(exam 2) ch 22 microbial diseases of the nervous system Flashcards
what are the two main divisions of the nervous system?
1) central nervous system (CNS)
2) peripheral nervous system (PNS)
what is the central nervous system (CNS) ?
consists of the Brian and spinal cord; it is the control center of the body
what is the peripheral nervous system (PNS) ?
consists of nerves that branch from the CNS; nerves from the branch of from CNS and serves as communication lines
what are the meninges?
continuous membranes that protect the brain and spinal cord
what are the three layers of the meninges and where are they positioned?
1) outer— dura mater
2) middle — arachnoid mater
3) inner— pia mater
_________ mater is the layer of the meninges is the outer potion.
dura mater
_________ mater is the layer of the meninges that is in the middle.
arachnoid mater
_________ mater is the layer of the meninges that is in the inner portion.
pia mater
what is cerebrospinal fluid (CSF)?
fluid in the subarachnoid space (between arachnoid and Pia mater) that acts as a ‘cushion’
what is the blood brain barrier?
layer of endothelial cells that prevent solutes in circulating blood from non-selectively crossing into CNS (effective at keeping pathogens out)
what are two of the most common routs of Central Nervous System (CNS) invasion?
via the bloodstream and lymphatic system
what can alter the permeability of the blood brain barrier?
inflammation
what three things does the central nervous system have low levels of?
low levels of
1) complement
2) circulating antibodies
3) phagocytic cells
what is meningitis?
inflammation of the brain meninges
what is encephalitis?
inflammation of the brain
what is meningoencephalitis?
inflammation of both the brain meninges and the brain
(as an overview) what is meningitis caused by?
can be caused by a variety of pathogens (bacteria, viruses, fungi, or protozoa); viral meningitis is more common but usually mild
what are the symptoms of meningitis?
Triad of fever, headache, and a stiff neck; followed by nausea and vomiting. Symptoms may progress to convulsions and coma (neurological specific)
Haemophilus influenzae type b, neisseria meningitides, and streptococcus pneumoniae are all three species of what?
three species of bacterial meningitis
what do these three species, Haemophilus influenzae type b, neisseria meningitides, and streptococcus pneumoniae have in common?
they all have a capsule
how does death usually occur from bacterial meningitis?
death from shock and inflammation (due to endotoxin (gram - ) and cell wall release (gram +); survival often results in neurological damage
what is the structure of Haemophilus influenzae type b (Hib) Meningitis?
gram negative, aerobic bacteria; (opportunistic) in normal throat bacteria and can enter the blood stream. Its pathogenicity is due to capsule antigen type b
what is another name for Haemophilus influenzae type b?
Hib meningitis
what group is Hib meningitis most common?
occurs mostly in children 6 months to 4 years
is there prevention for Hib meningitis?
yes, prevented by the Hib vaccine
what is the structure of neisseria meningitides Meningitis?
aerobic, gram negative diplococcus with a capsule; there are six serotypes associated with the disease. Microbiota of nose and throat in about 40% of people
what is another name for neisseria meningitides meningitis?
Meningococcal Meningitis
what are symptoms for neisseria meningitides meningitis? aka meningococcal meningitis
begins as a throat infection, RASH, and bacteremia; symptoms are mostly from endotoxin; death can occur within hours after fever onset - very rapid
where is neisseria meningitides meningitis (aka meningococcal meningitis) most common and what age group?
typically occurs in children under 2 yrs; highest incidence in “meningitis belt” which is in sub-saharan Africa
is there prevention for neisseria meningitides meningitis (aka meningococcal meningitis) ?
vaccination protects against 5/6 serogroups
what is the structure of streptococcus pneumoniae?
gram positive, encapsulated diplococcus; 70% of people are healthy nasopharyngeal carriers
is there another name for streptococcus pneumoniae?
pneumococcal meningitis
which of the three types of bacterial meningitis is the leading cause?
streptococcus pneumoniae (aka pneumococcal meningitis)
what two other things can streptococcus pneumoniae (aka pneumococcal meningitis) cause?
pneumonia and otitis media
what group is streptococcus pneumoniae (aka pneumococcal meningitis) most common in?
most common in children 1 month to 4 yrs
is there prevention for streptococcus pneumoniae (aka pneumococcal meningitis)?
yes, prevented by conjugated vaccine
how would you diagnose the most common types of bacterial meningitis?
sample of cerebral spinal fluid via a spinal tab or lumbar puncture; samples are used for gram staining, culturing, and latex agglutination tests
why do tests used to diagnose some of the most common types of bacterial meningitis require prompt and careful handling?
because pathogens in CSF do not survive storage or changes in temperature
what does the beginning standard treatment for the most common types of bacterial meningitis look like?
chemotherapy (antibiotics) are initiated before diagnosis; due to rapid disease progression and threat of mortality; use of broad spectrum antibiotics- more specific treatment after identification
what is the cause of listeriosis?
caused by Listeria monocytogenes
what is the structure of listeriosis?
gram positive rod; excepted in animal feces; wide distribution in soil and water; it is a psychrophile (food borne illness)
what are three notable virulence factors of listeriosis?
1) not destroyed by phagocytes
2) reproduces within them
3) moves directly between them
what are two forms of listeriosis?
1) adult infection
2) infection of fetus and newborn
what is adult infection of listeriosis?
mild or symptomless infection; can invade the bloodstream causing sepsis; meningitis is more common in the immunocompromised
what is infection with listeriosis of a fetus or newborn?
infects pregnant women, crossing the placenta and leading to stillbirth; diseases manifests weeks after birth usually meningitis (infant mortality rate ~60%)
why is listeriosis listed under a type of meningitis?
because if a fetus or newborn is infected it can result in meningitis after birth
what type of disease to the nervous system is tetanus?
bacterial disease
what is tetanus caused by?
clostridium tetani
what is the structure of tetanus?
gram positive, endospore-forming, obligate anaerobe; grows deep within wounds with anaerobic conditions
what is the disease state of tetanus?
infection causes no inflammation; bacteria do not leave infection site; tetanospasmin neurotoxin (bad toxin) released from bacterial cells and enters the CNS via blood or peripheral nerves
what are the effects of the tetanospasmin neurotoxin of tetanus?
blocks relaxation pathway in muscles causing muscle spasms - jaw muscles are usually affected early resulting in lock jaw (indicative of tetanus)
how does death typically occur from tetanus?
death occurs from spasms of respiratory muscles
is there prevention for tetanus?
yes, prevented by vaccination with tetanus toxoid (DTaP); stimulates antibodies that neutralize the toxin; booster is required every 10 yrs (40% of US adults are not protected)
what are alternative treatments for tetanus?
treatment with tetanus immune globulin (TIG) antibody again toxin; or infected tissue removed via debridement
what type of disease to the nervous system is botulism?
bacterial disease
what is the structure of botulism?
gram positive, endosperm forming, obligate anaerobe
what typically causes botulism?
caused from ingesting toxin through contaminated food
what is the toxin of botulism specific for?
specific for the synaptic end of the nerve and blocks release of the neurotransmitter acetylcholine, causing flaccid paralysis
lock jaw and muscle spasms are indicative of ________ whereas the ‘opposite’ flaccid paralysis (limb muscles) is indicative of _______.
tetanus; botulism
what are the symptoms of botulism?
difficulty swallowing, general weakness, blurred or double vision
how does death usually occur from botulism?
death usually from respiratory or cardiac failure
what are the three botulinal types??
1) Type A toxin
2) Type B Toxin
3) Type E toxin
which of the three botulinal types is the most virulent?
type A toxin; 60-70% fatality
what is type A toxin of botulism?
most virulent because it is made in proteolytic strains with heat resistant spores; Western US
what is type B toxin of botulism?
fatality 25% most common in Europe and eastern US
what is type E toxin of botulism?
spree are less heat resistant than other strains; produced by organisms in marine and lake sediments (Pacific Northwest, Alaska, and Great Lakes)
which of the three botulinal types is responsible for 50% of cases; which two is responsible for the other 50%?
type A is responsible for 50% of cases;
type B and type E are responsible for the other 50% of cases
why is botulism in adults not serious?
because in adults, Clostridium is outcompeted by normal intestinal microbes
why is botulism more serious in infants?
C. botulinum grows in infants due to lack of intestinal microbiota
what is wound botulism?
growth of C.botulism in wounds
how is botulism diagnosed?
diagnosed by inoculating mice with patient samples
what is the treatment for botulism?
supportive care (long recovery process); recovery requires regeneration of nerve endings (slow process); extended respiratory assistance and application of antitoxins (against toxins)
what is a therapeutic approach to botulism?
Botox; treatment of migraine, painful muscle contractions (Parkinson’s disease), involuntary eyelid twitching and there are purely cosmetic applications
how can botulism be prevented?
prevented with proper canning and the use of nitrates in food
what type of disease to the nervous system is leprosy?
bacterial disease
what causes leprosy?
Mycobacterium leprae
what is another name for leprosy?
Hansen’s disease
what is the structure of leprosy ( Hansen’s disease)?
acid-fast rod (waxy coating); grows best at 30 degrees celsius (prefers cooler areas of the body such as peripheral nerves and skin cells); able to survive macrophage ingestion and eventually invades nerve cells
what is the generation time for leprosy?
long generation time ~12 days
what is unique about leprosy?
has never bene grown on an artificially media; only on some animals
what are the two primary forms of leprosy?
1) Tuberculoid (neural) form
2) Lepromatous (progressive) form
what is Tuberculoid (neural) form of leprosy?
reflects effective patient immune response (can fight it off); loss of sensation in skin areas
what is Lepromatous (progressive) form?
less effective immune response (disease progresses past the tuberculoid stage); disfiguring nodules over the body; mucous membranes are affected
what is the cause of death usually from leprosy?
not from leprosy itself but from disease complications from having leprosy
how is leprosy transmitted?
transmission requires prolonged contact with an infected person or the inhalation of secretions (often years between infection and appearance of symptoms
how do we diagnose leprosy?
diagnosed with a skin biopsy, skin smear or blood test
what is the typical treatment for leprosy?
long term antibiotic treatment ranging from 6-24 months
