Primary syphilis is indicated by a single skin lesion known as a hard chancre that can appear on the cervix, penis or anus. It can appear 10 to 90 days after exposure. The hard chancre is typically not painful and so it can go unnoticed and will typically heal. Primary syphilis can go unnoticed because of these symptoms

Primary Syphilis

Secondary syphilis has a rash that is localized around the mouth, vagina or anus. It can begin around the feed and spread to the limbs as well. The rash can be mucus filled or red bumps. This stage is highly contagious. 

Secondary Syphilis

Tertiary syphilis can appear 10 to 20 years after secondary syphilis once it has entered a latent phase. These symptoms can be fatal. Granulomatous lesions or gummas, can develop in mucous membranes, bones and internal organs. They become most deadly if they form in the cardiovascular system or the central nervous system. It can also cause dementia, personality changes, loss of vision, and speech impairment. 

Tertiary syphilis

In order to diagnose syphilis infections, it is important to know the three stages of syphilis infection: 
- Primary syphilis
- Secondary syphilis
- Tertiary syphilis

University of Wisconsin - Madison

*Treponema pallidum* is a gram-negative bacteria that causes the disease syphilis. 

*Treponema pallidum*

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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OpenStax Microbiology Textbook

*Treponema pallidum* s a gram-negative bacteria that has lipoproteins can activate the host immune response. This can cause damage to host tissues and allow the pathogen to evade the host immune system and spread. 

Virulence factors of *Treponema pallidum*

Stages of Syphilis Infection

- nontreponemal serologic test
- treponemal serologic test
- Silver stain microscopy

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