1. Properties of Treponema pallidum
@ Treponema is a small, spirochaete
measuring 6-15 x 0.2 μm.
@ It has 6-12 coils.
@ Not seen by light microscopy,
Best seen by dark-field microscopy.
@ It has bending & rotating motility.
@ No culture. May survive in blood.

3. Treponema Antibodies:
@ Non-specific autoantibody (cardiolipin)
@ Specific treponemal antibody.
Non-specific autoantibody (cardiolipin)
@ Produced 2-3 weeks after infection
@ It acts against patient damaged
mitochondria .
@ Detected in serum by cardiolipin Ag.
Hence called cardiolipin antibody

5. @ Cardiolipin antibody is positive in:
Syphilis
Other treponemal conditions
Pregnancy
Autoimmune diseases
Tuberculosis
Leptospirosis
Cancer
Leprosy
Malaria

7. Serological tests for Treponema:
@ Used to diagnose syphilis, yaws, pinta
@ There are two test groups:
* Cardiolipin antigen tests.
* Treponemal antigen tests.
Cardiolipin antigen tests:
@ VDRL test.
@ RPR (rapid plasma reagin) test.
@ Wassermann test: no longer used.

8. VDRL TEST:
@ Only patient serum is used
@ Serum is heated for 30 min. at 56°C
@ Control sera must be included.
@ Cardiolipin antigen is diluted.
@ Result read microscopically from slide
@ Technique is difficult
@ Not very sensitive
@ Few false positive results

11. RPR test:
@ The antigen contains carbon or dye.
@ Result is read by naked eye on a card
@ Both plasma and serum are used.
@ Antigen not diluted or heated
@ Control sera must be included.
@ Technique is easy
@ Good sensitivity
@ Many false positive results

14. Comparison of VDRL AND RPR
Specimen
Only serum used, serum heated
Serum & plasma used, no heating
Antigen
Diluted before use
Not diluted
Reading of results
Microscopically from slide
Macroscopically from card
Technique
Difficult
Easy
Sensitivity
Less sensitive
More sensitive
False positive
Less often
More often

15. Treponemal Antigen Tests:
Three tests:
@ TPHA-T.Pallidum Hemagglutination test
@ FTA-ABS-Fluorescent Treponemal
Antibody-ABSorption test.
Recommended only in reference labs.
@ TPI-Treponema Pallidum Immobilization
test. Costly, difficult to perform, No
longer used for diagnosis of syphilis

18. TPHA:
@ It is cheap, simple, quick to perform,
requires no special equipment.
@ Antigen is derived from Nichol's strain
of T.pallidum.
@ It is coated on sheep RBC.
@ Performed in microtitre plates to save
reagent.
@ Control sera must be included.

21. Interpretation of Serological Tests
Condition
RPR & VDRL
TPHA & FTA-ABS
Primary early syphilis
Positive or negative
Secondary early syphilis
Positive
Late and neurosyphilis
Inactive & treated syphilis
Negative or positive
Congenital syphilis
Active yaws or pinta
Inactive yaws or pinta

22. CSF in neurosyphilis:
@ RPR is not suitable for testing CSF.
@ VDRL usually positive or 45% negative
@ TPHA test is positive.
Serum in neurosyphilis:
@ TPHA is positive.
@ RPR and VDRL are positive or negative