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113lecture3406 - BIOLOGY 113 MICROBIOLOGY Lecture 34...

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BIOLOGY 113 - MICROBIOLOGY Lecture 34: Microbial Diseases of the Lower Respiratory Tract Pertussis is an infection of the lower respiratory system caused by the Gram-negative bacterium, Bordatella pertussis - B. pertussis colonizes the trachea, and an exotoxin it produces interferes with normal ciliary function, leading to accumulation of mucus (Tortora et al., Figure 24.8) - Pertussis, which can be quite severe, develops through a characteristic sequence = The catarrhal stage , in which the organism first infects the host, resembles a common cold = During the paroxysmal stage , when ciliary action is comprised and mucus accumulates, an infected person desparately attempts to cough up the mucus accumulations · This is where the common name for pertussis, whooping cough , arises · Most of us have never heard the sound of a patient in the paroxysmal stage of pertussis, but at one time it was known and greatly feared · The violence of the paroxysmal stage is adequate to result in broken ribs = Eventually, an adequate immune response leads to a long convalescence stage - Today, vaccination is recommended for all children = Earlier pertussis vaccines were whole killed B. pertussis cells; however there is some concern about neurological sequelae = Whole cell pertussis vaccine is being replaced with “acellular” subunit vaccines Tuberculosis is a lower respiratory system infection caused by the bacterium Mycobacterium tuberculosis - Cells of M. tuberculosis are quite resistant to dessication (perhaps due to their acid-fast cell wall (remember?!)), and are usually acquired by inhalation of the bacteria - Tuberculosis arises when cells of M. tuberculosis are ingested by alveolar macrophages (Tortora et al, Figure 24.10) = The macrophages may fail to kill the M. tuberculosis cells, which may actually multiply inside of the macrophages = A cell-mediated hypersensitivity response leads to formation of a tubercle , consisting of masses of tissue cells, leukocytes and M. tuberculosis cells = The tubercle may "wall off" the M. tuberculosis infection, leading to arrest of the infectious process -
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