Bacteriology
Spirochetes
Three important genera:
1. Treponema
2. Borrelia
3. Leptospira
Treponema pallidum
Causes syphilis
Organism:
- Spirochetes with 6-14 regularly spaced spirals
- Its length is the length of RBC
- Has characteristic motility
- Can not be cultured in vitro
- In whole blood stored at 4
o
C. trep remain viable for 24 hrs.
which is of great importance in blood transfusions
- Drying kills trep rapidly as does elevation of temperature
(42
o
C)
- Can not be stained by the biological stains because it is
very thin.
- T. pallidum produce hyaluronidase
breakdown of
hyaluronic acid
enhance invasiveness of tissue.
- Cardiolipin: is an important component of T. pallidum
antigen that enhance reagin production in the patient's
serum which is antibody-like substance.
- Spirochetes are very thin, so they can not be seen unless
using.
Silver impregnation Dark-field
↓ illumination
Deposit to increase ↓
Its diameter
↓ notice character motility
Visible under microscope
- It posses Endoflagella for its movement
Pathogenesis and pathology
- Syphilis is sexually transmitted disease (STD) with
incubation period about 3 weeks.
- Stages of syphilis:
Primary stage:
Here a primary lesion develops on the genitalia or perianal sites
where T. Pallidum multiply at the sites of entery in skin or
mucous membranes of the gentalia.
The lesion (chancre) is a papule that will breakdown forming
painless ulcer (hard chancre) (in 6 weeks)
The regional lymph nodes become enlarged
Secondary stage
- 6-8 weeks after primary stage
- Generalized symptoms (malaise, fever headache).
- With characteristic maculopapular rash and generalized
lymphadenopathy
- Mucosal ulcers in the mouth
- Warty lesions on perianal region & vulvae
During primary & secondary stages, the patient is
infectious.
Latent stage
Features of secondary syphilis resolve and patient appear
clinically well (controlled by immunologic factors) but
still have syphilis infection
late complication of syphilis
\
No complication
Late syphilis stage
A- Tertiary Syphilis: 3-30 years after infection involve:
- Skin
- Mucous membranes of upper respiratory tract
- Bones
- Joints
Here the lesions are called "gumma" consist of granulomatous
tissue
(while the lesions in primary stage are called hard chancre &
consist acute inflammation).
B- Quaternary syphilis: 5-30 year after inf. Involve:
- Cardiovascular system
- Central nervous system
Congenital syphilis
Pregnant syphilitic woman can transmit Treponema pallidum to
the fetus through placenta & the fetus either.
- Die
- Still born
- Born live with congenital syphilitic symptom
Keratitis
Huchinson's teeth
CNS anomalies
Lab diagnosis of syphilis
A. Specimens:
1. Tissue fluid from the lesions
demonstrate the
spirochete (T.pullidum)
2. Blood serum
for serology tests
B. Darkfield examination
A drop of lesion exudates
examined under durkfield
microscope for the characteristic motility.
C. Immunofluorescerce
A drop of lesion exudates
stained with fluorescein
labeled antitreponeme serum
examined under
immunofluorescence
microscope
fluorescent
spirochetes.
D. Serological tests for syphilis (STS)
1. Non treponemal antigen test
The Ag used
Cardiolipin
The Ab in patient serum
Reagin (Ab-like substance)
a. Flocculation tests (clumping):
- VDRL (venereal Disease Research Laboratories)
- RPR (Rapid Plasma Reagin)
During treatment of the disease cardiolipin fall
these
tests appear negative
so they are useful for monitoring
the treatment.
b. Complement fixation tests (CFT)
- Wasserman test
- Kolmer test
Non treponemal Ag tests may show False-positive results,
because regain may appear in patients serum due to many
other infections (e.g.: malaria, leprosy, autoimmune
disease, viral & bacterial pneumonia)
2. Treponemal Antibody tests
a. Fluorescent treponemal antibody (FTA ABS):
Is indirect immunofluorescent test (killed treponema +
patient serum (Ab) + fluorescene labeled antihuman
gamma globulin
fluorescent treponema)
- Has high sensitivity & specificity
- First test become positive at early syphilis
- Remain +ve many years after infection
- Not used to judge treatment
b. Treponema pallidum hemagglutination (TPHA):
Treponema + RBCs + patient serum (Ab)
Agglutination.
- This test is similar to (FTA ABS) but appear later in
infection.
c. Treponema pullidum immobilization test (TPI):
Live motile treponema (seen under dark field
microscopy) + patient's serum (Ab) + complement
treponema stop moving (immobile)
- This test not used because the live treponema is dangerous.
Immunity
Infected person do not get super infection but treated cases
becomes again susceptible to infection (No immunity).
Treatment
Penicillin is the treatment of choice, but the rate of killing is
slow because of metabolic inactivity & slow multiplication.
Control:
1. Prompt & adequate treatment
2. Follow up the source of infection
3. Safe sex
It is important to consider possibility of syphilis when
any one of the sexually transmitted diseases has been
found (G.C, Chlamydia) Since they transmit in the same
way.
Diseases related to syphilis
Caused by treponemes closely related to T. pallidum:
1. Bejel [endemic syphilis)
2. Yaws: endemic in children and transmitted by contant.
3. Pinta: endemic in dark skinned races.
Borrelia recurrentis
Causing Relapsing Fever
Epidemic Endemic
Transmitted by body louse transmitted by Ticks
Organism:
- Irregular spirals
- Flexible & motile
- Can be stained by bacteriological stains and blood stains
(Giemsa).
Culture:
- In fluid media containing blood or serum
- And in chick embryos
- Borrelia recurrentis can survive several months at 4
o
C in
infected blood
- Antigenic variations occurs in the course of infection.
Pathology & pathogenesis
- Incubation period 3-10 days
- Chills & abrupt rise in temperature (3-5 days) (i.e. B. recur
abound patients blood)
- Decline in fever (4-10 days)
- Second attacks of fever
- Decline
(3-10 times)
This is due to the antigenic variation so the body produce
antibodies against that variant at each attacks
then the
organism produce other variant.
Fatal cases of relapsing fever show spirochetes in great
numbers in spleen, liver, kidneys & GIT.
Lab diagnosis
- Specimen: Blood obtained during rise in fever
- Smears: Thick and Thin blood smears stained with
Giemsa stain shows the spirochetes
- Serology: CFT
Leptospirae
- Cause leptospirosis
Organism:
- Tightly coiled thin flexible spirochetes
- One end is bent forming a hook
- With rotation motion and no flagella
- Very fine so not stained but by silver impregnation.
Culture
Aerobic culture on protein rich semisolid media.
Pathogenesis
After 1-2 weeks of ingestion of contaminated water or found
febrile onset (spirochetes in blood)
infect liver & kidney
Jaundice
improvement
second phase of infection (IgM
antibody titer increase)
(aseptic meningitis).
- The picture varies in different species
Lab diagnosis
Specimen is blood for:
Dark field microscopy
Thick smear stained with Giemsa
Culture
Serology (agglutination)
Spirochetes of the mouth and mucous
membranes
Occur in normal mouth and on normal genitalia.
They are anaerobic harmless saprophytes.
At injury to mucous membranes ;nutritional deficiency or herpes
simplex infection these normal spirochetes together with
anaerobic
fusiform
bacilli
will
cause
ulcerative
gingivostomatitis (trench mouth) cause ulcerative
tonsillitis called Vincent's angina