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Ch 19 - Unit 4
Micro ch 19
| Question | Answer |
|---|---|
| Nervous system | two components – CNS (brain and spinal cord) and PNS (peripheral nerves) |
| Nervous system defenses | bony casings of brain/spinal cord; cushion of CSF; meninges surrounding brain, spinal cord; blood brain barrier; nervous system is an immunologically privileged site |
| Sterile tissue, so no normal microbiota; any microorganisms in PNS or CNS is a deviation from healthy state | normal biota of the nervous system |
| Meningitis | meninges inflammation; infection caused by many different microorganisms; serious forms caused by bacteria; diagnosed by lumbar puncture for CSF sample; typical symptoms headache, painful/stiff neck, fever, increased number of WBCs in CSF; altered cry |
| Neisseria meningitides | commonly known as meningococcus/meningenalcoccal meningitis; associated w/ epidemic forms; causes most serious form of acute meningitis; differentiated from other types by petechiae formation |
| Culture/diagnosis of Neisseria meningitidis | gram neg diplococci lined up side by side from CSF sample; rapid antigen tests, chocolate agar |
| Streptococcus pneumonia (pneumococcus) | most frequent case of community-acquired meningitis; very severe; no petechiae; detection of antigens in CSF with latex agglutination test; appear as lancet-shaped gram-positive diplococcic (end to end); multidrug resistant strains |
| Petechiae | what term refers to red or purple spots found on trunk area of some meningitis patients? |
| Haemophilus influenza (Hib type B) | causes severe meningitis; third leading cause of bacterial meningitis; most common cause of meningitis in unvaccinated children 2 mo to 5 yrs |
| Diagnosis of Haemophilus influenza | hard to culture; requires anaerobic conditions and chocolate agar; sensitive to drying, temperature extremes and disinfectants; tiny gram-negative pleomorphic rods |
| Listeria monocytogenes | not a common cause of meningitis, but frequent enough to mention; causes mild infection in normal adults; severe infection in immunocompromised pts, fetuses, neonates; ranges in morphology |
| Cryptococcus neoformans | fungal chronic form of meningitis; more gradual onset of symptoms; headache most common symptom with nausea and stiff neck; mainly affects immunocompromised pts. |
| Coccidioides immitis | true systemic fungal infection of high virulence; usually begins with pulmonary infection; prevalent in Arizona, California; abundant branching hyphae |
| Viral (aseptic) meningitis | majority of cases occur in children; 90% caused by enteroviruses; mortality less than 1%; generally milder than bacterial or fungal meningitis |
| Diagnosis of viral meningitis | treatment is supportive; virus is assumed cause if no other pathogen can be found; antibiotics can be started until cultures completed |
| Neonatal meningitis | meningitis transmitted in utero or during birth; premature babies more at risk; two most common causes S. agalactiae (lancefield group B strep); E. coli; Listeria also potential cuase |
| Streptococcus pneumonia | what is the leading cause of community acquired meningitis? |
| Meningoencephalitis | caused by Naegleria fowleri and Acanthamoeba; inflammation of the brain |
| Naegleria fowleri | amoeba in thick walled uninucleate cyst; infection start when amoeba enters nasal passages during aquatic activities; amoeba enters nasal mucosa, travels to brain; advancement is rapid, treatment futile; Primary ameobic meningoencephalitis (PAM) |
| Acanthamoeba | large amoeboid trophozoite with spiny pseudopods, double walled cyst; invades broken skin, conjunctiva, occasionally lungs, urogenital epithelia; causes Granulomatous ameobic meningoencephalitis (GAM) |
| Acute encephalitis | encephalitis almost always caused by viral infection; always serious condition; signs and symptoms vary but can include behavior changes, confusion, seizures |
| Arbovirus encephalitis | arthropod borne infection; most feed on blood of hosts; common outcome is acute fever with rash; forms are Western Equine Encephalitis (WEE) and Eastern Equine Encephalitis (EEE), California Encephalitis, St. Louis Encephalitis |
| Western Equine Encephalitis (WEE) | arboviral infection; appears first in horses, then humans; carried by mosquitos; extremely dangerous to infants, small children |
| Eastern Equine Encephalitis (EEE) | arboviral infection; endemic to eastern coast of N. America and Canada; usually appears first in horses and caged birds; very high case fatality rate |
| California Encephalitis | arboviral infection; may be caused by two different viral strains; children living in rural areas are primary target group |
| St. Louis encephalitis (SLE) | arboviral infection; most common of all American viral encephalitides; epidemics occur in US Midwest and south. |
| West Nile Encephalitis | arboviral infection; emerged in 1999 |
| St. Louis Encephalitis | what is the most common cause of acute encephalitis in the US? |
| Herpes Simplex Virus | Can cause encephalitis in newborns born to HSV-positive mothers; Prognosis is poor |
| Subacute Encephalitis | Symptoms take longer to show up and are less striking; Most common cause Toxoplasma, Measles infection, Prions |
| Toxoplasma gondii | obligate parasite spread in cat feces; flagellated protist that can cross placenta; causes subacute encephalitis |
| Subacute sclerosing panencephalitis | stems from measles infection; can appear years after initial measles infection; is direct viral infection of neural tissue |
| Transmissible spongiform encephalopathies (TSEs) | neurodegenerative diseases with long incubation periods but rapid progression once they begin; Creutzfeldt-Jakob disease; Gerstmann-Strussler-Scheinker disease; fatal familial insomnia |
| Rabies | slow, progressive zoonotic disease; mammalian infection; characterized by fatal encephalitis; average incubation time is 1 to 2 months or more; prodromal phase of fever, N, V, headache, other nonspecific symptoms |
| Furious rabies | periods of agitation, disorientation, seizures, twitching; spasms in neck and pharyngeal muscles lead to hydrophobia; progresses to coma phase and results in death |
| Dumb rabies | pt is not hyperactive but is paralyzed, disoriented; progresses to coma phase, results in death |
| Poliomyelitis | acute enterovirus infection that is neurotropic; virus is ingested, shed in feces; can cause flaccid paralysis infrequently; effective vaccines are Salk (inactive) and Sabin (attenuated) |
| Tetanus (lockjaw) | caused by Clostridium tetani; gram+ spore forming rod; releases a powerful neurotoxin (tetanospasmin) which block inhibition of muscle contraction, results in spastic paralysis |
| Botulism | caused by Clostridium botulinum; endospore forming neurotoxin that blocks release of neurotransmitters; three forms are food-borne; infant, and wound |
| African Sleeping Sickness | caused by Trypanosoma brucei; flagellated protist with tsetse fly vector; spreads systemically in blood and lymph; eventually causes CNS damage and altered behaviors; long asymptomatic period |
| Proper canning of food | what is the best way to prevent food-borne botulism in adults? |
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michellerogers
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