ID-Nervous system Flashcards
Major functions of the CNS and PNS
Sensory, integrative, motor. CNS inclused brain and spinal cord, PSN is cranial and spinal nerves (does not have meninges)
Defenses of the nervous system
Mainly structural (encased in bone), cushion of CSF, blood-brain barrier (filter system for brain and spinal cord)
Normal biota of the nervous system
NO NORMAL BIOTA, any microorganisms in the PNS or CNS is a deviation from a healthy state
Meningitis
Inflammation of the meninges (layers around the brain and spinal cord). Many different microorganisms can cause this infection. Spinal tap is performed to obtain CSF if meningitis is suspected. Typical symptoms include headache, painful or stiff neck, fever, increased number of WBC in the CSF.
Neisseria meningitides
Gram negative diplococci lined up side by side commonly known as meningococcus. Often associated in outbreaks of meningitis in prisons, barracks, etc. Causes the most serious form of acute meningitis. Mostly happens in children. Highly contageous, breathed in.
Virulence factors of neisseria meningitides
Bacterium enters blood stream and has the ability to penetrate the meninges. Pathogen releases endotoxin and activates white blood cells and damages blood vessels. Small number of cases become fulminant disease which is located everywhere in the body and has a high mortality rate. Can have a capsule and igA protease. Sudden onset- fever, chills, delirium, shock, coma. Cardiac failure can happen in hours.
Transmission of neisseia meningitides
Bacteria is acquired through close contact with infected secretions or droplets. Nasopharynx is the portal of entry. Bacterium are engulfed by epithelial mucosa and penetrate blood vessels and move to meninges.
Epidemiology of neisseia meningitides
Sporadic or epidemic incidence in late winter and early spring. Humans only-harbor in nasopharynx and act as the resevoir. Highest risk group is small children.
Diagnoses of neisseria menigitides
Suspicion of meningitis constitutes a medical emergency. CSF, blood, and nasopharyngeal samples are gram stained. Looking for characteristic diplococci, may need differential testing to determine bacterial strain.
Prevention of neisseria meningitides
Infection rate in most populations is only about 1%-due to natural immunity to meningococcus. Penicillin G treats this given in high doses intravenously until fewer and fewer bacteria are present. Preventitive therapy is with rifampin or tetracycline-for people who have come into contact but have no symptoms. Vaccine is required for high risk populations such as dorms. Provides protection for 10 years.
