Treponemas (Syphilis, others)

Subspecies of Treponema pallidum cause Syphilis, Yaws, and Bejel (also known as endemic syphilis). Spirochetes have a spiral, or corkscrew shape. Microaerophilic, which means they require low oxygen concentration. Rely on the host to meet their nutritional requirements, and are very difficult to culture. Very thin cell walls, which renders them invisible with Gram or Giemsa stains. Darkfield microscopy or direct antibody fluorescent antibody tests are used to visualize these bacteria. Diagnosis of treponemal infection is achieved via serology, which typically includes a nontreponemal screening test followed by a treponemal test. Complex, and virulence factors and infectious mechanisms are not entirely understood. Low toxicity Highly invasive – Flagellar motility – Adhere to components of the extracellular matrix The tissue destruction*associated with treponemal infection is thought to be caused by the host inflammatory response: Bacterial release of lipoproteins recruits and activates immune cells, and lesions are characterized by infiltration of lymphocytes, macrophages, plasma cells, and granuloma formation. Treponema evade the immune system - "stealth pathogen" Resists phagocytosis and removal. The bacteria have relatively few surface proteins and undergo antigenic variation, which inhibits recognition and removal by the host immune system. Caused by Treponema pallidum subspecies pallidum. These bacteria have only human reservoirs, and are transmitted via sexual contact, the placenta, or via contaminated blood transfusion. Primary phase is characterized by localized lesions, which manifest approximately 3-6 weeks after initial infection. CD4+ T cells and macrophages predominate in the lesions, which typically present as painless chancres. Regional lymphadenopathy is also common. The chancres are highly infectious, and usually heal spontaneously within a couple of months; this may give the patient a false sense of security. Secondary phase of syphilis is the result of bacterial dissemination, aka, bacteremia. Approximately 6 weeks after infection, CD8+ T cells, which are cytotoxic, predominate. Widespread maculopapular rash and lymphadenopathy with headache and malaise are common. Patients may also have flu-like symptoms, including fever. In some cases, condyloma lata develop; show that these knobby or wart-like lesions grow in skin folds, especially in the genital/anal regions. Some individuals develop mucosal legions, particularly in the oral cavity. Other organ systems may be affected, and patients can present with hepatic, pulmonary, neurologic, and ocular dysfunctions in the secondary phase of syphilis. Secondary syphilis can resolve spontaneously. Latent phase Patients are usually asymptomatic during the latent stage, but relapse is common, and placental transmission is still possible. Tertiary phase Approximately 30% of untreated patients enter the Tertiary phase, which is characterized by complications that arise years, even decades, after initial infection. Cardiovascular and neurological impairment. Cardiovascular dysfunction is typically related to the aorta and coronary arteries. Neurological dysfunction can include meningitis, ocular and cranial nerve impairment, focal deficits, tabes dorsalis (loss of corrdination), paresis, personality changes, and dementia. Many of these neurologic complications are the result of vascular dysfunction and/or demyelination. Gummas, which are benign, rubbery granulomas, can form in most organ systems; they are especially common in the bones and skin, but also form in the viscera and brain. Congenital syphilis occurs when the bacteria cross the placenta and infect the fetus; infection often leads to spontaneous abortion or stillbirth, or, in live births, abnormal growth and development. HIV co-infection Syphilis increases the risk of HIV infection, although the exact mechanism is uncertain. In co-infected patients, it seems that the diseases interact in ways that shape clinical outcomes. For example, co-infection seems to increase the risk of neurological complications. Transmitted via non-sexual contact. Yaws Infection typically found in children in warm tropical areas. Associated with Treponema pallidum subspecies pertenue. Initial lesions are usually on the lower extremities, but, if the infection is untreated, can lead to more widespread destruction of skin and bone. Endemic syphilis, aka, Bejel Typically affects children living in hot, dry areas, such the Southern and Sahel regions of Africa. It is caused by Treponema pallidum subspecies endemicum. Initial lesions often arise in the oral mucosa; untreated infection causes destruction of skin and bones of the face. Pinta Infection more commonly found in adults. It is caused by Treponema carateum. The initial lesion is typically on the extremities; unlike yaws and endemic syphilis, pinta infection only affects the skin. Penicillin is the drug of choice. However, be aware that some patients will experience a Jarish-Herxheimer reaction 4-16 hours after penicillin administration. Once thought to be caused by an allergy, we know think the reaction is caused by the killing of the spirochetes. In most cases, the reaction is nonfatal, and presents with chills, fever, myalgia, and rash. In pregnant women, preterm uterine contractions can occur. Changes in white blood cell count can be telling; look for leukocytosis and lymphopenia. Be aware that more serious organ dysfunction, stroke, or seizures are possible.