Question

Explain the mechanisms the following organisms affect their host tissues by causing diseases.

5 members of the genus Treponemes

Borrelia

5 members of the vibrio species

Ritckettsiales

Coexiella and Bartonella

Chlamydias and mycoplasmas

Organisms that causes dental diseases

Answer 1

The family spirochaetaceae has three major genera:Treponema, Borrelia, and Leptospira​​​​​​. These three genera infect the nervous system producing meningoencephalitis, infectious myelitis, meningoradiculoneuritis and peripheral nerve inflammation.

The spirochete borrelia burgdorferi was identified as the cause of Lyme disease. B. Burgdorferi can spread throughout the body during the course of the disease, and has been found in the skin, heart, joints, peripheral nervous system and central nervous system. B. Burgdorferi is injected into the skin by the bite of an infected Ixodes tick. Tick saliva, which accompanies the spirochete into the skin during the feeding process, contains substances that disrupt the immune response at the site of the bite. The spirochete multiply and migrate outward within the dermis. The host inflammatory response to the bacteria in the skin causes the characteristic circular lesion.

Days to weeks following the tick bite, the spirochete spread through the bloodstream to joints, heart and distant skin sites, where there presence give rise to variety of symptoms of the disseminated disease.

In the brain B. Burgdorferi may induce astrocytes to undergo astrogliosis which may contribute to neuro dysfunction. The spirochete may also induce host cells to secrete quinolinic acid, which stimulates NMDA receptors on nerve cells, which may account for fatigue and malaise observed with lyme encephalopathy.  

Mechanism of action of vibrio species:

Vibrio cholerae secrets cholera toxin, a protein that causes diffuse watery diarrohea. The v. Cholerae particle in the intestinal lumen then uses fimbriae to attach to the intestinal mucosa,not invading the mucosa. After that it secretes toxins that causes symptoms.