Syphilis - causative agent - morphology - epidemiology - pathogenesis - symptoms - diagnosis - prophylaxis - treatment

1. BACTERIAL DISEASE
SYPHILIS
WATHMI GUNAWARDANA
AMANDA FONSEKA

2. Introduction
• Syphilis is a sexually transmitted infection caused by the bacterium
Treponema pallidum.
• It was first isolated from syphilitic lesion in 1905.
• Syphilis is most commonly spread through sexual activity. It may also be
transmitted from mother to baby during pregnancy or at birth, resulting
in congenital syphilis.
• Rarely syphilis has been acquired by transfussion of infected fresh human
blood.
• Virulence factors - The T. pallidum genome sequence does not reveal any
obvious classical virulence factors that could account for syphilis signs and
symptoms. It’s virulence factors are still unknown

3. Classification
• Treponema pallidum
Domain:Bacteria
Phylum:Spirochaetes
Order:Spirochaetales
Family:Spirochaetacea
Genus:Treponema
Species:T. pallidum

5. Pathogen morphology
• Gram negative bacteria which is spiral in shape.
• Very small in size with a length that ranges from 6 to 20 micrometer.
• Endo flagella are found in the periplasmic space between its two
membranes which give motility to them.
• Show rotatory corkscrew like movement.
• Too thin to be seen by gram stain. Therefore stained by silver
impregnation method.

6. Epidemiology
https://www.nature.com/articles/nrdp201773
The World Health Organization
estimates that 12 million new
cases of syphilis occur each
year.
50% of stillbirths are caused by
syphilis in Tanzania.

7. Transmission
• Syphilis is transmitted primarily by sexual contact or
during pregnancy from a mother to her fetus; the spirochete is able to
pass through intact mucous membranes or compromised skin.
• It is thus transmissible by kissing near a lesion, as well as oral, vaginal,
and anal sex.
• Approximately 30% to 60% of those exposed to primary or secondary
syphilis will get the disease. Most (60%) of new cases in the United
States occur in men who have sex with men.

8. Primary and Secondary Syphilis — Distribution of Cases by Sex and Sexual Behavior, 2016
https://www.cdc.gov/std/stats16/figures/36.htm

9. Low risk:
• Syphilis can be transmitted by blood products, but the risk is low due
to blood testing in many countries. The risk of transmission
from sharing needles appears limited.
• It is not generally possible to contract syphilis through toilet seats,
daily activities, hot tubs, or sharing eating utensils or clothing.
• This is mainly because the bacteria die very quickly outside of the
body, making transmission by objects extremely difficult.

10. Resistance
• Fastidious organism that exhibits narrow optimal ranges of
• pH 7.2 to 7.4
• Temperature 30 t 37ᵒC.
• It is rapidly inactivated by mild heat (41-42ᵒC in one hour), cold (0-4ᵒC
in 1-3 days), drying and most disinfectants.
• Stored frozen at -70ᵒC in 10% glycerol or in liquid nitrogen (-130ᵒC) for
10- 15 years.

12. Symptoms of syphilis

14. Primary Stage
• A single sore (chancre) or multiple sores around the area where the
bacteria entered the body.(genitals, tongue, and lips most commonly)
• Sores are usually (but not always) firm, round, and painless.
• The sore usually lasts 3 to 6 weeks and heals regardless of whether or
not you receive treatment.

15. Secondary Stage
• Development of lesions in the mucous membranes of
mouth, anus, vagina and penis.
• A non-itchy, painless reddish brown rash spreads through
the whole body (including palms and soles) after primary
sore is healed.
• Other symptoms you may have can include fever, swollen
lymph glands, sore throat, patchy hair loss, headaches,
weight loss, muscle aches, and fatigue (feeling very tired).

17. Latent Stage
No clinical manifestations
Tertiary stage (Neurosyphilis and Ocular Syphilis)
Symptoms of neurosyphilis include
• severe headache;
• difficulty coordinating muscle movements;
• paralysis (not able to move certain parts of your body);
• numbness; and
• dementia (mental disorder).
Symptoms of ocular syphilis include
• changes in your vision and even blindness.

18. Laboratory diagnostic test
for syphilis
Treponemal testsNontreponemal tests
Direct tests Serological tests

19. 1) Dark-field microscopy
Direct detection methods
Exudes and fluids from lesions
are isolated
Wet mount prepared
Observed under dark field
microscopy

20. Advantages
• Most simplest and reliable methods to diagnose syphilis if lesions are
present.
Disadvantages
• Identification is based on the motility of the spirochetes observed
therefore specimen needs to be visualized shortly after obtaining.
• Low sensitivity as visualization maybe impaired by the amount of
specimen, presence of refractive elements in specimen, thickness of
glass slide

21. 2) Direct Fluorescent Antibody
Test (DFAT)
Exudes and fluids from lesions are
isolated
Fluorescence labelled(isothicyanate)
antibody targeting antigen in T. pallidum
added
Observed under fluorescent microscopy

22. Advantages
• Easier to perform than dark field microscopy.
• Organisms do not need to be motile as identification is based on
presence of antigen.
Disadvantages
• Non-specific - Cannot distinguish between T pallidum and other
pathogenic treponemes causing yaws, endemic syphilis and pinta.

23. 3) DNA amplification methods (PCR and RT-PCR)
• A number of PCR-based methods have been developed for the
detection of T pallidum in clinical specimens.
• Not standardized but highly sensitive - able to detect as low as one to
10 organisms per specimen with high specificity.
• PCR is a test of choice for congenital syphilis, neurosyphilis and early
primary syphilis when traditional tests have limited sensitivity.
• This method could be used to monitor treatment.
• There is also potential to use it to differentiate new infections from old
infections.
• No commercially available PCR-based test kits.

24. A nontreponemal test (NTT) is a blood test for diagnosis of infection
with syphilis. Nontreponemal tests are an indirect method in that
they detect biomarkers that are released during cellular damage that
occurs from the syphilis spirochete.
Syphilitic infection leads to the production of nonspecific antibodies
that react to cardiolipin.
Centers for Disease Control and Prevention (CDC)-approved standard
tests include the Venereal Disease Research Laboratory (VDRL) slide
test, the rapid plasma reagin (RPR) card test, the unheated serum
reagin (USR) test and the toluidine red unheated serum test
Serological testing – Nontreponemal tests

25. Advantages
• Nontreponemal tests are rapid, simple and inexpensive. They are
the only tests recommended to monitor the course of disease
during and after treatment.
Disadvantages
• Reduced sensitivity in primary syphilis and late latent syphilis.
• The disproportionate antibody-to-antigen ratio results false
negatives. Specimens will give a clearly positive reaction when
diluted and retested, a process that brings the antibody-to-antigen
ratio within the optimal range.​

26. Venereal Disease Research
Laboratory (VDRL) test
Inactivated(heated) serum is place in a
cavity slide.
Cardiolipin antigen is then added with the
help of a syringe to the well and rotated at
180 rpm for 4minutes
The slide is then viewed under low power
objective of a microscope for flocculation.

27. Serological testing – Treponemal tests
• Treponemal tests are used to identify specific antibodies used mainly
as confirmatory tests to verify reactivity in nontreponemal tests.
• In populations of low disease prevalence, treponemal tests can be used
for screening.
• Examples of treponemal tests:
• Rapid test or enzyme immunoassay (EIA) format
• Treponema pallidum particle agglutination assay (TP-PA)
• Fluorescent treponemal antibody absorption test (FTA-ABT) and
fluorescent treponemal antibody absorption double staining tests

28. Enzyme immunoassay (EIA)
Specimen poured into microtiter wells coated
with T. pallidum antigens and incubated
Unbound specimen washed off
Secondary monoclonal antibody tagged with
horse radish peroxidase is added
Unbound mAbs are washed off, peroxidase is
added and colour change is observed

29. Culture characteristics of T.
pallidum

30. • T. pallidum cannot be cultured in culture medium.
• Animal models are needed to study syphilis. Although mice and
monkeys can be used, rabbits are the animal model almost
exclusively studied in the lab.
• Rabbits are used because unlike monkeys they are inexpensive and
unlike mice, rabbits develop the signs and symptoms of human
primary and secondary syphilis.

31. Prevention of syphilis

32. • Abstaining from sex with infected persons.
• Proper usage of latex condoms – the condom
requires to cover the syphilis sores in order to
prevent transmission.
• Congenital syphilis can be prevented by
screening mothers using PCR and treating
them.

33. Treatment of syphilis

34. What is the treatment for syphilis?
Benzathine penicillin G (2.4 million units administered intramuscularly)
• Syphilis is easy to cure in its early stages.
• Primary, secondary or early latent syphilis- A single intramuscular
injection of long acting Benzathine penicillin G.
• Late latent syphilis or latent syphilis of unknown duration - Three doses
of long acting Benzathine penicillin G at weekly intervals is
recommended. Treatment will kill the syphilis bacterium and prevent
further damage, but it will not repair damage already done.
• Non-pregnant patients who are allergic to penicillin may include
doxycycline, tetracycline, and for neurosyphilis, ceftriaxone.

35. References
1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2095002/
2. https://www.cdc.gov/std/syphilis/treatment.htm
3. https://microbewiki.kenyon.edu/index.php/Treponema_pallidum
4. https://en.wikipedia.org/wiki/Syphilis#Epidemiology
5. https://www.nature.com/articles/nrdp201773