Chapter 22 - Microbial Diseases of the Nervous System Flashcards
What are meninges?
-3 continuous membranes: dura mater, arachnoid mater, pia mater
Subarachnoid Space
-between pia mater and arachnoid mater
-houses CSF
Blood Brain Barrier
-capillary system that prevents the passage of some substances but not others
Drugs cannot cross the BBB unless they are ____ soluable
lipid
What is a common lipid-soluable antibiotic?
chloramphenicol and sometimes penicillin in large amounds
Meningitis
inflammation of the meninges
Encephalitis
inflammation of the brain
Meningoencephalitis
when both the brain and meninges are inflamed
Initial Meningitis Symptoms
-fever
-headache
-stiff neck
Secondary Meningitis Symptoms
-nausea
-vomiting
Possible Progressions of Meningitis
-convulsions
-coma
-death
The progression of meningitis may only take ___ hours.
24
Kernig’s Sign
-a diagnostic tool in older or younger patients
-non-invasive
-stiffness when they bend their hamstrings
How is meningitis diagnosed?
spinal tap
What is a spinal tap?
-collection of a CSF sample from the spinal cord
-needle inserted between L3 and L4
Serology of Meningitis
-use a gram stain to diagnose
-keep the sample culture at storage temp and move quickly
What is used to treat bacterial meningitis?
3rd generation cephalosporins
*What is not reccomended to treat bacterial meningitis?
chloramphenicol due to adverse effects?
Haemophilus Influenzae
-aerobic
-gram-negative
-has a capsule
-member of normal throat microbiota
-can cause meningitis when it enters the bloodstream
How many strains of H. influenzae are there? Which most commonly causes disease? Why?
-6 strains classified by capsular antigens
-strain B causes 95% of cases
Hib Meningits occurs mostly in _______
children under age 4
Is there a vaccine for H. influenzae meningitis
Yes: HiB vaccine
-it can be effective by 6 months of age
-is given at 6 weeks of age
Meningococcal Meningitis is cause by which bacteria?
Neisseria meningitidis
N. Meningitidis
-aerobic
-gram-negative
-diplococcus
-has a capsule
-present in the nose and throat of carriers
How is N. meningitidis spread?
-droplet or contact
What are the strains of N. meningitidis? Which is the most common?
-strains A, B, C, W135, X, Y
-C is the most common
Who are commonly affected by N. meningitidis?
-children under 2
-college students
How long is the progression of N. meningitidis?
-it is fast
-may only be 24 hours
What are the primary symptoms of N. meningitidis?
throat infection that spreads to the blood stream
What are the secondary symptoms of N. meningitidis?
throbbing headache
Is there a vaccine for N. meningitidis?
yes
What are possible effects of N. meningitidis?
-necrosis that may lead to amputation
-deafness
-paralysis
-death
Petichiae
-rash associated with necrosis
Where does Streptococcus pneumoniae commonly reside?
-nasopharyngeal region
What % of the population are carriers of S. pneumoniae?
70%
Streptococcus pneumoniae
-gram-positive
-capsule
-diplococci
What is the leading cause of bacterial meningitis?
S. pneumoniae
Who is commonly affected by S. pneumoniae meningitis?
children between 1 month and 4 years
What is the mortality rate of S. pneumoniae meningitis in children?
8%
What is the mortality rate of S. pneumoniae meningitis in elderly?
22%
How many strains of S. pneumoniae are there?
90-92 strains
Is there a vaccine for S. pneumoniae?
-yes; the most common 20 strains have a vaccine
How does S. pneumoniae enter the blood stream?
-pneumonia
-otitis media
-surgery/trauma to the head or neck region
What is usually used to treat S. pneumoniae?
penicillin
Listeria monocytogenes
-gram-positive
-rod
How is L. monocytogenes spread?
-food, soil, water
-it is a psychotroph
When is L. monocytogenes dangerous?
during pregnancy (still born) or in immunocompromised people
Listeriosis is the _____ most common cause of bacterial meningitis.
fourth
What is the infant mortality rate of L. monocytogenes?
60%
What antibiotic is used for Listeriosis?
Penicillin G
When can E. coli cause meningitis?
in newborns
The bacteria that cause meningitis are usually carried by ________.
healthy people
What is used in prevention of meningitis?
-vaccine
-hygiene - not sharing drinks, lip balm, food utensils, etc.
Clostridium tetani
-obligate anaerobe
-endospores
-gram-positive
-rod
Where is C. tetani common?
soil contaminated with animal feces
What causes the symptoms of tetanus?
-A-B exotoxin: tetanospasmin
How does tetanospasmin act?
-it is released upon lysis of bacteria
-enters CNS via PNS or blood
-no inflammation
What does tetanospasmin block at the neuromuscular junction?
the relaxation pathway
What neurotransmitter does tetanospasmin inhibit?
GABA
What are the symptoms of Tetanus?
-muscle spasms
-lock jaw
-stiff neck
-opisthotonos: bent spine
How does Tetanus cause death?
-spasms of the muscles in the cardiovascular and respiratory system
What is needed for Tetanus to take action?
-anaerobic growth conditions ie. improperly cleaned deep wound caused by rusty nails
Is there a vaccine for Tetanus?
yes: DTaP
What type of vaccine is DTaP?
-toxoid - inactivated toxin
What bacteria causes Botulism?
Clostridium botulinum
Clostridium botulinum
-obligate anaerobe
-endospores
-gram-positive
-rod
Where is C. botulism found?
soil and many aquatic sediments
What does the botulinal A-B exotoxin do?
-blocks ACh at the neuromuscular junction
What does C. botulinum do?
-causes lost muscle tone and leads to flacid paralysis
Symptoms of Botulism
-abdominal distress
-nausea
-diarrhea or constipation
-blurred/double vision with dilated pupils
How long does C. botulinum take to show its full effect?
12-36 hours
What are the strains of C. botulinum? Which affect humans?
-strains A, B, C, D, E, F, G
-humans affected by A, B, E, F
Where do humans usually contract C. botulinum?
-canned foods (except for tomatoes)
-processed foods
Which bacteria causes Leprosy?
Mycobacterium leprae
What is another name for Leprosy?
Hansen’s Disease
M. leprae
-rods
-acid-fast
-grow optimally at 30℃
How does M. leprae act?
by invading the PNS
How is M. leprae transmitted?
by prolonged contact with an infected person
Paucibacillary/Tuberculoid/Neural Form of Leprosy
-entered by cell mediated immunity
What characterizes the paucibacillar form of leprosy?
-discoloured skin regions that have lost sensation
-surrounded by a border of nodules
Which leprosy is faster to recover from?
Paucibacillary (6 months) vs multibacillar (24 months)
Multibacillary/progressive Leprosy
-cell mediated immunity has failed
-progressive form
Multibacilliary Leprosy symptoms?
-disfuguring nodules all over the body
-mucous membrane of the nose infected
-lion face
-claw shaped hand
-loss of fingers and toes
What is the diagnostic test for leprosy?
acid-fast stain or blood test
How is leprosy treated?
-dapsone (sulfa drug)
-rifampin
-clofazimine
-usually all combined
What is clofazimine used for?
to minimize antibiotic resistance
What causes Polio(myelitis)?
poliovirus
How is polio transmitted?
by ingestion (fecal/oral contamination)
What are the initial symptoms of polio?
-headache
-sore throat
-fever
-nausea
Polio: People with good immunity
-transient infection
-show no symptoms
How many people are affected with the paralytic form of polio?
less than 1%
Polio: People with bad immunity
-when good immunity fails
-persistent viremia (enters blood)
-virus enters motor neurons
-grows in cell bodies to kill neurons
-leads to paralysis
How can polio cause death?
paralysis of respiratory muscles
Is there a polio vaccine?
yes, two actually
Salk Vaccine
-1955
-inactivated form of all 3 viruses
-IPV inactivated polio vaccine
-needs boosters
-has to be injected
Sabin Vaccine
-1963
-weakened version of the virus
-OPV oral polio vaccine
-less expensive
-no need for boosters
-1 in a million revert back and cause the actual disease
