Microbial Disorders of the Nervous System - Meningitis to Polio (Week 6) Flashcards
True or False: Meningitis can be bacterial or viral
True
An inflammatory bacterial infection of the meninges (specifically, the two internal ones - the pia and arachnoid mater) that induces meningial swelling, which restricts CSF flow and puts pressure on the organs, causing nausea, pain, vomiting, and reduced brain function
bacterial meningitis
What are some symptoms of bacterial meningitis if the infection is in the spinal cord?
- muscles of neck become stiff
- motor control reduced
What are some symptoms of bacterial meningitis if the infection is in the brain (encephalitis)?
- sensory perceptions are decreased
- behavioural changes
- coma
- death
How do we test for bacterial meningitis?
lumbar puncture (aka “spinal tap”)
Note: this involves extracting CSF
negative (normal) = clear CSF
positive = cloudy CSF
What are some of the regular disease causing bacteria of bacterial meningitis?
- Streptococcus pneumoniae*
- Haemophilus influenzae
- Listeria monocytogenes
- Neisseria meningitidis*
Note: these account for 90% of bacterial meningitis cases
What are some of the opportunistic members of NORMAL MICROBIOTA that can cause bacterial meningitis?
- Staphylococcus aureus
- Streptococcus pyogenes
- Klebsiella pneumoniae
Neisseria meningitidis causes what type of meningitis?
meningicoccal meningitis
What are some of the virulence factors of Neisseria meningitidis?
- fimbriae
- polysaccharide capsules
- lipooligosaccharide (with Lipid A/Endotoxin)
Neisseria meningitidis has a unique characteristic known as ___________
blebbing (bacteria shedding membrane, releasing Lipid A –> causes fever, shock, etc)
What is the leading cause of meningitis?
Streptococcus pneumoniae
What are some of the virulence factors of Streptococcus pneumoniae?
- phosphorylcholine* (main virulence factor; attachment to cells of lungs, meninges, blood vessels; triggers endocytosis)
- capsule
- secretory IgA protease (note: IgA protects mucosal linings)
- pneumolysin (inactivator of lysosomal enzymes)
a gram +ve coccobacillus found in soil, water, and many animals, often obtained through contaminated food/drink
Listeria monocytogenes
True or False: Listeria monocytogenes causes meningitis in immunocompromised individuals, but only a mild flu in healthy adults
True
How does Listeria monocytogenes avoid immune system detection?
by dividing inside macrophages and epithelial cells
(harder to attack them)
Listeria monocytogenes hijacks a cell’s ____________ to help propel it into another cell, so that it never has to leave a cell
actin
Which bacterial causes of meningitis can be inhaled from respiratory droplets?
- Neisseria meningitidis
- H. influenzae
- S. pneumoniae
Which bacterial cause of meningitis can come from unpasteurized milk, cheese, and meat?
Listeria monocytogenes
How does bacterial meningitis spread to the meninges?
Starts from infection of lungs, sinuses, or inner ear
How to prevent meningitis?
- avoid undercooked veggies, unpasteurized milk, undercooked meat, and all soft cheese
- people living in dorms should receive vaccinations
What disease is caused by Mycobacterium leprae?
Hansen’s disease (aka leprosy)
What is the optimal temperature for growth for leprosy?
30 degrees C
Note: therefore the chilly parts of your body (e.g., peripheral nerve endings, earlobes, nose, tips of fingers and toes)
True or False: Signs of leprosy/Hansen’s disease may not be present for 10-30 years, but once the population becomes big enough, the immune system will aggressively attack
True
Note: usually severe at this point and may lead to nerve damage
What disease is caused by Clostridium botulinum toxin?
Note: this is NOT an infection
botulism
Note: the toxin is packaged within an endosphore
What are the 3 types of botulism?
1) foodborne
2) infant
3) wound
What are the symptoms of foodborne and wound botulism?
- paralysis of all voluntary muscles
- blurred vision
- nausea
- death from respiratory paralysis
What are the symptoms of infant botulism?
- may infect GI tract due to absence of microbiota
so isn’t this technically an infection?
How does botulism toxin work?
- acts at the neuromuscular junction
- blocks the fusion of neurotransmitter (Ach) vesicles to the axon terminal membrane
- because the Ach can’t be released, the muscle fibres don’t receive a signal to contract
- leads to muscle paralysis
What condition is caused by Clostridium tetani?
tetanus
How does Clostridium tetani enter?
endospores enter through breaks in skin
What are the signs/symptoms of tetanus?
- tightening of jaw and neck muscles
- difficulty swallowing
- fever
- muscle spasms
How do we treat tetanus?
- aggressive treatment of wound
- antibiotics
How do we prevent tetanus?
vaccination
True or False: Unlike in botulism, tetanus toxin (tetanospasmin) causes the muscles to OVER contract
True
Note: tetanus toxin blocks the release of INHIBITORY neurotransmitters, therefore cannot get inhibitory signal (therefore muscle always getting APs and cannot relax)
True or False: West Nile Never came to North America in the early 1900s
False
Only just recently arrived in 1999
True or False: West Nile virus infects 100s of birds, 37 mosquitos, and 18 other vertebrates (including humans and horses)
True
How does west nile virus transmit?
- between birds (i.g., crows) and mosquitoes
- then between mosquitoes and humans/horses
True or False: West nile virus can be spread from human to human
False
Only from mosquito to human. Humans are “dead-end” hosts
What is the incubation period of west nile virus (WNV)?
3-14 days before symptoms present
How many people infected with west nile virus get flu-like illness (West Nile Fever)?
20-30% of infected
Of these people who get West Nile FEVER, 1/150 experience NEUROINVASION:
- headache
- ocular manifestations
- muscle weakness
- cognitive impairment
- polio-like flaccid paralysis
- 10% mortality
(therefore can be serious if one of these people)
How many people infected with west nile virus show no symptoms at all?
70-80%
What type of human cell does the west nile virus infect?
Langerhans dendritic cells
What is an environmental risk factor for west nile virus?
draught season
How can be prevent contracting west nile virus?
- mosquito repellant/proper clothing
Poliomyelitis is caused by _______________
poliovirus
True or False: Poliovirus has a DNA genome
False
It has an RNA genome
What are some characteristic long term symptoms of poliomyelitis?
- limb atrophy and weakness
- difficulty breathing
How does one contract poliovirus?
through ingesting fecally-contaminated material (fecal-oral route)
virus passes through digestive system and replicates in the intestinal mucosa
when it exits, it exits on the basal surface, which gets it in contact with the blood
establishes a viremia and travels through lymph nodes
How is poliovirus shed?
fecal waste
In what percentage of cases does the poliovirus get into the CNS?
1% of cases
from muscle –> axon –> somatic motor neuron –> spinal cord
When these somatic motor neurons get killed off, this is what causes muscle atrophy
True or False: If the poliovirus kills off enough somatic motor neurons, this can lead to not only muscle atrophy but muscle PARALYSIS
True
What are the three phases of the polio?
incubation (7 days) –> systemic (5 days) –> neural (5 days)
True or False: Humans are the only known reservoir of poliovirus
True
What is a complication of poliomyelitis?
post-polio syndrome
you basically experience paralysis decades later, due to lower # somatic motor neurons from polio + natural aging process that further decreases # somatic motor neurons
25-40% cases of polio, can take place 30-40 years after polio, NOT an infectious process
The _________________ vaccine was the first polio vaccine in the 1950s, and the _______________ vaccine was the second vaccine in the 1960s.
Both lead to a dramatic decrease in polio cases… completely eliminating from the Americas/Europe and very close to being eradicated world wide.
inactivated,
live oral
True or False: Polio typically has only minor symptoms for infants and adults but due to the emergence of modern plumbing and sewer systems, and consequently, less exposed immune systems, people had become more immunosusceptible in the 1900s
True
