Spirochetes

Published on 18/02/2015 by admin

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Last modified 18/02/2015

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Chapter 15

Spirochetes

I Shared Spirochetal Features

A Genera

B Morphology

C Clinical

• Many spirochetal diseases follow a similar clinical course, commonly lasting from months to years if not treated, and induce tissue-damaging immune responses (Box 15-1).

BOX 15-1   Spirochetal Diseases

The diseases caused by various spirochetes exhibit a similar clinical course. The first stage commonly entails the development of a characteristic primary lesion at the site of exposure. The organisms then disseminate via the blood, often causing flu-like manifestations. The disease then remits for a brief period before second-stage signs and symptoms appear. Some diseases exhibit a third stage, which may commence after a prolonged latency period. In most spirochetal diseases, the spirochetes persist in patients for long periods. Common spirochetal diseases and their causative agents include the following:

II Treponema Species

• The pathogenic treponemes (T. pallidum, T. pertenue, and T. carateum) cannot be distinguished morphologically or serologically, but they exhibit distinctive clinical manifestations and epidemiology.

A Shared treponemal properties

1. Treponemes are shorter than Borreliae and possess three axial filaments.

2. Anaerobic (or microaerophilic) organisms that cannot be grown in the laboratory

3. Visualization

4. Serologic tests (Box 15-2)

BOX 15-2   Serologic Tests for Treponema Pallidum and Other Treponemes

VDRL and RPR (nontreponemal tests) measure antibody that reacts with beef cardiolipin. This nonspecific anticardiolipin antibody is induced in response to tissue damage resulting from treponemal infection. These rapid, relatively inexpensive tests are useful screens for syphilis and for monitoring the effectiveness of therapy.

FTA-ABS and MHA-TP (treponemal tests) are specific for antitreponemal antibody but are more expensive than nontreponemal tests and are commonly used to confirm infection. These tests give positive results sooner after infection and remain positive longer (generally for the remaining life of the individual) than nontreponemal tests.

Both types of tests give false-positive reactions in patients with various conditions, including the following:

Treponemal tests (FTA-ABS) measure antigen; nontreponemal tests (VDRL, RPR) measure released lipid and yield false-positive results.

5. Pathogenesis

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