Chapter 25 Central Nervous System Infections Flashcards
How can pathogens traverse the blood-brain barrier?
- growing across, infecting the cells that comprise the barrier
- being passively transported across in intracellular vacuoles
- being carried across by infected WBCs
What is meningitis?
inflammation of the membranes surrounding the brain
Which type of cells are mainly present in CSF in the case of septic (purulent) meningitis?
mainly neutrophils
Which type of cells are mainly present in CSF in the case of aseptic meningitis?
mainly mononuclear
How do CSF protein counts compare in septic versus aseptic meningitis?
septic: high (>100)
aseptic: moderately high (50-100)
How do CSF glucose levels compare in septic versus aseptic meningitis?
septic: <45 low
aseptic: normal
What causes meningococcal meningitis?
Neisseria meningitidis
What is the most common cause of bacterial meningitis?
Streptococcus pneumoniae
what are the important causative agents of non-viral meningitis?
- Neisseria meningitidis
- Haemophilus influenzae
- Streptococcus pneumoniae
- Escherichia coli
- Listeria monocytogenes
- Mycobacterium tuberculosis
- Cryptococcus neoformans
What are the top three causative agents of bacterial meningitis?
- Haemophilus influenzae type b (Hib)
- Neisseria meningitidis
- Streptococcus pneumoniae
Which virulence factors does Streptococcus pneumoniae have in common with N. meningitidis and H. influenzae, and which ones is it missing?
All three have a capsule and IgA protease, whereas Neisseria meningitidis and Haemophilus influenzae also have pili, endotoxin, and outer membrane proteins
Describe the quadrivalent vaccine for Neisseria meningitidis
targets A, C, Y, W serotypes of the polysaccharide capsule
Describe the bacterium that causes meningococcal meningitis
Neisseria meningitidis is a Gram-negative diplococcus. Uses pili to attach to epithelial cells in nasopharynx, carried asymptomatically by up to 20% of the population
What does a low CSF glucose level relative to serum glucose indicate and why?
bacterial infection, since bacteria use flucose feor metabolism
Which meningitis-causing bacteria are spread from person to person spread by droplet infection, and are frequently found in areas of overcrowding?
Neisseria meningitidis
In which groups does Streptococcus pneumoniae commonly cause bacterial meningitis?
children and the elderly
Describe Streptococcus pneumoniae
Gram-positive coccus, normal flora in throat, alpha-hemolytic
Why do babies not respond to PP23 meningococcal meningitis vaccine?
not conjugated
In what groups does Listeria monocytogenes cause meninigitis, and what are the symptoms?
in immunocompromised adults
-symptoms: about 4 days after flu like symptoms: fever, personality change, tremors, muscle contractions, seizures
What is/are the most frequent cause(s) of neonatal meningitis?
group B beta-hemolytic streptococci (GBS)
What is the histology of miliary tuberculosis?
lesions are millet seed-sized (1 mm diameter)
- yellowish, firm areas without grossly visible caseation necrosis
- structure of tubercles with minute areas of caseation necrosis
Describe the pathogenesis of Mycobacterium tuberculosis meningitis
Bacilli spread in CSF-> tuberculin reaction in meninges -> meningitis -> adhesions -> CSF pathways locked, nerves and blood vessels damaged
Which pathogen causes fungal meningitis?
Cryptococcus neoformans
Which populations are at risk for fungal infections? What is the incubation period?
people with weakened immune systems; 2-11 months
How is C. neoformans infection diagnosed?
antigen detection; antibody detection
What is the treatment for cryptococcus? What is the mechanism of these medications?
IV amphotericin B (binds ergosterol and disrupts membrane permeability) and flucytosine (inhibits DNA synthesis) for 2-10 weeks, followed by oral fluconazole or itraconazole (inhibits sterol synthesis) for 6-12 months
Which pathogen causes valley fever, what is the incubation period, and the symptoms?
-Coccidiodes immitis (Endemic to SW USA)
-1-3 week incubation period
-flu-like symptoms
fatigue, fever, cough, fever, shortness of breath, night sweats, muscle aches/joint pain, rash on upper body or legs, headache
How can Valley Fever be diagnosed?
complement-fixing antibodies in the serum
What is the difference between encephalitis and menigitis?
encephalitis is inflammation of the brain, whereas meningitis is inflammation of the lining of the brain/meninges.
Name protozoa that enter via skin and/or respiratory tract and cause meningitis
Naegleria fowleri, Acanthamoeba spp., Balamuthia mandrillaris
How does viral meningitis compare to bacterial meningitis?
milder, with headache, fever and photophobia, but less neck stiffness
What symptoms would someone with encephalitis present with?
abnormal behavior, confusion, seizures, altered consciousness, N/V, fever
Which virus causes severe and fatal encephalitis in a human bitten by an infected monkey?
B-virus
Which virus was a common cause of encephalitis before vaccine was released, and had one of three serotypes that caused 75% of paralysis?
poliovirus
Which pathogen cause an outbreak of hand-foot-mouth infection with a high rate of meningoencephalitis for children under age 5 and a 19% mortality rate
enterovirus 71
describe the structure of poliovirus
positive sense ssRNA virus with icosahedral symmetry
Describe the pathogen that causes rabies encephalitis
rhabdovirus is an enveloped, bullet-shaped ssRNA virus
Which paramyxovirus causes encephalitis and is transmitted from pig to human and human to human?
How are pigs infected?
Nipah virus exposure to (eating food contaminated with) secretions of fruit bat and flying fox which carry the virus
What causes changes in behavior in rabies encephalitis?
viral invasion of the limbic system
What type of vaccine is given to prevent rabies?
active immunization with killed diploid cell-derived rabies virus
Describe togaviruses
enveloped, +ve sense RNA viruses
~30-45% of people with encephalitis caused by which virus will die from the disease?
Eastern equine encephalitis virus (EEEV)
Which flavivirus infection is related to dengue, yellow fever, and West Nile virus?
Japanese encephalitis virus, transmitted by mosquitoes (pigs and birds and intermediate hosts), ~70K cases/yr in India and China, 30% mortality rate, vaccines available
What is the inflammatory demyelinating condition of the PNS associated with a variety of infections, as well as with immunization with non-infectious material?
Guillain-Barre syndrome
What neurological diseases have a possible viral etiology?
- MS
- ALS
- Parkinson’s
- schizophrenia
- dementia
What clinical presentation may children with severe CNS disease from parasites show?
ocular disease, hydrocephalus, convulsions, intracerebral calcifications
How does Plasmodium falciparum cause cerebral malaria?
RBCs containing the asexual stages adhere to the walls of capillaries
Why does Toxocara infection result in granuloma formation in brain and retina
humans are dead-end hosts
What happens in the brain when humans ingest Echinococcus granulosus eggs?
embryos emerge and migrate through gut to blood vessels and develop into hydatid cysts in brain as well as in liver, lungs, kidney
Which pathogen causes cysticercotic encephalopathy if the brain is heavily infected?
Taenia solium, the pork tapeworm
Which pathogen crosses the blood brain barrier causing sleepiness, confusion, and behavioral changes? Does it have a vector?
Trypanosoma brucei gambiense
yes; tsetse fly
How does Clostridium botulinum cause ‘floppy babies’?
toxin blocks acetylcholine release from peripheral nerves
How does Clostridium tetani cause uncontrolled muscle spasms?
toxin tetanospasmin blocks releas of inhibitory mediators in spinal synapses
How does the blood-brain barrier compare to the blood-CSF barrier?
The blood-brain barrier has thick basement membrane, no fenestrations in the endothelium, and the blood vessel is surrounded by astrocyte footplates (glial processes). Whereas the blood-CSF barrier has a thin basement membrane, fenestrated endothelium, and the blood vessel is surrounded by tightly joined choroid plexus epithelium
Who is susceptible to Cryptococcus neoformans infections, what kind of pathogen causes the infection, what is the incubation period, and what symptoms are involved?
People with weakened immune systems are susceptible to this fungal infection with an incubation period of 2-11 months.
Symptoms if in lungs: cough, shortness of breath, chest pain, fever
Symptoms if in brain: headache, fever, neck pain, N/V, sensitivity to light, confusion or changes in behavior
How can a Cryptococcus neoformans infection be diagnosed and treated (describe the mechanisms)?
Dx: Antigen detection and antibody detection
Tx: IV amphotericin B (binds ergosterol and disrupts permeability of membrane) and flucytosine (inhibits DNA synthesis) for 2-10 weeks.
Followed by oral fluconazole or itraconazole (inhibits sterol synthesis) for 6-12 months.
Describe spongiform encephalopathies, including their causative agent.
Spongiform encephalopathies are caused by scrapie-type agents (prions). Appearance of spongiform appearance of nervous tissues, caused by vacuolation and plaque formation.
- Infections in animals seem to have originated from sheep and goats with scrapie which has been present in Europe for 200-300 years.
- Affected animals itch and scrape themselves against posts for relief
