Treponema pallidum

class for mbbs

1. TR EPO N EM A PALLIDUM

2. INTRODUCTION Spirochaetes are elongated, motile, flexible bacteria twisted spirally along the long axis. ( Speira – meaning coil and chaite – meaning hair ). Structurally more complex than other bacteria. Characteristic feature is the presence of varying numbers of endoflagella , which are polar flagella wound along the helical protoplasmic cylinder, and situated between the outer membrane and cell wall. Endoflagella are responsible for motility.

3. Order- Spirochetales Family- (a) Spirochetaceae ;(Genera Treponema & Borrelia ) (b) Leptospiraceae (Genera Leptospira ) Human pathogens are found in the genera Treponema Borrelia Leptospira . Genus Spirochaeta are saprophytes found in water and sewage

4. TREPONEMA Treponemes ( trepos , meaning to turn, and nema , meaning thread) are relatively short slender spirochetes with fine spirals and pointed or rounded ends. Some of them are pathogenic , while others occur as commensals in the mouth, intestines, and genitalia. Pathogenic treponemes are NOT CULTIVIABLE on ordinary media though commensals can be grown in artificial media.

5. TREPONEMA Treponemes cause following diseases in humans : Venereal syphilis caused by T. pallidum . Endemic syphilis caused by T. pallidum (T. endemicum ) Yaws caused by T. pertenue . Pinta caused by T. carateum . They are almost identical in their morphology, antigenic structure and other features but show differences in their clinical features and natural history of the diseases they produce.

6. Treponema pallidum Treponema pallidum , the causative agent of syphilis , was discovered in the chancres and inguinal lymph nodes of syphilitic patients. The name pallidum refers to its pale staining.

7. Treponema pallidum Morphology:- A thin delicate spirochete with tapering ends, about 10µm long (range 4-14µm) and 0.1-0.2µm wide. It has about ten regular spirals, which are sharp and angular, at intervals of about 1µm. It is actively motile , exhibiting rotation around the long axis, backward and forward movement, and flexion of the whole body .(Corkscrew motility)

8. Microscopy In wet films cannot be seen under light microscopy but can be made out by negative staining with India ink. Motility and morphology can be seen under Dark Ground Illumination (DGI) & Phase Contrast Microscope. Gram negative bacilli. Does not take ordinary bacterial stains. Prolonged Giemsa staining – stains light rose red. Stained by silver impregation methods Fontana’s method for films/smears Levaditi’s method for tissue sections .

9. Special Staining Methods Fontana’s and Levaditi’s Methods. 9

10. Cultural characteristics T. pallidum do not grow in artificial culture media. Maintained in motile and virulent form for 10-12 days in complex media under anaerobic conditions. Serial testicular passage in rabbits maintain virulent T.pallidum for many decades eg . Nichol’s strain. Reiter strain ( T.phagedenix ), nonpathogenic treponeme , grows well in thioglycollate medium.

11. Resistance T.pallidum is very a delicate organism. Readily inactivated by drying or heat (41-42 o C in 1hr). Killed in 1-3 days at 0-4 o C . Transfusion syphilis prevented by storing blood for atleast four days in the fridge before transfusion. Remains viable for 10-15 years at -70 o C in 10% glycerol, or in liquid nitrogen (-130 o C). Inactivated by contact with oxygen, distilled water, soap, common antiseptic agents and antibiotics.

12. 12 P a th ology • Penetration: T. pallidum enters the body via skin and mucous membranes through abrasions during sexual contact Also transmitted transplacentally Infective dose is small (60 treponemes being capable of infection). Dissemination: Travels via the lymphatic system to regional lymph nodes and then throughout the body via the blood stream Invasion of the CNS can occur during any stage of syphilis

13. STAGES OF SYPHILIS Primary Secondary Latent • • Early latent Late latent Late or tertiary May involve any organ, but main parts are: Neurosyphilis Cardiovascular syphilis Late benign (gumma)

14. Clinical significance The first symptom of primary syphilis is a hard, painless genital or oral ulcer (chancre) that develops at the site of inoculation. The average period between infection and the appearance of the chancre is about 3 weeks but varies with the number of infecting organisms. This primary lesion heals spontaneously, but the organism continues to spread throughout the body via the lymph and blood. An asymptomatic period ensues, lasting as long as 24 weeks, followed by the secondary stage.

15. Clinical significance The Secondary stage is characterized by the appearance of a red, maculopapular rash on almost any part of the body, including the palms of the hands and soles of the feet. Pale, moist, flat papules seen primarily in the anogenital region, armpits, and mouth. Both primary and secondary lesions teem with T. pallidum and are extremely infectious. The secondary stage may be accompanied by multiorgan involvement, causing hepatitis, meningitis, nephritis.

16. Latent Syphilis 16

17. Tertiary stage Upon healing of the secondary lesions, the disease enters a latent period that can last for many years. In approximately 40 percent of infected individuals, the disease progresses to a tertiary stage. Characterized by degeneration of the nervous system; cardiovascular lesions and granulomatous lesions ( gummas ) in the liver, skin, and bones.

18. Congenital Syphilis • Congenital syphilis usually occurs following vertical transmission of T. pallidum from the infected mother to the fetus in utero, but neonates may also be infected during passage through the infected birth canal at delivery. 18

19. LA B DIAGNOSI S O F SYPHILIS

20. Lab aid essential for – Diagnosis of disease & Assessing cure after treatment Lab diagnosis consists of demonstration of Spirochetes under the microscope ( microscopy ) Antibodies in serum or CSF ( serological test ) Microscopy – done in primary and secondary stages & congenital syphilis Wet films examined under DGI Direct fluorescent antibody test (DFA-TP) Serological tests – mainstay of lab diagnosis. Classified as follows:- Tests for Ab to cardiolipin Ag Tests for Ab to group specific ( treponemal Ag) Tests for Ab to species specific Ag ( T.pallidum )

21. Sample collection For direct examination , exudates from lesions of primary, secondary and early congenital syphilis are the most useful. Clear , serous fluid free of erythrocytes, tissue debris . Serum is the specimen of choice for both nontreponemal and treponemal serological tests. Cerebrospinal fluid (CSF) testing is indicated in congenital and tertiary syphilis and when neurological symptoms are present.

22. Microscopy Can be seen with : Negative staining with Indian Ink. Silver impregnation method Fontana’s stain. Levaditi’s stain . Can also be visualized by using dark-field microscopy . Flourescent microscopy

23. Dark-field microscopy Simplest and most reliable method. Exudates and fluids from lesions are examined as a wet mount. Identification of T pallidum is based on the characteristic morphology and motility. This method is suitable when the lesions are moist. Examination should be done immediately after specimen collection.

24. Non-Specific Treponemal Tests VDRL (lecithins)/ RPR(cardiolipin ) Specific Treponemal Tests. FTA (“gold standard”, subjective) TPPA/TPHA (very sensitive) Immunoblot (good but still early days) Treponemal IgM/IgG EIA (good commercial automated screening test) Treponemal IgM (detected very early) Stay positive therefore useless for diagnosing re-infection or response to therapy.

25. Animal Inoculation Oldest method for detecting infection with T. pallidum. Rabbits were inoculated intra testicularly with T. Pallidum .

26. Nucleic acid amplification methods Highly sensitive Able to detect as low as one to 10 organisms per specimen with high specificity. Used to monitor treatment . Used to differentiate new infections from old infections. May be available only through select laboratories.

27. NON TREPONEMAL TESTS

28. Nontreponemal tests are rapid, simple and inexpensive. They are the only tests recommended to monitor the course of disease during and after treatment. Nontreponemal tests can also serve to detect reinfection. They are also used as screening tests. Limitations – low specificity, low sensitivity in primary and late latent syphilis, false-positive results

29. These include : Complement Fixation Tests Kahn Flocculation test VDRL Unheated Serum Reagin Test (USR) Rapid Plasma Reagin Test (RPR) Toluidine Red Unheated Serum Test (TRUST)

30. COMPLEMENT FIXATION TEST First developed by Wassermann in 1906. In this method, the patient’s serum containing antibodies is made to react with a standardised antigen. Wassermann antigen – extract of liver from newborns who had died of congenital syphilis. Cholesterol and Lecithin were added to increase sensitivity of antigens. Complicated to perform, required many reagents and 24 h to complete