Compare and contrast the pathogenesis of the sexually transmitted diseases chlamydia and syphilis.

Question

What will be an ideal response?

Answer 1

Chlamydia is caused by the intracellular parasite Chlamydia trachomatis. The bacteria are transmitted in a dormant form (elementary bodies), which are phagocytosed by cells of the mucosa and conjunctiva. Within the endosome, the bacteria actively reproduce (reticulate bodies) for about 21 hours, then convert to the dormant form and are released, killing the cell. Thus, chlamydia directly kills host tissues. The lesion at the initial site of infection is usually small and painless, but nearby lymph nodes soon host the infection, become inflamed, and may become draining sores. The lymph node infection, which is known as lymphogranuloma venereum, may be accompanied by fever, chills, muscle pain, and loss of appetite. Untreated infections may involve the urethra and genitalia, causing inflammation, swelling, and tissue damage. Chlamydia remains relatively confined to the vicinity of the site of invasion (i.e., the pelvic area) and may cause enough damage to lead to sterility, but it is not a fatal infection.

Syphilis is caused by the spirochete Treponema pallidum pallidum, which is not an intracellular parasite but readily invades tissue both by producing hyaluronidase and because the flat highly motile bacteria can burrow between cells. The lesion formed at the initial site of infection is a small, painless hard bump that resolves on its own. The bacteria spread from the initial invasion site over the course of weeks to months to establish a systemic infection. As the infection becomes systemic and the immune system responds to the pathogen, the secondary symptoms develop. These include fever and a rash on most of the body, including the palms of the hands and soles of the feet. Eventually, these symptoms fade, and the infection becomes latent. Over the course of years, the infection persists, and the immune response to the infection causes tumor-like tissue damage known as gummas. The bacteria can also invade the central nervous system. Consequently, the tertiary symptomatic stage is characterized by dementia as well as organ failure, especially of the cardiovascular system. Thus, untreated syphilis is eventually fatal.
 Both pathogens are transmitted vertically. Chlamydia is transmitted at the time of birth; as the neonate passes through the vagina the bacteria invade and infect the eyes. Syphilis can cross the placenta and infect the developing fetus. Various body systems are infected and affected resulting in serious congenital defects to stillbirth.