Most common causes of meningitis?

[shan564]

It seems like different resources have different answers regarding the most common causes of meningitis.

First Aid 2012 says that the most common cause is Strep pneumoniae in all age groups except for newborns, where it's Strep agalactiae.

When I was listening to Goljan neuro during my 2nd-yr neuro block, he said "all other resources are wrong, I'm right, here's the answer" (can't remember what it was). But those lectures are several years old now.'

HY Neuro says that it's H. flu in young children and N. meningitidis in young adults.

Now that we have a vaccine for H. flu, I can understand that its prevalence should have decreased. The meningococcal vaccine is still pretty new and not widely used. I think the pneumococcal vaccine is more widely used.

And I've had conflicting answers from UW and Kaplan Qbank.

Anybody have any suggestions regarding what we need to know?

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[Ronin786]

It seems like different resources have different answers regarding the most common causes of meningitis.

First Aid 2012 says that the most common cause is Strep pneumoniae in all age groups except for newborns, where it's Strep agalactiae.

When I was listening to Goljan neuro during my 2nd-yr neuro block, he said "all other resources are wrong, I'm right, here's the answer" (can't remember what it was). But those lectures are several years old now.'

HY Neuro says that it's H. flu in young children and N. meningitidis in young adults.

Now that we have a vaccine for H. flu, I can understand that its prevalence should have decreased. The meningococcal vaccine is still pretty new and not widely used. I think the pneumococcal vaccine is more widely used.

And I've had conflicting answers from UW and Kaplan Qbank.

Anybody have any suggestions regarding what we need to know?

I know its not the H. Influenzae because of the vaccine like you mentioned (there was actually a question about that somewhere). I think now its Strep Pneumo like FA said, but I haven't verified that.

 

[sanityonleave]

It seems like different resources have different answers regarding the most common causes of meningitis.

First Aid 2012 says that the most common cause is Strep pneumoniae in all age groups except for newborns, where it's Strep agalactiae.

When I was listening to Goljan neuro during my 2nd-yr neuro block, he said "all other resources are wrong, I'm right, here's the answer" (can't remember what it was). But those lectures are several years old now.'

HY Neuro says that it's H. flu in young children and N. meningitidis in young adults.

Now that we have a vaccine for H. flu, I can understand that its prevalence should have decreased. The meningococcal vaccine is still pretty new and not widely used. I think the pneumococcal vaccine is more widely used.

And I've had conflicting answers from UW and Kaplan Qbank.

Anybody have any suggestions regarding what we need to know?

My understanding from various sources (most common, 2nd most common):

neonates -- group B strep, E. coli
children -- meningococcus, pneumococcus
adults -- pneumococcus, meningococcus

Obviously, there's some ambiguity there -- at some point pneumococcus and meningococcus supposedly swap spots in terms of prevalence, but it's hard to define a specific age or anything like that. I think that if you were given a question with a clear bacterial meningitis and asked to name the organism, they either would have to only have one of those two listed or give you more information (gram stain, etc) to allow you to make the dx.

 

[ijn]

HY Neuro is definitely wrong about H. flu unless it was published before 1986 or is talking about unvaccinated societies.

From eMedicine it's:

Age <3 months - GBS > E. coli K1 > Listeria > H. influenzae
Age 3 months - 18 years: N. meningitidis > S. pneumoniae > H. influzenae
Age 18 years - 50 years: S. pneumoniae > N. meningitidis > H. influenzae
Age > 50 years - S. pneumoniae > N. meningitidis > Listeria

 

[Phloston]

In terms of the thousands of MCQs I've come across so far between USMLE Rx, Robbin's Rapid Review of Pathology and University of Utah Webpath:

In neonates, it's as to be expected (in order of descending frequency): Group-B Strep, E. coli, Listeria

The important thing to remember about Listeria is that, when it comes to meningitis, it's bimodal, and also occurs in the elderly; with respect to pneumonia, it pretty much will only occur in neonates.

Now, as you guys have already mentioned, the incidence of Haemophilus influenzae meningitis has been drastically reduced given the introduction of the vaccine, so H. influenzae is never a top pick for meningitis in a child unless the vignette is explicit about immigrant status or the pt not having received vaccinations or "not knowing" about vaccination Hx. Other big red flags for H. influenza meningitis are recent/concurrent epiglottitis (easy) or otitis interna.

In general (and FA also agrees with this), in any patient >6 months of age, S. pneumonia is the most common overall cause of meningitis. However, in teenagers or college students it's Neisseria meningitidis.

 

[ijn]

Did you mean otitis media or interna? The H. flu vaccine only covers type b. It doesn't provide protection against the types that cause middle ear infections.

 

[shan564]

Cool, thanks for the feedback guys. I think the bottom line is "First Aid is the Bible"... and like somebody said, I'm sure they'd probably give us more information (i.e. Gram stain) if we're expected to choose between S. pneumo, H. flu, and N. meningitidis in a 12 year-old.