Download T pallidum

Spirochetes
(Spiral bacteria)
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Classification
Domain: Bacteria
Family : Spirochetaceae (free living spirochetes)
Treponemataceae (human pathogens)
Genus: Treponema
Borrelia
leptospira
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General Features

All
spirochetes
have
similar
morphological
appearance

They are all long slender, helically coiled (spiral)
gram negative bacilli around 5-250 µm in length

Obligate intracellular parasites

Contain axial filament (endoflagella) which begins
at each end of the organism and wind around it,
extending and overlapping at the mid point
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General Features

Axial filament runs between the bacterial inner
and outer membranes in the periplasmic space
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
Very actively motile

Reproduce by traverse binary fission
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Genus : Tryponema

4 spp (subspecies)
T pallidum subspecies pallidum (T pallidum)
Syphilis
T pallidum subspecies pertenue (T pertenue)
Yaws
T pallidum subspecies endemicum (T endemicum)
Endemic syphilis (bejel)
T carateum
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Pinta
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T pallidum subspecies pallidum
Morphology
Small , about 5-15 µm in length, slender gram
negative spiral bacilli
Actively motile
So thin (very difficult to be seen by gram stain)
Can only be seen using dark field illumination or
immuno-fluorescent stain
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Growth and cultural characteristics
Microaerophilic organisms , survives best in 1-4 %
O2
Never been cultured on artificial growth media or
tissue culture.
Obligate intracellular parasites and therefore cant be
transmitted by public surfaces because of its narrow
temperature and pH ranges (can not survive in
temperature higher than 42 C and their optimal pH
range is 7.2 - 7.4)
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Growth and cultural characteristics
Exposure to air, antiseptic or sunlight kill it
Invivo generation time very long about 30 hours
All spp sensitive to penicillin
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Antigenic structures
-
-
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Not widely characterized
more than 100 protein antigens
-
Outer membrane lipoproteins
-
Endoflagellar antigens
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Pathogenesis, pathology and
clinical findings
- T pallidum infection is limited to human host
(animals can only be infected experimentally)
- Infection with T pallidum cause a disease called
Syphilis
- Syphilis can be divided into two main types
Acquired syphilis
Congenital syphilis
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Pathogenesis, pathology and
clinical findings
Acquired syphilis
- Transmitted by sexual intercourse
- 3 stages
Primary stage
- Multiply locally at the site of entry
- Painless chancre lesion (painless ulcer) on skin
and mucous membrane of external genetalia
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Pathogenesis, pathology and
clinical findings
- 10-20% of cases the 1ry lesion is intra-rectal or
peri-anal or oral
- Lasts for 2-6 weeks and then recede even without
treatment (you should treat it!!!!)
- Highly infectious
spirochetes
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stage
and
lesion
rich
in
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Pathogenesis, pathology and
clinical findings
Secondary stage
- Develop 2-10 weeks after the infection
- None specific symptoms
maculo-papular rash, fatigue, fever sore throat
headaches , loss of appetite and lymphadenopathy
- Also subsides spontaneously
- Like 1ry stage, 2ry lesions are rich in spirochetes
and highly contagious
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Pathogenesis, pathology and
clinical findings
Tertiary stage
- 30 % of patents with syphilis progress to complete
cure even without treatment
- Another 30% of patents , untreated infections
remain latent (evident by positive serological
reactions)
- About 40 % of patients progress to tertiary syphilis
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Pathogenesis, pathology and
clinical findings
Tertiary stage
- Granulmatous lesions (GUMMAS) in skin , bones, joints
and liver
- Degenerative changes in CNS including syphilitic
meningitis, paralysis , difficulties in movements, stroke,
numbness and gradual blindness
- Cardiovascular syphilitic lesions (aortitis,
aneurysm an aortic valve insufficiencies
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aortic
- Not infectious stage, tryponema very rarely isolated
and lesions are attributed to hypersensitivity to organism
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Pathogenesis, pathology and
clinical findings
Congenital syphilis
- From pregnant woman to fetus through placenta
- Usually begins in the 10th to 15th weeks of
gestation
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- Consequences
• Some of the infected fetuses die and abortion
result
• Some are stillbirth at delivery
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Pathogenesis, pathology and
clinical findings
Congenital syphilis
• Some fetuses born life but die soon after birth
• Some fetuses born life but develop signs of
congenital syphilis in childhood, these include
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Varity of CNS anomalies
Deafness
Teeth deformities
Saddle nose
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Laboratory Diagnosis
• Specimen
- Tissue fluid expressed from early surface
lesions for identification of spirochetes
- Blood or serum for serology
• Direct testing
- Dark - field examination (should be
before the starting of antibiotic treatment)
- IF
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Laboratory Diagnosis
• Serology
- Two types :
- None treponemal serological tests
(detect none trponemal antigens or antibodies)
- Treponemal serological tests (detect
treponemal antigens or antibodies)
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Laboratory Diagnosis
None treponemal serological tests
- None specific tests
- Used for screening
- Look for cardiolipins (Indirect indications of the
infection with T pallidum
- Cardiolipin shares some antigenic determinants
with T pallidum
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- They indicate either active infection or healed
but not treated infection
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Laboratory Diagnosis
- Two types
VDRL (Venereal Disease Research Laboratory)
test
RPR (Rapid Plasma Reagin) test
- The only difference between the two the later
does not need a microscope to read the result
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Laboratory Diagnosis
- Ve VDRL test
+ Ve VDRL test
- Positive test is indicated by the formation of
clusters
- If positive, go with treponemal serological tests
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Laboratory Diagnosis
Disadvantages of None treponemal serology
- Not specific (false positive can occur with other
conditions such us pregnancy , HIV, TB, and
rheumatoid arthritis
- Not very sensitive in early syphilis, specially in the
first 2-3 weeks after the infection (false negative)
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Disadvantages of None treponemal serology
- Not specific (false positive can occur with other
conditions such us pregnancy , HIV, TB,
rheumatoid arthritis
- Not very sensitive in early syphilis, specially in the
first 2-3 weeks after the infection (false negative)
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Laboratory Diagnosis
Treponemal serological tests
- Indicated if non treponemal serological tests are positive
- Detect treponemal antigens or antibodies
- Remains positive for life (not useful for screening)
- Many types:
Fluorescent treponemal antibody (FTA)
Treponema pallidum particle agglutination
ELISA
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Treatment and Immunity
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-
Sensitive to penicillin ( treatment of choice)
-
If patient is allergic, tetracycline and erythromycin
can be substituted but they are generally less
effective than penicillin
-
No permanent immunity. If the disease is treated,
the individual again becomes fully susceptible to
re-infection
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Other Treponema subspecies
• T pallidum subspecies pertenue
• T pallidum subspecies endimicum
Yaws
Bejel
- Non sexually transmitted diseases
- Affect children in hot tropical countries
- 1ry lesion is an ulcerating macule or papule
on arms and legs. Complications rare
- Yaws is a variant of syphilis (????)
- Sensitive to penicillin ( treatment of choice)
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Other Treponema subspecies
• T carateum
Pinta
- Non sexually transmitted disease
- Affect all age groups in Mexico and South
America (restricted to dark skinned people)
- 1ry lesion is non ulcerating macule on
exposed areas changes later on to hyperpigmented
lesions. Complications rare
- Diagnosis and treatment like syphilis
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