Bacterial meningitis Dr. Charles Prober discusses prudent prescribing of antibiotics in the context of bacterial meningitis with 4th year medical student Morgan Theis
- We're here at Stanford Medical School with 4th-year medical student Morgan Keyes and Dr. Charles Prober.
- MK: Okay, Dr. Prober, what are we going to talk about today?
- Dr: So Morgan, I thought we'd talk about Bacterial Meningitis in children.
- MK: Okay.
- Dr: And what I'd look to do in reflecting on bacterial meningitis (BC) is...
- ...go back to the lessons we learned in the prudent prescribing of antibiotics.
- Dr: a former video, a prior video.
- Dr: One of the things that was mentioned as a general principle in that particular video
- was trying to understand where the site of infection is in a child,
- in order to pick the right antibiotic and the right management.
- Dr: So in this case, since I'm referring to BC, the question might be:
- What would make you think that a child has BC?
- That is, what are the signs and symptoms of BC?
- Student: So this is thinking about the site, knowing that there is an infection in the
- cerebrospinal fluid (CBF), or fluid around the brain and spinal cord, you have to look at that
- in a variety of ways as a doctor?
- Dr: Exactly. One of the things that will make a physician suspicious that there might be
- an infection in the CBF or in the central nervous system (CNS),
- is that a child might not be behaving normally,
- that is, they might have an altered state of consciousness.
- E.g., they might be very, very sleepy; or, they might be very irritable
- Student: So the signs are irritability and/or sleepiness (lethargic),
- maybe even in a coma, which would be more advanced in the infection.
- Dr: And then the child would almost invariably have that fever associated with this illness.
- And, on the examination, when the physician examines the child,
- they might detect what are called "meningeal signs".
- And those meningeal signs include a stiff neck, especially if the child is over 1 or 2 years of age,
- Student: And how can you tell if someone has a stiff neck?
- Dr: What a physician will often due is hold the child behind the head and try
- try to flex the head on the neck, and stiff would be literally that:
- the child's neck would not bend when the head is elevated from the bed.
- Student: Wow, so it's literally where it stays linear, you can't curve it well.
- Dr; Exactly. The other meningeal signs that may be present in addition to the stiff neck are
- the child may have some seizures, abnormal movements.
- The child might also assume an abnormal posture, a stiffening of the body.
- So, not just the neck being stiff, but the rest of the body being stiff as well.
- And on examination of the neurologic system, the nervous system,
- the child might have "focal signs," that is, asymmetry between the two sides of the body.
- Student: Oh, and what kinds of things would you see that are assymetrical?
- Dr: It could be that one side of the body is weaker than the other,
- It could be that one of the body has different reflexes than the other side.
- These are all signs and symptoms which may be associated with BM,
- which would make the physician suspicious of the diagnosis of meningitis.
- Student: Okay, so we talked about some of the things you look for as a doctor. Now,
- going back a minute, you said something about BM, does that assume that there
- are other types of meningitis that we are not addressing in this lecture?
- Dr: That is a very important point. So, I am focusing on BM,
- there are other types of organisms, non-bacteria, that can cause meningitis,
- and the most prominent of those other organisms are viruses.
- So you can have a viral meningitis, sometimes referred to as aseptic meningitis.
- And that in fact is more common that bacterial meningitis, so it is very important to consider.
- There are also some parasites that can cause meningitis, and some fungi.
- The fungi and parasites are uncommon, but they may occur in abnormal immune systems
- Viral meningitis on the other hand is quite common.
- But for today I am focusing on bacterial meningitis.
- So you suspect the infection may be present based on those signs and symptoms.
- To prove, to determine whether meningitis is present,
- a cerebrospinal fluid (CSF) examination [must take place],
- and CSF is acquired by doing a lumbar puncture,
- putting a needle in the back to obtain fluid.
- Student: Is that also what a spinal tap is?
- Dr: That is also called a spinal tap
- When that is obtained, using a needle into the lumbar area,
- a fluid is then sent to the lab, where the fluid will be examined in different ways
- One is to look under the microscope and determine if there is an abnormal number
- of white blood cells present.
- Student: So abnormal meaning high or low?
- Dr: Meaning just high, actually.
- The normal number of white blood cells in the CSF is 0.
- So, high is something greater than 0. And with BM, it tends to be quite high.
- generally 1,000-2,000/mL.
- Glucose is also measured, and with BM the glucose tends to be low
- less than 40.
- Student: Why would it be low?
- Dr: It's low because with meningitis you have an abnormal penetrability,
- or lack of penetrability of the meninges, which are the covers of the brain,
- reducing the amount of glucose that is transported into the spinal fluid.
- Dr: And then most importantly, the fluid is examined with something called the Gram stain,
- a special kind of stain. A Gram stain can determine if bacteria are present.
- Student: So you're actually staining the bacteria.
- Dr: Exactly. And if sufficient bacteria are present the Gram stain will reveal those.
- And so, with BM, the 2nd prudent principle is to know the pathogen.
- So, if a spinal fluid is obtained, there is lots of white cells, your glucose is low,
- even with a negative Gram stain, one can guess the usual pathogens,
- because the list is short in normal children.
- And those bacteria, the short list, includes "Haemophilus influenzae" tybe B,
- 2nd, the Pneumococcus.
- Student: That's funny, it sounds like it causes pneumonia.
- Dr: It does cause pneumonia, indeed.
- 3rd: Meningicoccus.
- Dr: Those are the prominent bacteria in normal children with BM.
- The reason we're not seeing as much BM in 2011 as we were seeing 10 or 20 years ago,
- is we now have vaccination against each of those three pathogens.
- Student: We do?
- Dr: We do. We vaccinate against "H. Influ. B" starting at two months of age
- and by the time the child is about 1.5yrs, they're completely protected against that bacteria
- The Pneumo we also vaccinate against and it's very successful at reducing
- the frequency of pneumococcal meningitis--also given at 2 months of age.
- And Meningicoccus, the vaccination is relatively new and used in children who are older
- They're now 2yrs of age.
- So, we still can and do see cases of meningicoccal meningitis as it occurs
- in children under the age of 2.
- Those are the usual pathogens. In other parts of the world that don't use vaccines,
- those are the pathogens that will be prominent in causing BM.
- And knowing those pathogens, we go to the 3rd Principle of antibiotic prescribing,
- which is knowing antibiotic would potentially kill those bacteria.
- Student: Okay, so what should I call that category?
- Dr: Pathogen sensitivity, knowing which antibody would work against the likely bug.
- Student: That, you were mentioning in your last lecture,
- that varies by the location in the body, and the location in the world, where you're using it.
- Dr: It varies by the location of the world, but not by part of the body.
- And, fortunately, for the treatment of BM, to cover all three of the bacteria,
- two antibiotics cover all three of them, and I'll just mention the names as I end this.
- One antibiotic is Cefotaxin, and a reasonable facsimile is Ceftriaxone.
- And because some of the Pneumo are resistant to Beta-lactam drugs,
- Vancomycin is also used for suspected BM.
- Student: Okay, so we use Vancomycin if we think you have a bug that is resistant to other drugs?
- Dr: Exactly.
- Student: And there is a type of lab test you could do to find that out?
- Dr: Exactly. So those are the Principles of antibiotic prescribing, in terms of
- diagnosis of BM. 1) Knowing site of infection
- 2) What the pathogens are, and 3) knowing what antibiotic would work.
- Student: My last question, just because we learned about a tight barrier between
- the blood and the CSF, are these antibiotics listed here able to cross the barrier?
- Dr: An extraordinarily important question, which is another principle:
- You have to make sure that they can be delivered to the suspected site of infection.
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