors:
climate - hot , dry
 shortage of water
 standards of hygiene low
Transmitted by flies, dirty towels, fingers,
cosmetic eye pencils.
Initial infection in childhood mostly by 1015 years of age.
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Trachoma
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Almost six million people have become blind
and another 540 million almost 10% of the
world’s population are at risk
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Trachoma Incidence
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Chlamydia trachomatis
Clinical disease
lymphogranuloma venereum
 nongonoccal urethritis (NGU)
 epididymitis
 salpingitis
 mucopurulent cervicitis
 pelvic inflammatory disease (PID)
 Reiter's syndrome
 neonatal chlamydia
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Chlamydia: Rates by Gender
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Chlamydia Symptoms In Men
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Symptoms usually appear
between 7 and 28 days after
infection, usually with mild
burning when urinating, a
more frequent need to
urinate, and a white
discharge from the penis.
Occasionally, blood may
appear in the urine. The
symptoms occur most
frequently in the morning.
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Erythematous meatus and
urethra with balanitis
Hyperlink to original
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Chlamydial Urethritis in Males
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Nongonococcal urethritis (NGU) Reiter's syndrome
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Swollen, painful right knee in which needle
aspiration for synovial fluid was performed
(yellow discoloration from the betadine prep)
Hyperlink to original
site
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Lymphogranuloma venereum LGV
200 reported cases per year.
 Incubation period is 5 to 20 days.
 Lesion: Transient vesicles on penis or
vagina that are often unnoticed and
patients do not usually seek medical
advice.
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Bilateral inguinal adenopathy
with overlying erythema
30Roberts MD
R
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LGY: "Groove sign"

Pompart's
ligament is
preserved despite
the involvement of
multiple inguinal
nodes
R Roberts MD
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LGV: Microscopy

lymph node shows
both necrosis and
granulomatous
reaction (dimorphic
necrotizing
granulomatous
reaction)
R Roberts MD
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Chlamydia pneumoniae
This bacterium was first recognized in
1983 as a respiratory pathogen, after
isolation from a college student with
pharyngitis.
 Pneumonia or bronchitis, gradual onset
of cough with little or no fever. Less
common presentations are pharyngitis,
laryngitis, and sinusitis.
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Incidence
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Each year an estimated 50,000 adults
are hospitalized with pneumonia in the
United States. The overall incidence is
unknown.
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Transmission
Person-to-person transmission by respiratory
secretions.
 Risk Groups
 All ages at risk but most common in schoolage children. By age 20 years, 50% of
population have evidence of past infection.
Reinfection throughout life appears to be
common.
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C. pneumoniae Associations
Associated with Heart Disease
 infection may be associated with

– atherosclerotic vascular disease

Proposed Associations
– Alzheimer's diseases, asthma, and reactive
arthritis
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Treatment Chlamydia
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Adults Conjunctival,
urethral, cervical, rectal:
– Azithromycin 1 gm x 1
dose
– Doxycycline 100 mg BID
for 7 days
– Ofloxacin 300 mg po BID
for 7 days
– Erythromycin 500 mg QID
for 7 days
– Amoxacillin 500 mg TID
7-10 days
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Children < 45 kg,
urogenital & rectal:
– erythromycin 50
mg/kg/day in 4 doses for
10-14 days
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Neonates (ophthalmia,
infants born to infected
mothers):
– erthromycin 50
mg/kg/day in 4 doses for
10-14 days
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Chlamydia Antigens
Antigens: group specific & species specific
 Major outer membrane protein
(cysteine-rich)
 Eucaryotic cell binding protein
Host response: damage to specific tissues
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Laboratory Diagnosis

Isolate the organism from infected tissue.
– Inoculate the yolk sac of seven-day chick embryos
– Inoculate McCoy human cells.
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Characteristic cytoplasmic inclusion bodies in
infected cells.
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Immunofluorecent tests
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Microimmunofluorescent tests
– patients with eye infections
– Check tears for the presence of antichlamydia antibody.
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Direct immunofluorescence
– of conjunctive cells with fluorescein conjugated monoclonal antibody is sensitive
and specific.
– In neonatal conjunctivitis and early trachoma
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Serological diagnosis:
Immunofluorecent tests
 Delayed Type Skin Reaction
 Antibodies to Family antigen
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FREI Test
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Delayed-type skin reaction to killed
organisms in genitourinary infections
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Antibodies to Family antigen
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Rising titer of antibody against the
chlamydial family antigen in lung
infections.
– Complement fixation test
– Fluorescent antibody test.
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DONE!!!
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