SYPHILIS

What bad can a spiral as thin as 0.1 microns do to a human being?

Yes. This post is going to inform you about the organism TREPONEMA that causes a very well known venereal disease- SYPHILIS.

SYPHILIS

THE DISEASE, MICROBIOLOGY AND MANAGEMENT

Syphilis is a disease of man and few related mammals like monkeys, chimpanzees and rabbits.

This is caused by a spiral shaped bacteria called Treponema pallidum about which we will be discussing shortly. This can be acquired by venereal and non venereal route.

VENEREAL SYPHILIS- As the name suggests, this form of syphilis is caused by sexual contact. The treponeme enters the body through minute skin abrasions or on coming in contact with mucosa.

Infectivity to a partner is maximum in the first 2 years (primary, secondary and early latent periods). As few as 60 bacteria are capable of causing the disease. Once they enter the host, they multiply at the site of entry and disease manifests after about 10-90 days (avg. 1 month). The disease course is divided into the following stages based on the type of lesion;

CONGENITAL SYPHILIS- Infection is transmitted transplacentally and manifests only after the fourth month of gestation, which suggests that pathogenesis requires an immune response. This can be prevented by adequately treating the mother.

DIAGNOSIS

Involves the demonstration of Treponema under the microscope and of antibodies in patient’s serum or CSF sample.

Specimen- is collected with great care from the skin lesions; mild pressure is applied and the     exudate is collected. In cases of neurological manifestations, CSF is collected.

Microscopy- Applicable in cases of early syphilis (primary, secondary and early latent periods). The organisms are not visible under light microscopy as they are very slender.

·       Dark ground microscopy is useful but has low sensitivity.

·       Direct fluorescent antibody tests for Treponema pallidum (DFAT- TP) are better and safer. The use of specific monoclonal antibodies in the test has made it more reliable.

·       Silver impregnation smears–Fontana’s method and Levaditi’s method are commonly used.

Figure 1 DARK GROUND MICROSCOPY

Serology- A large number of serological tests has been described. They can divided into two categories:

Non Treponemal Tests (NTTs) or Standard tests: The antigen used is purified lipid extract of beef heart with added lecithin and cholesterol. To this, inactive serum is added and clumping/ flocculation is observed. This is used by the VDRL (Venereal Disease Research Laboratory).Other NTTs are-

·       Rapid Plasma Reagin (RPR) test

·       Wasserman test

·       Kahn test

BIOLOGICAL FALSE POSITIVES are seen approximately 1% of total population. This is the major drawback of non specific / non treponemal tests. 

These tests are used for screening.

Specific Treponemal Tests (TTs): Antigen used is a specific treponemal antigen which is obtained from the virulent Nichole’s strain. These tests are used for confirmation.

·       Treponema Pallidum Immobilisation (TPI) –If antibodies are present in the serum sample, the treponemes are rendered immobile when viewed under dark ground microscope.

·       Fluorescent Treponemal Antibody (FTA)- It is an indirect immunofluorescence test. The currently used modification of this test is FTA- absorption (FTA-Abs).

·       Treponema Pallidum Hemagglutination Assay (TPHA)

·       Treponema Pallidum Particle Agglutination (TPPA)

·       Enzyme Immuno Assay (EIA)

 

A negative TPHA virtually excludes the diagnosis of syphilis except in few early cases. Detection of specific IgM antibodies is also helpful as they are the initial type of antibody to appear. The antibodies cease after elimination of the disease, persistence indicates continual active disease and need for treatment.

Figure 2 DIAGNOSIS

PROPHYLAXIS AND TREATMENT

As transmission is by direct contact, it is possible to prevent disease by avoiding sexual contact with affected individual, using physical barriers, applying antiseptics like potassium permanganate. Health care workers should use protective equipments before handling samples. No vaccine is available as of now.

Preferred treatment options-

Benzathine Penicillin G is the drug of choice for both early and late syphilis.

·       Early syphilis- 2.4 million units of Benzathine penicillin G is adequate.

·       Late syphilis- same amount repeated weekly for three weeks.

In case of penicillin allergy, Doxycycline is preferred.

For neurosyphilis,- Ceftriaxone is particularly effective.

During pregnancy -only Benzathine penicillin is used, and if the patient is allergic, de-sensitisation of allergy is done.