Wow welcome to another MedCram lecture we're going to talk about Mrs a
infections here's what we're going to cover in the next four videos a brief
review of the differences between MSS a mrs a health care required mrs a and
community-acquired mr NSA will talk about the risk factors for mrs a
variance factors that typically make community-acquired mrs a worse than
hospital acquired pneumonia and will illustrate chest x-ray and CT findings
for mrs a pneumonia we'll talk about the clinical decision and diagnosis of mrs a
will compare vancomycin and linezolid for primary treatment options we'll also
talk about tell events and pros and cons and how it compares with vancomycin and
wide variety of agents may not be ready for primary consideration for mrs a
pneumonia we'll also talk about specific treatment considerations for
community-acquired mrs a and finally we'll tie it all together and review
before we talk about mrs a let's talk a little bit more general about infections
from Staphylococcus aureus staff and Latin means grape-like and then caucus
means like a grouping so this would be like a grape like grouping this is what
it looked like under the microscope and then aureus if you'll notice the
periodic table au is the symbol for gold and they notice that these colonies were
were gold and looking and so that's where we came up with Staphylococcus
aureus it's basically a very opportunistic bacteria it likes to
invade likes to go in and it can cause some very bad infections specifically in
the skin but also in the lungs and there's two major types or branches of
Staphylococcus aureus two major types of infections and it has to do with the
antibiotics that we use for a Staphylococcus aureus in both situations
of course it's a Staphylococcus aureus it will have a sa but the antibiotic
specifically that we use as a litmus test to find out whether or not this
staph aureus of is one type or another it's something called methicillin
otherwise can be used as oxacillin methicillin is the one that we use so
the ones that are sensitive to methicillin are called methicillin
sensitive Staphylococcus aureus and the ones that are resistant are called
methicillin-resistant Staphylococcus aureus so we have MSS a specifically and
Mrs a obviously Mrs a is not sensitive to methicillin and as a result of that
there's a whole class of antibiotics which can't be used against it it's
resistant to it it does nothing for it and the patient gets worse and this can
be seen in a number of different situations so methicillin sensitive
basically you can use a wide variety of different antibiotics mr sa is also
likewise divided into two groups which you may not be aware of there are
actually two types of mrs a one of them is known as the healthcare acquired M R
s a and the other one is known as the community-acquired M R s a and as it
turns out the community acquired mr sa is very very variant we'll talk about
that a little bit in just a bit the hospital acquired or healthcare acquired
mr sa is the ones that we typically see in the hospital but there's been more of
a blurring and we'll talk a little bit more about that so just be aware that
there's a healthcare associated mr sa and there is a community acquired mr sa
both of these are resistant to methicillin of course and then there's
methicillin sensitive we're going to talk a little bit about the epidemiology
we'll talk about the clinical features specifically as it relates to pneumonia
and I'll talk about the treatment and the treatment options that we have today
for this ok so we're going to talk about Mrs a just in general
Mrs a has been described all the way back to the 1960s and what they noticed
is that this strain of staphylococcus aureus was resistant to methicillin
that's how it got its term mr sa this incidence since the 1960s has definitely
increased without a question and in fact to the point now
if you would take a look at all the different types of strains for instance
in an intensive care unit about 60 percent of the staff of coccus aureus is
M RSA and this is this is growing and that accounts for about 90,000
infections per year so that's pretty significant now how does this work
there's something called penicillin binding proteins so penicillin binding
proteins specifically the penicillin binding protein 2a is coded by the gene
you may see this the MEC a gene and this MEC a gene which can be you know shared
around to different types of staph aureus they can all get this penicillin
binding protein which basically in activates methicillin so that
methicillin doesn't work so it all boils down to this penicillin binding protein
to a coda for by the MEC a gene and this is a mobile genetic elements for two
bacteria that don't normally have this ability to be resistant to methicillin
so you can get new generations it can be transferred and so this is a real
problem because if we have a lot of this going around we get more and more
antibiotic resistance so that's M RSA let's talk a little bit about the
different types of M R say that we alluded to earlier okay so there's the
healthcare acquired mr si let's talk about that one first the thing that
you've got to know about these two different types is that they were
identified based on the risk factors and in the environment in which they were
found and so they're named for their history and so you can see that the
healthcare acquired mr si was a particular strain of mr sa that was seen
in hospitalizations and so typically we would see these in people who have been
in the hospital for greater than 48 hours or within 12 months of being in
the hospital if they came in from the outside so in other words these were
people that were discharged to a healthcare facility or they came back
into the hospital but have been just recently hospitalized or in a nursing
of some sort or they were in the hospital and this happened two or three
four or five days after they were hospitalized now this has been
increasing in prevalence since oh the 1980s 1990s once it got to around the
2000s 2010 the prevalence started to even out maybe even go down a little bit
and we'll talk about why and I can allude to that the community-acquired
amorous a started to increase in terms of that if you word however to compare
Mrs a to M s sa okay especially this healthcare acquired mr saye the
healthcare acquired mr sa had patients that had increased length of stays in
the hospital increased mortality that's comparing it to the MS SA and this makes
sense right because if you have someone with MS si you're going to generally
speaking select the right antibiotic up front even if you're giving them like
Rocephin or ampicillin or something like that there's a good chance especially if
you're using one of these second-generation penicillins
like methicillin etc that you're going to hit the MS sa with Mrs a unless
you're using Vanko in these situations or other antibiotics that we'll talk
about later you're not going to get and therefore mortality is going to go up
especially if it's a very severe infection okay let's talk about CA Mrs a
and I think we're going to get into this a little bit later but the two big areas
and this is the biggest one that this was seen was in the skin and the soft
tissue this was pretty big about in the early 2000s mid 2000s what was happening
was is that they were starting to see in high schools and colleges that gym
equipment football equipment were getting colonized with this type of CA
Mrs a and these students were coming down with horrible mrs a infections that
were a lot more difficult to treat than the type of infections that they were
seeing in the hospital this was also seen in intravenous drug users
so in the 1980s we're also getting these types of infections and why was it that
the community-acquired in other words the strain of mr sa that was seen in the
community why was it acting so different well it's because of this thing called
the the pant on Valentine factor and this is a very lends factor I don't want
to get too much into it but there was also causing leukocidin toxins and
there's different antibiotics that could make the toxins worse and there's other
antibiotics that could make it better there's still some argumentation about
which type of antibiotic is better for this the bottom line that you need to
know is that the type of strain of mr sa that was seen in the community and is
actually increasing and in fact overtaking this strain that was seen in
the hospital is very very variant and very aggressive difficult to treat and
has a increased mortality the other thing that you can see especially if
this causes a pneumonia is you get a severe necrotizing pneumonia that
sometimes the only way you can make them better is to surgically remove that
portion of the lung so the thing is is that because these strains were first
identified this one here in the community and this one here in the
hospital we kind of looked at this differently you know if the mr sa is
coming from the hospital is generally going to be a hospital-acquired mr sa
and of course if it's coming from the community we got to be concerned that
it's a much more aggressive and very lended community acquired mr sa the fact
of the matter is now is we're starting to see a blurring of these two types so
in other words we could actually see this strain occurring in the hospital
setting and we could see this strain occurring in the community setting and
so it's very important to look at the types of strains and see how the
behavior of this of this bacteria is let's talk about risk factors what are
the risk factors that you've got to look for in page
specifically to be worried about mr essay in general so let's talk about
these risk factors and they kind of go for both of course the most obvious is
going to be you know previous antibiotic use because we know that this causes
resistance specifically cephalosporins which is kind of scary because we use
that all the time and community acquired pneumonia but the one that is associated
the most is fluoroquinolones like levaquin let's just say in general it's
fluoroquinolones and that one is big-time associated and we use that all
the time in community acquired pneumonia the other one is HIV and this
specifically goes for the community acquired em RSA believe it or not things
that wouldn't surprise you hemodialysis catheters these are
catheters that are left in place they get em RSA all the time
long-term acute care facilities or sub acute care facilities obviously this is
going to be big time if there's colonization or there's contact in other
words very poor hand-washing then that goes along with the environment again
risk factors antibiotics HIV hemodialysis casts so catheters these
Quinton catheters long-term acute care facilities colonization contact
environment so I think you've know and understand a little bit about what Mrs a
is where it comes from it's basically staph aureus it's basically a resistant
strain you know what the protein is it's a penicillin binding protein it comes
from the MEK a gene there are different variants factors which makes
community-acquired mrs a much worse than the run-of-the-mill hospital-acquired
pneumonia in fact let's look at a survival curve and I'll distinguish that
that'll make it very clear between these two okay so let's draw a graph here
let's look at survival so on this we're looking at survival and
here we're looking at days post admission and let's say in the blue
we're going to look at those that are the pant on Valentine leuco side and
toxin negative so that would be like your basically your hospital-acquired m
RSA and then we can also look at the yellow which is the pant on valentine
leukocidin toxin positive community-acquired mrs a so in terms of
that the survival was pretty poor basically going down here and lever
leveling out at about 30% whereas the survival for the hospital-acquired one
and again this is kind of blurring was a little bit more like this in terms of
the survival as you can see here in this situation you can see clearly that the
survival is much worse in the community acquired one because of that that toxin
so next let's talk a little bit of some of the manifestations of mrs a pneumonia
and staff pneumonia particularly and and what we could see
you