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Nervous system infections Outline (2)

Nervous system infections Outline (2) - Diseases of the...

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Diseases of the nervous system Central nervous system (CNS) -the brain and spinal cord Peripheral nervous system (PNS) –all nerves that branch off from the spinal cord. Meninges –three continuous membranes that cover the brain and the spinal cord Meningitis -inflammation of the meninges. Encephalitis –inflammation of the brain. Blood-brain barrier –Membrane barrier that limits chemical and cellular access to the brain. Single layer of tile-like endothelial cells that line the inner surfaces of capillaries in the brain 1. Bacterial Meningitis: For all causes of BACTERIAL meningitis, symptoms are largely the same regardless of causative agent. (Table 27.3) A. In the bloodstream, the bacterial capsule resists attack by neutrophils, and the classic complement pathway. Receptors for pili and other bacterial surface molecules help penetration into the CSF space. Because the CSF has relatively low levels of antibodies, complement, and WBCs, the infection flourishes. B. Fever severe headache, and stiff neck, followed by nausea and vomiting. May progress to convulsions and coma. Death occurs due to shock and inflammation. A spinal tap and gram staining necessary for identification and eventual treatment. When bacterial meningitis is suspected, broad spectrum  antibiotics should be given immediately, without waiting for diagnostic test results. C. Streptococcus pneumoniae     , gram pos. diplococci (Fig. 27.4) 90 different capsules !  Remember, upwards  of 25% of us are carriers.  The primary virulence factor is the capsule. 1) Accounts for 30-50% of bacterial  meningitis , may result as a sequelae of pneumonia. 2) Fatality rate is high, Primarily strikes adults. 3) Antibiotic resistance a factor. In some areas of the US, as many as 30% of pneumococcal isolates are not susceptible to penicillin. 1
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4) Vaccine can reduce incidence of disease. D. Neisseria meningitides     gram neg. diplococci  – All Neisseria are gram neg. diploccoci  (Table 27.1, Fig.  27.6).  This is the organism which causes epidemics 1) Exist in the nasopharynx of about 5% of the population and spread by respiratory droplets and  close contact. For unknown reasons, only a small fraction of carriers develop meningitis. Second  most likely cause of meningitis. 2) Usually starts with a throat infection which leads to bacteremia, and then meningitis.   a. Most symptoms are caused by endotoxins., specialized pili enable meningococci to bind to  nasopharyngeal cells for transport across the mucosal barrier.
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