TREPONEMA PALLIDUM

It is the causative agent of syphilis.

MORPHOLOGY:-

Shape:- It is thin, delicate spirochaete with tapering ends having bout 10 regular spirals. 
Size:- 10um long and 0.1 -0.2 um wide.
Nature:- Actively motile, show rotation around the long axis, backward, and forward movement.
Staining:- It doesn't take ordinary bacterial and can't be seen  in the light microscope.

CULTURE:-

Pathogenic treponemas can't be grown  in artificial media but are maintained by subculture in susceptible animals.

ANTIGENIC STRUCTURE:-

Treponemal infection leads to production of at least three types of antibodies. On the basis of which the Treponemal antigen divided into- 

 1. Specific Antigen:- 

 A.Group-specific Antigen:- All pathogenic and non-pathogenic treponemas possesses a common group of antigens.

B. Species-specific Treponemal antigen:- It appears to be polysaccharide in nature and Is present in the Treponemal body.

2. Non Specific Antigen:- 

A non-Specific Antibody appears in the blood of the syphilitic patient.

RESISTANCE:-

  • T. Pallidum is a very delicate organism. It is readily inactivated by drying or by heat (41-42°c in one hour) .
  • It is killed at 0.4°c within 3 days.
  • Store at -70°c in 10% glycerol or in liquid nitrogen, it remain viable for several years.

PATHOGENESIS:-

  • Natural Infection with T. Pallidum occur only in human beings.
  • Veneral syphilis  is acquired by sexual contact.
  • Incubation period 10-90 Days.
STAGES:-
There are three clinical stages of the disease describe are –

I. Primary Syphilis:-

  • The typical lesion of 1° Syphilis is the change which appears at genitals or at extragenital sides in 2-4 weeks after exposure to infection.
  • A hard chancre is painless, relatively avascular, indurated and circumscribed lesions.
  • It is covered by a thick exudate , very rich in spirochetes.
  • The spirochetes spread from the site of entry into the lymph and bloodstream.
  • Antibody tests are positive in 1-3 weeks after the appearance of chancre. 
  • The chancre heals without starring even in the absence of treatment.

II. Secondary Syphilis:-

  • Inadequately treated patients of 1° Syphilis develop MUCOCUTANEOUS LESIONS and painless in 2-3 months after the exposure. 
  • The mucocutaneous lesion may be in the form of a mucus patches on mouth, pharynx, and vagina .
  • Generalize with a skin eruption.
  • Antibody test are always positive as secondary Syphilis is a highly ineffective stage and spirochaetes can be easily demonstrated in the Mucocutaneous lesion.

III. Tertiary Syphilis:-

After a latent period of Appearance of the secondary lesion and tertiary lesions of syphilis appear. The tertiary lesions contain few spirochaetes.
Lesion of tertiary syphilis are much less infective and are of 2 main types- 
 1. Syphilitic Gumma:- It is a solitary localize, a rubbery lesion with Central necrosis seen in the organs line, liver, testes, bone, and brain.

2. Diffuse lesions of tertiary Syphilis:- Mainly seen in the cardiovascular and nervous system. 
A.  Cardiovascular Syphilis mainly involves thoracic aorta. The wall of the aorta is weekend and diluted in syphilitic aortitis and result in an aortic aneurysm incompetence of aortic valve.
B. Neurosyphilis may manifest as:- 
  • Meningovascular Syphilis affecting meninges. 
  • Tabes dorsalis affecting the spinal cord.
  • General paresis affecting the brain. 

3. Congenital Syphilis:- The treponemas can cross the placental barrier. It may develop in the fetus of more than 16 weeks gestation who is exposed to maternal spirochaetaemia.
4. Syphilis acquired nonvenerally:-It may occur in doctors or nurses due to contact with patient lesion during treatment.

LAB DIAGNOSIS:-

DEMONSTRATION OF TREPONEMES:-

  • Dark ground microscopy.
  • Direct fluorescent antibody- staining for T. palladium (apple green fluorescence)
  • Treponemes in tissues.
  • Silver- impregnation method (Levaditi stain).
  • Immunofluorescence staining.

SEROLOGICAL TEST:-

i. Treponemal tests:-
  • FTA, FTA-ABS (using killed T. palladium).
  • TPHA, MHATP (using T. palladium extract).
  • TPI TEST (using live T. palladium).

ii. Non-treponemal tests:-
  • VDRL
  • RPR

VDRL (venereal disease research laboratory):-
It is the most widely used and rapid serological test where a small quantity of Serum os needed.
It can be used to detect antibodies in CSF. It slides Flocculation Test.
The VDRL antigen must be prepared fresh daily.

Method:- 


Take especially prepared slide with depression of 14 mm diameter each.
 ⇓
A serum sample is heated to inactivate after as CSF needs to not be heated.
 ⇓
0.05 ml of inactivated serum (at 56°c for 30 min ) is taken on a slide.
⇓ 
one drop of freshly prepared cardiolipin anti is added.
⇓
The slide is then at 180rev/min for min by VDRL rotator or manually
⇓
slide examine under lower power objective of microscope.
⇓
If the test is positive, it is quantitated by performing the test with serial dilutions.

Result:-

It is reported as - 
  • Reactive:- means positive - the presence of clumps.
  • Weak reactive.
  • Non-reactive -means negative- uniformly distributed Crystals are observed. 

RPR (Rapid Plasma Reagin)test:-

It is almost similar to the VDRL test. Finely divided carbon particles are added to the cardiolipin antigen.

Advantage (over VDRL):-
  • Unheated serum or plasma can be used.
  • A finger prick sample of blood is sufficient.
  • Not require a microscope and can be done in the field.
  • Available commercially as a little.

Disadvantage:- can't be used with CSF.