Introduction
Syphilis is a sexually transmitted illness that primarily affects the skin and mucous membranes of the external genitalia. It is caused by a bacterium called Treponema pallidum, which belongs to the class of bacteria known as spirochetes. Despite having a different cell envelope than other gram-negative bacteria, T. pallidum is classified as a gram-negative bacterium. This blog will delve into the various aspects of syphilis, including its transmission, stages, and treatment options.
The Nature of Treponema Pallidum
Treponema pallidum is an obligatory parasite, meaning it cannot survive outside of a live organism. It is a type of bacterium that specifically infects humans and is transmitted primarily through sexual contact. T. pallidum is a spirochete, characterized by its long, thin shape and endoflagella, which are spiral-shaped protein filaments that aid in the bacterium's mobility.
Similar to a drill digging into a piece of wood, the twisting motion of the endoflagella allows T. pallidum to navigate through various tissues in the body. These spirochetes are responsible for the spiral shape of T. pallidum, giving it a resemblance to curly fries.
Transmission of Syphilis
Syphilis can be transmitted through two main methods: acquired syphilis and congenital syphilis.
Acquired Syphilis
Acquired syphilis occurs when an individual contracts the infection through sexual contact or by coming into contact with an infected person's skin lesion. Sexual intercourse, including oral, anal, and vaginal sex, as well as microscopic wounds or tears in the skin or mucous membranes, can facilitate the entry of T. pallidum into the body.
Additionally, using contaminated needles or close contact with an infected person's skin lesion can also lead to the transmission of acquired syphilis. The primary symptom of acquired syphilis is the development of hard chancres, which are painless ulcers that typically appear on the external genitalia.
Congenital Syphilis
Congenital syphilis occurs when a pregnant woman with syphilis transmits the infection to her unborn child. The bacterium can infect the fetus either within the uterus or during birth as the baby passes through the birth canal. Congenital syphilis can have various effects on the newborn, ranging from a maculopapular rash on the palms and soles of the feet to more severe complications such as damage to the liver, spleen, or eyes.
Stages of Syphilis
Primary Syphilis
Primary syphilis is the first stage of the infection and typically occurs one to three weeks after T. pallidum attaches itself to the skin or mucous membrane. The hallmark symptom of primary syphilis is the development of hard chancres at the site of infection. These chancres are painless and have elevated edges. They are often coated with a fluid containing spirochetes. The main chancre usually appears on the external genitalia in individuals who acquire syphilis through sexual contact.
However, it can also manifest on other body parts in individuals who acquire syphilis through personal contact with a lesion or other methods. Syphilitic chancres resolve on their own within a few months, and during this stage, the infection can progress to the next phase.
Secondary Syphilis
Secondary syphilis occurs approximately six to twelve weeks after the initial infection. During this stage, T. pallidum enters the bloodstream and spreads throughout the body. Generalized lymphadenopathy, characterized by enlarged lymph nodes all over the body, is a common feature of secondary syphilis.
Another characteristic symptom is the development of a maculopapular rash. This rash is non-itchy and starts on the trunk before spreading to the arms, legs, palms, soles, genitalia, and other mucous membranes. The rash can be accompanied by other skin manifestations, such as papulosquamous rashes or pustular lesions. Condyloma lata, smooth and painless lesions resembling warts, can also appear in moist areas like the armpits, genitalia, and surrounding anal region.
Secondary syphilis is the most contagious stage of the infection, as spirochetes are abundant in the lesions and rashes that can appear anywhere on the body. Without treatment, secondary syphilis rashes typically disappear within a few weeks to months.
Latent Syphilis
Latent syphilis is a phase characterized by a lack of symptoms. During this period, spirochetes reside mainly in the tiny capillaries of various organs and tissues. There are two phases of latent syphilis: early and late.
Early latent syphilis occurs within a year of infection and may still present with symptoms similar to secondary syphilis. The spirochetes can re-enter the bloodstream, causing a recurrence of secondary syphilis symptoms. In contrast, late latent syphilis occurs after one year and is usually asymptomatic. Although there may be few spirochetes present in the capillaries of tissues and organs, the immune system mounts a strong reaction, resulting in inflammation and damage to cells.
Tertiary Syphilis
Tertiary syphilis is the most severe stage of the infection and occurs when the immune response to T. pallidum causes extensive tissue damage. A type IV hypersensitivity reaction, driven by T cells, leads to the recruitment of macrophages and other immune cells. This immune response can result in systemic symptoms such as fever, as well as localized signs like redness, warmth, and swelling.
Tertiary syphilis can affect various organs, including the heart, blood vessels, brain, spinal cord, liver, joints, and testes. Cardiovascular syphilis is characterized by inflammation of the small arterioles called vasa vasorum, leading to inflammation of the aorta (aortitis) and the potential development of aortic aneurysms. Neurosyphilis can result in conditions such as tabes dorsalis, which affects the posterior section of the spinal cord, and general paresis, which primarily affects the legs and can cause sensory loss and paralysis.
Diagnosis and Treatment
Diagnosis
The diagnosis of syphilis involves a combination of clinical evaluation and laboratory testing. Dark-field microscopy can be used to detect spirochetes in the fluid from the chancres. Serological assays, such as the Venereal Disease Research Laboratory test (VDRL) and the Rapid plasma reagin test (RPR), are used to detect antibodies against T. pallidum antigens. These tests are not specific to syphilis and can also detect antibodies produced in response to other conditions.
Treponemal tests, including fluorescent treponemal antibody absorbed (FTA-ABS) and T. pallidum-particle agglutination (TPPA), are used to confirm the diagnosis by identifying anti-T. pallidum antibodies.
Treatment
The primary treatment for syphilis is penicillin. Doxycycline may also be used in certain circumstances. It is important to be aware of the possibility of a Jarisch-Herxheimer response when administering penicillin. This response occurs when the spirochetes rupture and release antigens, leading to an overreaction of the immune system and resulting in symptoms such as fever, sweating, and muscle and joint pains.
For the diagnosis of congenital syphilis, the test results of both the mother and the child are compared. Treatment options depend on the severity of the infection and may include intravenous penicillin therapy.
Conclusion
Syphilis, caused by the bacterium Treponema pallidum, is a sexually transmitted infection that affects various organs and can have serious consequences if left untreated. Understanding the stages of syphilis, its modes of transmission, and the importance of timely diagnosis and treatment is crucial in preventing further spread of the infection and managing its complications.
