CNS infections Flashcards
Other than inflammation of the meninges, how else can meningitis be defined?
Infection of the cerebrospinal fluid
What is the main difference in symptoms between encephalitis and meningitis?
In meningitis there is not altered conscious level or focal neurological signs
What is the usual cause of brain abscesses?
Normally bacterial but can be parasitic
In which 2 ways may invasion of microorganisms into the brain occur?
Blood borne invasion
Invasion via peripheral nerves
In viral, TB and cryptococcal infection of the brain, the white cell count in CSF is raised, what is the predominant type of white cell?
Lymphocytes
How does CSF glucose differ in viral, TB and cryptococcal brain infection?
Normal or reduced
How does CSF protein differ in viral, TB and cryptococcal brain infection?
Normal or increased
How does CSF glucose and protein change in bacterial infection?
Glucose is reduced
Protein is increased
Neisseria meningitidis is one of the main causes of bacterial meningitis, what kind of bacteria is it?
Gram negative diplococci
How many capsular types of Neisseria meningitidis, what are the 5 most common types?
13 capsular types
A, B, C, W135 and Y are most common
Other than by culturing how else can Neisseria meningitis be identified?
By nucleic acid amplification - PCR
What is the natural habitat of Neisseria meningitidis?
Nasopharynx
What 2 factors affect the survival ability of Neisseria meningitidis in the bloodstream?
1) Presence of a capsule - protects against complement-mediated bacteriolysis and phagocytosis
2) Ability to modify host cell inflammatory processes ie. host cell cytokine production
Once Neisseria meningitidis has crossed the BBB where does it multiply?
In the subarachnoid space
Meningococcal meningitis is caused by which organism?
Neisseria meningitidis
Meningoccal meningitis is more common in which age groups?
Children below 9 months
Another small peak at ~18 years
What 4 infections can Neisseria meningitidis commonly cause?
1) Fulminant (severe and sudden onset) septicaemia
2) Septicaemia with purpuric rash
3) Septicaemia with meningitis
4) Pyogenic (purulent) meningitis with no rash
Other than the 4 most common, what 4 other infections can Neisseria meningitidis cause?
1) Chronic meningococcal bacteraemia with arthralgia
2) Focal sepsis
3) Conjunctivitis
4) Endophthalmitis (inflammation of the internal coats of the eye)
What is septicaemia?
Bloodstream infection
What is the treatment for Neisseria meningitidis infection?
Ceftriaxone, cefotaxime - culture bacteria in the lab and if sensitive to penicillin then step down to penicillin
Early treatment, intensive care
Chemoprophylaxis is used in contacts of people with invasive Neisseria meningitidis infection, what 2 anti-microbials are used?
(Used for close or ‘kissing’ contacts)
Rifampicin
Ciprofloxacin
Is there an available vaccine against Neisseria meningitidis?
Yes for groups A, C and W135 but none against group B
The ‘African meningitis belt’ refers to massive epidemics across Africa caused by which group of Neisseria meningitidis?
Group A
Haemophilus influenza bacteria is unable to grow in the absence of what?
Blood or certain constituents of blood
What kind of bacteria is haemophilus influenza?
Small, pleomorphic, gram negative cocci-bacilli or bacilli
Does haemophilus influenza have a capsule?
Some strains produce a polysaccharide capsule
Which type of haemophilus influenza causes the most invasive disease?
Type B
In which part of the body is haemophilus influenza commonly carried in humans?
Throat carriage
How does haemophilus influenza commonly invade the bloodstream?
1) Carried in the throat
2) Invasion of submucosa
3) Invasion into blood stream
Haemophilus influenza can cause meningitis most commonly in which group?
Infants - > 2months - 2 years
Which type of haemophilus influenza has a capsule?
Type B
What is the treatment for haemophilus influenza?
Ceftriaxone, cefotaxime
Ampicillin
B-lactamase producing strains are common
Which antimicrobial is used in chemoprophylaxis of contacts of invasive haemophilus influenza infection?
Rifampicin
Is there a vaccine available against haemophilus influenza?
Type B conjugate vaccine available
Led to a dramatic reduction in the incidence of invasive disease
What kind of bacteria is streptococcus pneumoniae?
Gram positive cocci, cells in pairs
What does streptococcus pneumoniae require for growth?
Requires blood or serum for growth
What is the normal habitat of streptococcus pneumoniae and how is it transmitted?
Normal habitat is human respiratory tract - transmission is via droplet spread
Streptococcus pneumoniae causes meningitis more commonly in which groups?
Elderly and immunocompromised
What 2 antimicrobials are used in the treatment of streptococcal meningitis?
Ceftriaxone and cefotaxime
Penicillin resistant strains common in some parts of the world
Is there chemoprophylaxis for contacts of invasive streptococcal meningitis?
No
Is there a vaccine available against streptococcus pneumoniae?
Conjugate vaccine available against common serotypes
What are the 3 common bacteria causing meningitis?
1) Neisseria meningitidis
2) Haemophilus influenza
3) Streptococcus pneumoniae
Other than antimicrobials what other drugs can be used in meningitis, particularly in streptococcus pneumoniae?
Steroids
Neonatal meningitis is commonly caused by which 3 organisms?
1) Group B haemolytic streptococci
2) Escherichia coli
3) Listeria monocytogenes
What is the course of infection leading to meningitis in n neonates?
1) Early (5 days) - usually meningitis
What 3 antimicrobials are used to treat neonatal meningitis?
1) Cefotaxime
2) Ampicillin
3) Gentamicin
What are 8 possible complications of meningitis?
1) Death
2) Overwhelming sepsis
3) Raised intracranial pressure
Longer term problems
4) Deafness
5) Delayed development
6) Seizures
7) Stroke
8) Hydrocephalus
What 3 types of organisms can lymphocytic meningitis be caused by?
1) Most commonly viral meningitis
2) Spirochete (spiral shaped bacteria) - treponemal, borrelia
3) TB
What virus can cause meningitis that may lead to paralysis but can be prevented with vaccination?
Polio virus
What are the 3 epidemiological risk factors for TB meningitis?
1) Immunocompromised
2) Alcoholic
3) Comes from an endemic area
What is the treatment for TB meningitis?
1) 12 month standard TB treatment
2) Steroids beneficial
What is meant by acid fast bacilli stain used for TB?
Add stain and try and wash away with acid and alcohol but the cell walls of the TB retains the stain
By what 2 methods can TB be detected?
1) Ziehl Neelsen stain
2) Fluorescent Ab stain
Brain abscesses caused by bacteria which has spread from the middle ear or sinuses will commonly be caused by what bacteria?
Streptococci anaerobes
Brain abscesses caused by bacteria which has spread from the blood stream are commonly caused by what bacteria?
Staphylococcus aureus
What investigation is needed to confirm a diagnosis of brain abscess?
Brain imaging
Cryptococcal meningitis is a common problem in which group of patients, is it lymphocytic or polymorphic?
Those with late stage HIV - lymphocytic
What is the treatment for cryptococcal meningitis?
Prolonged course of treatment with amphotericin, flucytosine or fluconazole
Is encephalitis more commonly caused by bacteria or viruses?
usually viral
What is the most common cause of encephalitis worldwide?
Japanese encephalitis
Which group does Japanese encephalitis commonly affect?
Children
What is the prognosis for Japanese encephalitis?
1/3 die in acute illness
1/3 left with severe long term neurological disability
1/3 recover
Is Japanese encephalitis preventable?
Yes by vaccine
What is the prognosis for rabies encephalitis and how is it spread?
100% mortality
Spread by dog, fox and bat bites
Is rabies encephalitis preventable?
Yes by vaccination
Clostridium tetani causes what condition?
Tetanus (lock jaw)
What are the 5 main symptoms of tetanus?
1) Tonic muscle spasms
2) Trismus (spasm of the jaw muscles)
3) Opsithotonus (spasm of muscles causing backward arching of the head)
4) Respiratory difficulties
5) Cardiovascular instability
What kind of bacteria is clostridium tetani?
gram positive spore forming bacillus - strict anaerobe
How is clostridium tetani spread?
Organism which is widespread in the soil - implantation of contaminated soil into wound which may be major or minor
How does clostridium tetani cause the symptoms of tetanus?
1) Organism is non invasive but produces tetanospasmin
2) Toxin genes plasmid encoded
3) Toxin spreads via blood stream and retrograde transport
4) Toxin binds to ganglioside receptors and blocks release of inhibitory interneurons
5) Get convulsive contraction of voluntary muscles
What is the most common entry site of clostridium tetani to the body?
Foot
Name a toxin mediated CNS infection?
Tetanus
What is the treatment for tetanus?
Antitoxin - horse or human Penicillin or metronidazole Drugs for spasms Muscle relaxants Respiratory support
What can be used in the prevention of tetanus?
Toxoid (chemically modified toxin which is no longer toxic but is still antigenic and can be used as a vaccine)
What type of cell culture is used to identify streptococcus pneumonia?
Optochin test