■ Chlamydiae are obligate cell parasites. They go through two stages in their reproductive cycle: the elementary bodies (EB) are optimized to survive outside of host cells. In the form of the initial bodies (IB), the chlamydiae reproduce inside the host cells. The three human pathogen species of chlamydiae are C. psittaci, C. trachomatis, and C. pneumoniae. Tetracyclines and macro-lides are suitable for treatment of all chlamydial infections.

C. psittaci is the cause of psittacosis or ornithosis. This zoonosis is a systemic disease of birds. The pathogens enter human lungs when dust containing chlamydiae is inhaled. After an incubation period of one to three weeks, pneumonia develops that often shows an atypical clinical course.

C. trachomatis is found only in humans. This species causes the following diseases: 1. Trachoma, a chronic follicular keratoconjunctivitis. The pathogens are transmitted by smear infection. 2. Inclusion conjunctivitis in newborn children and swimming-pool conjunctivitis. 3. Nonspecific urogenital infections in both men and women (urethritis, cervicitis, salpingitis, etc.). 4. Lymphogranuloma venereum, a venereal disease observed mainly in countries with warm climates.

C. pneumoniae is responsible for infections of the upper respiratory tract as well as for a mild form of pneumonia. There is current discussion in the literature concerning a possible role of C. pneumoniae in the pathogenesis of atherosclerotic cardiovascular disease. ■

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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