TAILIEUCHUNG - Chapter 169. Chlamydial Infections

Three chlamydial species cause human infections: Chlamydia trachomatis, Chlamydophila psittaci, and Chlamydophila pneumoniae. C. psittaci is widely distributed in nature, producing genital, conjunctival, intestinal, or respiratory infections in many mammalian and avian species. Genital infections with C. psittaci have been well characterized in several species and cause abortion and infertility. Although mammalian strains of C. psittaci are not known to infect humans, avian strains occasionally do so, causing pneumonia and the systemic illness known as psittacosis. C. pneumoniae is a fastidious chlamydial species that appears to be a common cause of upper respiratory tract infection and pneumonia, primarily in. | Chapter 169. Chlamydial Infections Three chlamydial species cause human infections Chlamydia trachomatis Chlamydophilapsittaci and Chlamydophilapneumoniae. C. psittaci is widely distributed in nature producing genital conjunctival intestinal or respiratory infections in many mammalian and avian species. Genital infections with C. psittaci have been well characterized in several species and cause abortion and infertility. Although mammalian strains of C. psittaci are not known to infect humans avian strains occasionally do so causing pneumonia and the systemic illness known as psittacosis. C. pneumoniae is a fastidious chlamydial species that appears to be a common cause of upper respiratory tract infection and pneumonia primarily in children and young adults and is a cause of recurrent respiratory infections in older adults. Studies have also linked C. pneumoniae infection to atherosclerotic cardiovascular disease and perhaps to asthma. No animal reservoir has been identified for C. pneumoniae it appears to be an exclusively human pathogen spread via the respiratory route through close personal contact. C. trachomatis is also an exclusively human pathogen and was identified as the cause of trachoma in the 1940s. Since then C. trachomatis has been recognized as a major cause of sexually transmitted and perinatal infection. Chlamydiae are obligate intracellular bacteria that are classified in their own order Chlamydiales Fig. 169-1 . They possess both DNA and RNA have a cell wall and ribosomes similar to those of gram-negative bacteria and are inhibited by antibiotics such as tetracycline. A unique feature of all chlamydiae is their complex reproductive cycle Fig. 169-2 . Two forms of the microorganism the extracellular elementary body EB and the intracellular reticulate body RB participate in this cycle. The EB is adapted for extracellular survival and is the infective form transmitted from one person to another. EBs attach to susceptible target cells usually .

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