Syphilis: Treponema pallidum

infection

• Causative agent: spirochete Treponema pallidum.

• Extremely fastidious, and fragile; sensitive to disinfectant, heat, and drying.

• Treponema pallidum is a chemoheterotrophic, secretes the enzyme hyaluronidase.

• Transmission: sexual, blood transfusion, transplacental.

Pathogenesis and tissue damage: Stages of syphilis:• Primary stage: after 3 weeks of

incubation.• Secondary stage.• Latent stage.• Tertiary stage (complications).• Congenital.

Primary syphilis:• The bacterium enters the body through a break in the

skin, or by penetrating the mucous membranes of the genitalia.

• Tissue destruction in primary syphilis:o The microbial virulence: Microbial

hyaluronidase destroy the polysaccharide (hyaluronic acid; glycosaminoglycan) that holds host cells together in the extracellular matrix.

o The cellular immune defenses: (Neutrophils, lymphocytes, and macrophage) against replicating Treponema and tissues.

• This results in an ulcer formation (chancer).

N

• After three weeks of inoculation, syphilitic chancre appears on the site of entry (usually the genitalia).

• Chancre is a single, painless, non-itchy skin ulcer with a clean base and sharp borders between 0.3 and 3.0 cm in size.

• Chancre heals spontaneously within 3-6 weeks but the microbe continues to spread via the lymph and blood in asymptomatic period lasting 2- 24 weeks.

N

Secondary Syphilis:Characterized by: • Red-maculopapular rash on almost any

part of the body. • Condylomata lata: Wart like lesions on the

anogenital region. • Hepatitis, glomerulonephritis and

meningitis. • Secondary syphilis resolve within weeks to

months.

moth-eaten alopecia

N

Latent syphilis stage : In two-thirds of individuals who acquire

syphilis. After healing of secondary syphilis, the microbe

enters a latency period that can last 3-30 years. In one-half of this group, tertiary syphilis is

established. Asymptomatic period but serologic tests show

positive results.

N

Tertiary syphilis: Occur three to 15 years after the initial infection.Divided into three different forms: • Gummatous syphilis:

granulomatous lesions in the liver, skin, and bones (15%).

• Neurosyphilis (6.5%): infection of the brain parenchyma and dorsal column of spinal cord.

• Cardiovascular syphilis (10%): Vasculitis and aortic valve insufficiency.

Dilatation of the aorta

Congenital syphilis:The microbe can be transmitted to the fetus from infected mother (transplacentally) after the first ten to fifteen weeks of pregnancy.

Congenital syphilis is associated with:• Intrauterine growth retardation.• Hepatosplenomegaly.• CNS infection: hydrocephalus, optic atrophy, and

seizures.• Mucocutaneous lesions.• lymphadenopathy.

Saber shins Hutchinson teeth

Saddle nose

Diagnosis of Syphilis:Clinical specimens: Exudate (pus), tissue biopsy, and serum specimens.Direct: • Microscopy in microbiology laboratory

and histopathology laboratory.• Culture: animal inoculation.Indirect:• Serology: specific and non specific tests.

In Microbiology Lab:A- Dark field microscopy: Rotary corkscrew-like motility with 90˚ angulation.B- Immunofluorescent microscopy: staining of microbe by anti-treponemal antibodies.In Histopathology Lab:Bright-field microscopy: modified Steiner silver stain.

N

Cultivation of Treponema pallidium:-The bacterium do not grow on conventional culture media.-Animal inoculation can be used for cultivation of microbe.

N

Indirect diagnosis: Serology: • Non treponemal tests (non-specific): Anti cardiolipin antibodies by Venereal Disease Research Laboratory (VDRL) or rapid plasma reagin (RPR) test .• Treponemal test (specific): Detection of anti treponemal antibodies by T. pallidum haemagglutination test (TPHA) or fluorescent treponemal antibodies absorption (FTA-Abs). Treatment:• All species are sensitive to penicillin.• Alternate therapy: tetracycline and erythromycin.

RBCs +treponemal antigens

TPHA FTA-Abs