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Micro Chap 26

Terms in this set (71)

Neuron
Nerve cell that transmits electrical impulses, communicate via neurotransmitters (chemical signaling)
Dendrite
Receives information
Cell body
"The command center", contains nucleus
Axon
Thin extension, transmit signals to another cell
Synapse
Region between cells
Central Nervous System (CNS)
Brain and spinal cord
skull & vertebral column
The Central Nervous System is well protected by what?
Cerebrospinal fluid (CSF)
Circulates over the surface of the brain & spinal cord, cushions and supports, transports nutrients, generally sterile, no normal microbiota ("blood-brain barrier")
Meningitis
Inflammation of meninges
dura mater, arachnoid mater, and pia mater
Three layers of meninges
Encephalitis
Inflammation of the brain
Meningoencephalitis
Inflammation of both the meninges and the brain
Peripheral Nervous System (PNS)
Bundles of axons, carry information to and from the CNS
Pneumococcal meningitis
Signs and symptoms: mild cold, sudden onset of severe, throbbing headache, fever, pain and stiffness of neck and back, nausea, vomiting, deafness, confusion, loss of consciousness, coma, death
Streptococcus pneumoniae
- Gram-positive diplococcus
- Causes pneumonia & leading cause of meningitis in adults, capsules protects from phagocytosis, enter bloodstream and pass into CSF
- Damage may be due to inflammatory response: fluid accumulation causes brain swelling
Causative agent of Pneumococcal meningitis
penicillin or 3rd generation cephalosporin, polyvalent vaccine (23 strains) is available
Treatment and prevention of Pneumococcal meningitis
Meningococcal meningitis
Signs and symptoms: similar to pneumococcal meningitis, purplish spots on skin due to bleeding under the skin, endotoxic septic shock
Neisseria meningitidis
- Gram-negative encapsulated diplococci
- Inhaled in airborne droplets, enter bloodstream and reach meninges
- Endotoxin causes vasodilation & capillary leakage (purple spots), drop in blood pressure
Causative agent of Meningococcal meningitis
penicillin or ceftriaxone, age-specific vaccines available
Treatment and prevention of Meningococcal meningitis
Meningococcal meningitis
_____________ ____________transmitted person-to-person, mostly sporadic in the US (highest incidence in "meningitis belt")
Haemophilus influenzae meningitis
Signs and symptoms: mild cold, progress to severe headache, fever and vomiting, stiff neck in older children
Haemophilus influenzae
- Gram-negative rod
- Unencapsulated strains do not enter bloodstream, but encapsulated strains can cause bacteremia & meningitis
- Hib in children: 90% case fatality rate if not treated, 5% with treatment
Causative agent of Haemophilus influenzae meningitis
3rd generation cephalosporins, Hib vaccine given at 2 months of age
Treatment and prevention of Haemophilus influenzae meningitis
Neonatal meningitis
Signs and symptoms: fever, vomiting, irritability, poor feeding, lethargy, & bulging fontanels (during 1st month of life)
Streptococcus agalactiae (most common), E. coli (encapsulated strain), Listeria monocytogenes
- From bacteria that colonizes the mother's birth canal
- Inflammation increases intracranial pressure, block CSF flow, lead to abnormal CSF build up that compress and damages brain tissue causes nervous tissue damage and brain abscess
Causative agent of Neonatal meningitis
antibacterial medications, test mother's vagina for streptococci before birth
Treatment and prevention of Neonatal meningitis
Listeriosis
Signs and symptoms: generally asymptomatic or mild in most healthy people, fever, muscle aches, sometimes nausea or diarrhea
- Can enter blood & cause meningitis: fever, headache, stiff neck, and vomiting
- Pregnant women: miscarriage
Listeria monocytogenes
- Gram-positive motile rods
- Can grow at refrigeration temperature, foodborne illness
Causative agent of Listeriosis
antibacterial medications, food safety practices (phage)
Treatment and prevention of Listeriosis
Hansen's disease (leprosy)
Signs and symptoms: pigmentation changes, increased or decreased sensation, visible enlargement of nerves on arms and legs, pain followed by numbness, thickening of nose and ears and deep wrinkling of facial skin
Tuberculoid leprosy
Rarely transmitted to others, develops and limits spread, nerve cells are damaged by immune cells, lead to deformities, resorption of bone, and skin ulcerations, stopped by immune system, but damage is permanent
Lepromatous leprosy
Easily transmitted to others, bacterial growth unrestricted, can be fatal if untreated
Mycobacterium leprae
- Acid-fast rod-shaped bacterium
- Slow grower with incubation time up to 3 years
- Reservoir can be armadillos
Causative agent of Hansen's disease (leprosy)
multiple antibiotics long-term (6 month to 2 years), no vaccine available
Treatment and prevention of Hansen's disease (leprosy)
Botulism
Signs and symptoms: incubation time 12-36 hours, dizziness, dry mouth, blurred or double vision, progressive paralysis, deteriorating muscle coordination, death
Botulism
Most lehal neurotoxin known to man
Clostridium botulinum
- Gram-positive rod, anaerobes, spore-former (spores survive boiling, can germinate in favorable environment), produce lethal neurotoxin (a few grams could kill everyone in the United States)
- Foodborne (most common globally), intestinal (infant botulism), and wound botulism
- Outbreaks commonly occur because of improperly home-canned foods
Causative agent of Botulism
induce vomiting, antitoxin intravenously, artificial respiration, proper canning
Treatment and prevention of Botulism
Viral meningitis
Signs and symptoms: fever, severe headache, sensitivity to light, stiff neck, nausea, vomiting, sore throat, chest pain, swollen salivary glands, skin rash, generally recover in 7 to 10 days
usually coxsackie viruses and echoviruses
- Non-enveloped RNA viruses
- Fecal-oral route transmission, infects mucus membranes, spreads to the bloodstream, & causes meningitis, typically less severe than bacterial meningitis
Causative agent of Viral meningitis
no specific treatment, avoid crowed pools
Treatment and prevention of Viral meningitis
Viral encephalitis
Signs and symptoms: fever, headache, vomiting, disorientation, localized paralysis, seizures, coma, & possibly death
Viral encephalitis
West nile
usually arboviruses
- Enveloped ssRNA viruses
- Transmitted by mosquitoes, mites, or ticks
- Birds and rodents can serve as reservoirs
- Including LaCrosse encephalitis virus, St. Louis and West Nile encephalitis viruses, and equine encephalitis viruses
- Infects cells of blood-brain barrier, enter brain, destroy brain tissue
Causative agent of Viral encephalitis
no proven treatment, repellents & insecticides
Treatment and prevention of Viral encephalitis
Poliomyelitis
Signs and symptoms: about 95% asymptomatic (immune system conquers infection), headache, fever, stiff neck, nausea (5% cases), destruction of motor neurons, muscle pain and spasms, paralysis (1%), paralysis of respiratory muscles (severe cases), post polio syndrome (muscle degeneration 15-50 years post-recovery)
Polioviruses (3 types)
- Non-enveloped ssRNA viruses
- Ingested, infect throat and GI tract, invade bloodstream, rarely binds to motor neurons and destroy cells
Causative agent of Poliomyelitis
"iron lung", newborns are protected for 2-3 months by maternal antibody, usually exposure during this time results in mild infection & lifelong immunity, Salk vs. Sabin vaccines
Treatment and prevention of Poliomyelitis
Rabies
Signs and symptoms: incubation time 1 to 2 months, fever, head and muscle aches, sore throat, fatigue, nausea, tingling or twitching sensation
- Progresses rapidly to agitation, confusion, hallucinations, seizures, encephalitis, increased salivation, difficulty swallowing, respiratory failure, and death
- Changes behavior: desire to bite & fear of water
rabies virus
- Bullet shape, enveloped, ssRNA
- Transmitted via animal saliva introduced into bite wounds, multiplies, enters sensory neuron, goes to spinal chord and brain
- Main reservoir: wild animals (raccoons, bats, skunks, foxes, etc.), vaccinate domestic cats & dogs
Causative agent of Rabies
Injection of anti-rabies antibody (passive immunity), followed by 4 injections of inactivated vaccines, no effective treatment once symptoms appear, avoid infected animals
Treatment and prevention of Rabies
cryptococcal meningoencephalitis
Signs and symptoms: difficulty thinking, dizziness, intermittent headache, fever, vomiting, weight loss, paralysis, seizures, and coma, progresses much faster in immunodeficient individuals
Cryptococcus gattii (causes disease in healthy individual) and Cryptococcus neoformans (opportunistic)
- Found in soil and bird droppings
- Yeasts, form capsules, resists immune response, inhaled & starts in the lung (mild or no symptoms), multiply, enter the bloodstream, infect meninges & brain
Causative agent of cryptococcal meningoencephalitis and where is it found
Amphotericin B, does not reliably cross blood-brain barrier, 70% success (except in AIDS patients), no vaccine
Treatment and prevention of cryptococcal meningoencephalitis
African sleeping sickness
Signs and symptoms: incubation time 1 week, tender nodule at site, enlarged lymph nodes, recurrent fevers, loss of interest, decreased activity, indifference to foods, slurred speech, falls asleep constantly, comatose, & death
Trypanosoma brucei
- Flagellated protozoan, transmitted by tsetse flies
- Acute disease: East Africa, rhodesiense subspecies causes death within 6 months from heart failure
- Chronic disease: Central & West Africa, gambiense subspecies, years may pass before death, often from secondary infections
Causative agent of African sleeping sickness
Difficult, medications have toxic side effects, insecticides
Treatment and prevention of African sleeping sickness
Toxoplasmosis
Signs and symptoms: mostly asymptomatic in healthy individuals, sore throat, fever, enlarged lymph nodes & spleen (10-20%, similar to mononucleosis)
- In immunodeficient individuals: reactivation of latent infection, more than 50% leads to encephalitis
- Fetal toxoplasmosis: via placenta, if mother gets infected for the 1st time during pregnancy can cause miscarriage, effects less severe later in the pregnancy
Toxoplasma gondii
- Obligate intracellular protozoan with complex life cycle
- Reproduces in final host (cats), excreted via feces into soil, most infections acquired by ingestion or inhalation
Causative agent of Toxoplasmosis
mostly not treated in healthy individuals, sulfa drug if immunocompromised, pregnant women should avoid cat litter boxes
Treatment and prevention of Toxoplasmosis
Primary amebic meningoencephalitis
Signs and symptoms: incubation time 1 week, similar to meningitis (headache, fever, stiff neck, & vomiting), followed by seizures, coma, and death
Naegleria fowleri
- Free-living protozoa that prefers warm fresh water
- Penetrates the skull along the olfactory nerves, multiplies and migrates to the brain, & destroys nervous tissue
Causative agent of Primary amebic meningoencephalitis
usually fatal, miltefosine (investigational use), avoid swimming in contained water
Treatment and prevention of Primary amebic meningoencephalitis
Transmissible Spongiform Encephalopathies(TSE)
Spongy appearance of infected brain tissue ("mad cow disease" and "scrapie")
- TSE in humans mostly occur as Creutzfeldt-Jakob Disease (CJD): behavioral changes, anxiety, insomnia, fatigue, muscle jerks, lack of muscle coordination, memory loss, dementia, & death (can be inherited or transmitted human-to-human)
- Another form: kuru, from cannibalism practices in New Guinea
Prions (proteinaceous infectious particles)
- Highly resistant to disinfectants (including formaldehyde), heat, UV, & ionizing radiation
- Prions aggregate in insoluble masses called 'plaques' in the brain, death of neurons produces spongy appearance
- Commonly transmitted by eating contaminated tissue
Causative agent of Transmissible Spongiform Encephalopathies(TSE)
No treatment, always fatal, avoid eating animals that show neurological symptoms
Treatment and prevention of Transmissible Spongiform Encephalopathies(TSE)
Primary amebic meningoencephalitis
In the News: In SC Hannah Collins infected with _______ ________ _________ from swimming in the Edisto River
-Botulism
-Hansen's disease
Disease's of the PNS
-Poliomyelitis
-Meningitis
Spinal cord diseases
-Meningitis
-Encephalitis
-Rabies
-African sleeping sickness
-Primary amebic meningoencephalitis
-Transmissible Spongiform Encephalopathies(TSE)
Disease's of the brain
c) Haemophilus influenzae meningitis
A 7 week old baby developed a mild cold that progresses to severe fever and meningitis, gram negative rods are observed in the blood, which of the following infections does the child most likely have?
a) Pneumococcal meningitis
b) Meningococcal meningitis
c) Haemophilus influenzae meningitis
d) Neonatal meningitis
e) Listeriosis
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