Table of Contents
Classification
Class- Spirochaetes
Order- Spirochaetales
Family- Spirochaetaceae
Genus- Treponema
Species- Treponema pallidum
Image Source: Russell Publishing Limited.
Morphology of Treponema pallidum
- Treponemes are thin, delicate, helically coiled, corkscrew-shaped organisms.
- They are microaerophilic and actively motile.
- They are measures about 10 to 14 micrometers long and 0.1 to 0.2 micrometer wide.
- They have 8-24 sharp and angular spirals, at regular intervals of about 1 micrometer.
Cultural Characteristics of Treponema pallidum
- This organism has not been successfully cultured in vitro.
- Preservation media: 18-21 days.
- Dieterle stain: Can be used to visualize T. pallidum.
Biochemical Characteristics of Treponema pallidum
- Treponema is composed of approximately 70% proteins, 20% lipids, and 5% carbohydrates.
- This lipid content is relatively high.
- The lipid composition of T. pallidum is complex, consisting of several phospholipids, including cardiolipin and poorly characterized glycolipid.
Antigenic Structure
Treponema induces at least 3 types of antibodies.
a) Reagin antibodies: react in standard or non-specific test for syphilis.
b) Group antigen: found in pathogenic and non-pathogenic treponemes.
c) Polysaccharide antigen: species-specific, demonstrated by specific T. pallidum tests.
Virulence Factors
- Following attachment, a cell-bound toxin results in lysis of the cells.
- Intact cell layers with tight junctions support bacterial attachment but hyaluronidase treatment of cells decreases attachment.
Resistance
- It is a fastidious organism that exhibits narrow optical ranges of pH 7.2 to 7.4 and temperature 30 to 37°C.
- It is rapidly inactivated by mild heat (41-42°C in one hour), cold ( 0-4°C in 1-3 days), drying, and most disinfectants.
Pathogenesis
- It caused Syphilis disease.
- Humans are the only natural host for T. pallidum and infection occurs through sexual contact.
- The organism penetrates the mucous membrane or enters minuscule breaks in the skin.
- In the women, the initial lesion is usually on the labia, the walls of the vagina, or the cervix.
- In men, it is on the shaft or glans of the penis.
- A chancre (a small hard painless nodule at the site of entry of pathogen) also may occur on lips, tongue, tonsils, anus, or other skin areas.
- Perivascular inflammation: This typically consists of a proliferation of adventitial cells; perivascular cuffing with lymphocytes, monocytes, and plasma cells; and swelling and proliferation of endothelial cells.
Clinical Manifestation of Treponema pallidum
1. Primary syphilis:-
Primary lesion or “Chancre” develops at the site of inoculation after 18-21 days.
Chancre:
• Progresses from macule to papule to ulcer.
• Typically painless, indurated, and has a clean base.
• Highly infectious
• Cartilage like consistency
• Heals spontaneously within 1 to 6 weeks.
• 25% present with multiple lesions.
• Chancre also can develop on the cervix, tongue, lips, or other parts of the body.
2. Secondary syphilis:-
• Secondary lesions occur 3 to 6 weeks after the primary chancre appears.
• may persist for weeks to months.
• primary and secondary stages may overlap.
• Mucocutaneous lesions are most common.
• SYMPTOMS: Fever, Swollen lymph glands, sore throat, patchy hair loss, weight loss, headache, muscle aches, fatigue.
3. Latent syphilis:-
- The host suppresses infection – no lesions are clinically seen.
- The only evidence is a positive serologic test.
- May occur between:
a) primary & secondary stages
b) secondary relapses
c) after the secondary stage.
# Categories:
a) Early latent – <1 year duration
b) Late latent – > equal to 1 year duration.
A. Late syphilis
• Approximately 30% of untreated patients progress to the tertiary stage within 1 to 20 years.
• Rare because of the widespread availability and use of antibiotics.
• SYMPTOMS:
I. Cardiovascular syphilis
II. Neurosyphilis
B. Congenital syphilis
• Occurs when T. pallidum is transmitted from a pregnant woman to her fetus.
• May leads to; stillbirth and neonatal death.
References and Sources
- 14% – https://www.slideshare.net/daulatramdhaked/treponema-pallidum-tutorial-1712014
- 14% – https://www.ncbi.nlm.nih.gov/books/NBK7716/
- 8% – https://www.slideshare.net/Prbn/treponema-pallidum-49670354
- 4% – https://www.slideshare.net/AmirRajaey/treponema-pallidum-74385505
- 3% – https://www.powershow.com/view/104cc-ZTdmY/Syphilis_powerpoint_ppt_presentation?varnishcache=1
- 2% – https://www.uptodate.com/contents/congenital-syphilis-clinical-features-and-diagnosis/print#!
- 1% – https://www.cdc.gov/std/syphilis/stdfact-syphilis-detailed.htm
- 1% – https://medical-dictionary.thefreedictionary.com/chancre
- 1% – https://en.m.wikipedia.org/wiki/Spirochaete