Meningitis pt.1 Flashcards
What is meningitis?
Inflammation of the meninges
What are the meningies?
Three membranes that cover the brain and spinal cord and include (from most superficial to deepest):
- Dura mater
- Arachnoid mater
- Pia mater
Where is the CSF found?
It is found in the subarachnoid space found between the pia and arachnoid mater
Aside from the arachnoid space, what other anatomical space can found in the CNS?
A potential space known as the subdural space and according to some authors, it contains a very thin layer of fluid
Where is the main site of meningitis infection?
The subarachnoid space with involvement of the CSF
According to the appearance of the CSF, how can one differentiate between possible etiologies of meningitis?
- Transparent CSF suggests a viral meningitis
- Purulent (cloudy) CSF suggests a bacterial meningitis
What are the possible infectious etiologies of meningitis?
They include viral, bacterial, fungal, parasitic/protozoal
What are examples of parasitic/protozoal organisms that can cause meningitis?
They include:
- Plasmodium
- Toxoplasma
- Amoeba (Naegleria fowleri)
- Angiostrongylus
- Hydatid
- Cysticercosis (Taenia solium tapeworm)
What are examples of fungal organisms that can cause meningitis?
They include:
- Cryptococcus
- Histoplasma
- Aspergillus
- Candida
- Mucormycosis
- Coccidiosis
What is the most common etiological form of infectious meningitis?
Viral is the most common, followed by bacterial (still common), with fungal and parasitic/protozoal being rare
What are the most common bacteria causing bacterial meningitis?
They include:
- Streptococcus pneumoniae
- Group B Streptococcus
- Neisseria meningitidis
- Haemophilus influenzae
- Listeria monocytogenes
- Escherichia coli
H. Influenzae b, S. pneumoniae, N. meningitidis
cause together 75-80% of all bacterial meningitis
What is considered to be the most important bacterium causing meningitis?
Haemophilus influenzae
What type of bacteria is Haemophilus influenzae?
Gram negative facultative anaerobic capnophilic coccobacillary
What is a facultative anaerobic organism?
An organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent
Is Haemophilus influenzae preventable?
Yes, vaccination is available
Which age group does Haemophilus influenzae affect?
Mostly children 6 months to 4 years old
What type of bacteria is Neisseria Neisseria meningitidis?
Gram negative aerobic capsuled diplococci
What is another name for Neisseria meningitidis?
Meningococcus
What does capnophilic organisms?
Microorganisms that thrive in the presence of high concentrations of carbon dioxide (CO2)
How common is the neisseria meningitidis bacterium in the population?
- Widespread in general population
- Estimated to be found in the nasopharyngeal flora of 3% to 25% of healthy individuals
Where is neisseria meningitidis bacterium found in carriers?
Mostly found in the naso-pharynx
Which serogroup of neisseria meningitidis is most common in the United States and Europe?
Serogroup B in the USA and Serogroup C in Europe
Who is neisseria meningitidis vaccine recommended to?
- Universally recommended beginning at age 11 with boosters at 16 years
- It is also recommended down to the age of 9 months for anyone at high risk for meningococcal
disease (complement deficiency, asplenia, HIV infection)
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What are the serogroups of neisseria meningitidis based on?
Serogroups are based on the
polysaccharide capsule
Which neisseria meningitidis serotypes are the most clinically relevant?
- The most important disease-producing serogroups are A, B, C, W-135, and Y
- Group A causes widespread epidemics
How N.meningitidis transmitted?
Transmission occurs by inhalation of aerosolized respiratory droplets
What promotes transmission of N.meningitidis?
- Close, prolonged contact
such as occurs in families and closed populations promotes transmission. - The estimated attack rate among family members residing with an index case is 1000 times higher than
in the general population; this fact is evidence of the contagious nature of meningococcal
infection - Other factors that foster transmission are contact with a virulent strain and host susceptibility (lack of protective antibody)
What are typical settings of large N. meningitidis outbreaks?
Typical settings of larger outbreaks are schools,
dormitories, and camps for military recruits. In these close living circumstances, N meningitidis
spreads readily among newly exposed individuals, but disease develops only in those who
lack group-specific antibody.
What are problems with the current meningococcal vaccine?
- Does not protect against serogroup B (failure of the group B polysaccharide to be immunogenic at all, recognized as self by the host), Group B causes up to one-third of all disease, so no vaccine that omits
it is likely to be completely successful - The “hole” created by absence of a group B component could have epidemic potential
- There is less experience with these protein-conjugate vaccines which is why the recommended starting age is 11. In practice the age is being slowly and cautiously dropped down
How can disease arise in individuals in contact with N. meningitidis?
Disease may be endogenous (respiratory microbiota) or transmitted from a case
by respiratory droplets
What is the current vaccine against N.meningitidis?
Meningococcal Conjugate Vaccine Quadrivalent (MCV4) which protects against serotypes A, C, Y, and W-135
Which age group does N.meningitidis affect?
Most disease occurs in children 6 months to 5 years old ( 6 months and 2 years of age being the peak) with a second peak at 18 to 25 years of age
