00:00
Right, so that's the discussion about community
acquired pneumonia which is commonest form
of pneumonia, and the one that most people
will be dealing with most of the time.
00:10
There are, as I've mentioned earlier,
other types of pneumonia, the hospital acquired,
the ventilator acquired, and there is the
immunosuppressed pneumonia. And the reason
why we define these as separate to community
acquired pneumonia is that the infecting organisms
are going to be different. The chance of having
a standard normal community acquired organism
is much lower in hospital acquired disease.
So for example hospital acquired pneumonia,
the common organism causing disease in those
circumstances will be Staphylococcus aureus,
and the gram-negative bacteria: Klebsiella,
E. coli Serratia and Pseudomonas aeruginosa,
and these organisms are harder to treat, and
do not respond to the standard amoxicillin
and macrolide therapy that you use for community
acquired pneumonia. So they require very specific
treatments. Immunosuppressed patients,
because of that
effects of having a very weak immune system,
suddenly the patient is actually exposed to
infection with a whole range of microorganisms
that don't normally affect people, and that
doesn't just include bacteria. The bacteria
will be the same as you might get it in a
hospital acquired disease, but in addition
there are a range of viruses, cytomegalovirusese
which may cause infection in these circumstances,
and cause severe disease. And in addition,
the respiratory viruses that in most people are
self-limiting and very mild disease parainfluenza,
adenovirus, etc. rhinovirus, cause much more
severe disease in the immunosuppressed patient.
01:36
And in addition, there is a range of organisms, fungi
which you may get infected with in the immunosuppressed
which would never normally infect somebody
who's got a normal immune system, and that's
mainly Aspergillus and Pneumocystis jirovecii.
So hospital acquired pneumonia is important
because actually it is the commonest fatal
hospital acquired infection. So you need to know
about this, as a disease that requires close
attention and aggressive treatment when it
develops. For treatment it needs to cover the
organisms as we discussed, Staphylococcus aureus,
the gram-negatives, and pseudomonas.
02:13
Empiric treatment with broad spectrum I.V. antibiotics is started while waiting for the results
of the sputum in blood cultures to guide specific therapy.
02:21
Things to consider include recent antibiotic therapy, comorbidities and likelihood of multiple Drug-Resistant or MDR pathogens.
02:30
This can be seen in the hospital antibiogram.
02:32
The initial antibiotic therapy depends on several factors. First, if there's a low risk for multiple Drug-Resistant pathogens,
piperacillin/tazobactam or cefepime can be used.
02:44
If there's a higher risk for multiple drug resistant Pseudomonas amikacin can be added to the regimen.
02:49
And finally, if there's a risk for resistant Pseudomonas and MRSA, you can add vancomycin or linezolid to the regimen.
02:57
Remember, the dosing needs to be adjusted based on the patient's renal function.
03:01
The actual presentation of hospital acquired pneumonia
is pretty much the same as community acquired
pneumonia, cough, fever, shortness of breath,
and with new consolidation, a rise in the
markers of inflammation. Pneumonia in
immunocompromised is very much
more complex than normal pneumonia because
of this extended range of organisms that may
be causing the problems. And again, just to
reiterate we are talking about patients who
have really quite marked immunosuppression.
They have had to have a organ or bone marrow
transplantation. They’ve been receiving
chemotherapy or high-dose cytotoxic agents
or biological agents to immunosuppress them
because of a major inflammatory disease such
as connective tissue disease, or they have
HIV infection with a low CD4 count, or they
have a hematological malignancy which by
their very nature affect the white cells and
therefore make you much more immunosuppressed
that you would be normally. The situation
here is that there is such a large range of
organisms, the decision about treatment options
is much more complex than it would be in a
normal person presented with a community acquired
pneumonia, because you may need to treat respiratory
viruses, you may need to treat cytomegalovirus,
you need to treat for the organisms that make
hospital acquired pneumonia, and then there
are the fungi, Aspergillus and Pneumocystis,
and unfortunately, Aspergillus and Pneumocystis
require very different treatments. So it is
a very complex situation that requires clinical
assessment to make sure the right medication
is given to the patient, and often these patients
will end up on antibacterials, antivirals, and
antifungal agents, because we are not quite
sure what's going on. This is a CT scan showing
what an invasive
fungal infection looks like after a stem cell
transplant with focal disease at the top of
the right lung.