What is the pathophysiology of one STI What is the etiology of the selected STI What are the clinical manifestations of the selected STI What is the treatment for the selected STI Use at least one scholarly source to support your findings

Sexually Transmitted Infections- Syphilis

Pathophysiology

Prior to the twentieth century, the pathogenesis of syphilis was not established because the causative agent had not been identified yet. However, in 1905, German scientists identified the causative agent as Treponema pallidum (T. pallidum). Accordingly, T. pallidum is a spirochete bacterium that is invisible in light microscopes but can be identified in darkfield microscopy (Tudor et al., 2022). Transmission of Treponema pallidum occurs mainly through sexual contact. Depending on the size of the inoculum, after infection and before clinical manifestation, the bacteria undergo a period of incubation, which could be between nine to ninety days. After infection, the bacteria enter the body through the mucous membrane and disseminate in both the bloodstream and lymphatic system, gaining access to multiple organs. Due to this invasion, a genital skin lesion will be present at the site of infection. Nevertheless, other non-genital signs of infection include lymphadenopathy, tonsils, and skin lesions on the nipples and the oral mucosa (Tudor et al., 2022). This stage is known as the primary stage, and if left untreated, the skin lesions will heal, but the disease proceeds to the secondary stage.

Once in the body, Treponema pallidum mainly seeds in the cardiovascular system and the central nervous system. Subsequently, the bacteria have fibronectin molecules, which they use to attach themselves to the endothelial surfaces of the blood vessels in the various organs of the systems mentioned above (Tudor et al., 2022). Besides, this attachment to blood vessels leads to inflammation of the blood vessels, also referred to as vasculitis. Notably, this vasculitis leads to the proliferation and swelling of blood vessels, which is another sign of primary syphilis. Syphilis has a slow replication rate, which enables the bacteria to evade the immune system. In the secondary stage, hematogenous spread or dissemination of the bacteria occurs, leading to various symptoms: abdomen, trunk, and cutaneous rashes. Further, the secondary stage of syphilis also includes the proliferation and swelling of blood vessels in the dermis, neutrophilic infiltration, epidermal hyperplasia, and infiltration of plasma cells (Tudor et al., 2022). Notably, these lesions can also resolve themselves without treatment, and the infection undergoes a latency phase where only serological tests can be used for diagnosis.

In the tertiary stage of syphilis, there are more severe infections of the bacteria in the body, leading to conditions like neurosyphilis, which is a bacterial infection in the spinal cord or brain (Tudor et al., 2022). Further, infections in the blood vessels, especially in the main arteries and in the heart, lead to aneurysms and dilations. Subsequently, such effects lead to cardiovascular syphilis. Remarkably, Treponema pallidum can infect the various complex systems of the body, like the central nervous system and visual system, at any stage. As a result, neurological symptoms like meningitis and nerve damage, or retinal vasculitis, can occur even a few months after infection.

Etiology

A spirochete bacterium, Treponema pallidum, causes syphilis. The bacterium was identified in the early twentieth century and was not sequenced till 1998 (Carlson, Dabiri, Cribier, & Sell, 2011). The bacterium is spiral with a thick phospholipid layer, making it gram-negative. This bacterium has four subspecies, T. pertenue, T. pallidum endemicum, T. carateum, and T. pallidum pallidum, all of which cause treponemal diseases including, yaws, bejel, pinta, and syphilis accordingly. Subsequently, only T. pallidum causes the sexually transmitted disease, syphilis, while the other bacteria cause infections that do not require sexual contact (Carlson et al., 2011). Notably, this bacterium can only reside in humans, meaning there are no animal reservoirs. The main method of transmission of syphilis is through direct sexual contact, for example, orogenital, anogenital, and vaginal contact. Notably, some rare cases of non-sexual transmission include blood transfusion and skin-to-skin contact. Lastly, congenital syphilis is a condition whereby a mother infects her child during birth, which can occur in vertical transmission.

Clinical Manifestations

Some common signs and symptoms of syphilis are in the genital area, including painless skin lesions, also known as chancres, warts on genitalia, and discharge, particularly in women. These occur in the primary stage of syphilis. In the secondary stage, symptoms are found on the skin, including small bumps, rashes