00:00
Let's ask some question
about our aminogylcosides.
00:04
The following is true
about aminoglycosides.
00:07
A) Aminoglycosides bind to
the 30 S subunit
of the bacterial ribosome.
00:14
B) Aminoglycosides have
no cell wall activity.
00:18
C) Gentamicin and tobramicin
are associate with vestibular
ototoxicity.
00:25
Amikacin and kanamycin are
associated with auditory
ototoxicity.
00:31
and D) All of the above is true.
00:34
And the right answer is
all of the above is true.
00:38
Let's do another question
a girl with a red rash.
00:42
A 12 year old woman has severe
staphylococcal skin infection
after a motor vehicle accident.
00:48
She is intubated and ventilated
in the intensive care unit.
00:53
She was started on an
intravenous vancomycin drip.
00:56
She develops a body wide
rash without wheals.
01:00
Her core temperature has
climbed to 37.9 degrees Celsius.
01:04
Her blood pressure is 112/77.
01:07
Her heart rate is a 109 beats per minute.
01:10
Her white count is 23.
01:13
What is happening
to this patient?
A) She has a leukemic rash;
the patient has had
a progression of her undiagnosed leukemia with a leukemic rash.
01:23
B) Severe renal failure due to
acute tubular necrosis,
with a uremic rash.
01:29
C) Septic shock;
the septic meningitis is
now a global sepsis with severe
peripheral vasodilation.
01:38
Or D) She has developed
a cutaneous reaction
due to the vancomycin.
01:43
Which is the right answer?
Good, she has developed
a cutaneous reaction.
01:52
So although a leukemic
rash is a possibility.
01:54
She does not fit the clinical
picture.
01:56
And it seems kind of
an unlikely diagnosis.
01:59
Acute tubular necrosis is not a
common reaction to vancomycin.
02:03
Sepsis is certainly an important
consideration and your major
differential diagnosis here.
02:08
But her heart rate is within
acceptable limits for a child
in intensive care unit.
02:13
And the blood pressure is
actually pretty normal.
02:15
She would have a much lower
blood pressure
if she were septic.
02:19
The correct answer
is going to be D.
02:22
She is having an acute reaction
called "Red Man Syndrome",
a well known side effect
of high dose vancomycin.
02:31
Let's pick the true statement.
02:34
A. Tetracyclines are broad spectrum antibiotics that bind
to the 50 S subunit
of the bacterial ribosome.
02:41
B. Aminoglycosides are broad spectrum antibiotics that bind
to the 50 S subunit
of the bacterial ribosome.
02:50
and C. Macrolides are broad spectrum antibiotics that bind
to the 50 S subunit
of the bacterial ribosome.
03:01
Good.
03:03
Macrolides are broad spectrum
antibiotics that bind to
the 50 S subunit
of the bacterial ribosome.
03:08
So remember tetracyclines
and aminoglycosides bind to
the 30 S subunit.
03:18
Let's take a look at penicillin.
03:20
Penicillin acts through
the following mechanism.
03:23
A) Reduction of calmodulin
B) Increasing beta-lactamase
activity
C) Inhibiting beta-lactamase
activity
D) Inhibiting the cross linking of peptidoglycan molecules
or E) Substitution
of the alanine terminal
for the lactate terminal.
03:45
The answer is D.
03:46
Inhibiting the cross linking
of peptidoglycan molecules.
03:52
Calmodulin has nothing
to do with antibiotics.
03:55
Beta-lactamase activity is how
bacteria becomes resistant to
penicillin.
04:00
Substitution of the alanine
terminal for lactate terminal
is how organisms are
thought to become resistant to
vancomycin.
04:07
Doesn't have anything to
do with penicillin per say.
04:11
Let's do another
question on septicemia.
04:14
So a patient has had a known
allergy to penicillin five
years ago, with a severe rash and low blood pressure.
04:21
Which of the following
medications would be
appropriate for use in a
gram-negative septicemia?
Would it be
A) Cefotetan
B) Amoxicillin
C) Amoxicillin-clavulonate
D) Methicillin
or E) Aztreonam
Good job, you picked E.
04:49
So amoxicillin will probably
will have a cross allergy with
penicillin as it is so
similar structurally.
04:56
Methicillin is
also a penicillin.
04:58
May also have a cross-allergy.
05:00
Cefotetan is a cephalosporin
and has lower likelihood of
cross allergy and maybe a
reasonable choice if it work
for the fact that we have
another choice on the list.
05:11
Cefotetan is otherwise excellent
at gram negative infections,
particularly septicemia.
05:18
Aztreonam is an antibiotic with no penicillin cross allergy.
05:23
And the answer is E.
05:24
Now the reason why we have this
question here is to reference
the lack of cross allergy
of aztreonam with penicillin
as a learning point, okay.
05:36
The following statements are
true about vancomycin except:
Vancomycin is not easily
absorbed when taken orally.
05:47
It is effective for
treating bowel infections.
05:51
B. Vancomycin does partially
penetrate the blood-brain barrier
allowing it to be an efficaceous
treatment for septic meningitis.
05:59
C.Vancomycin is an effective
agent against staphylococci,
although recently resistant strains have
been implicated in hospital breakouts.
06:07
And D.
06:08
Vancomycin is a broad spectrum antibiotic.
06:13
The answer is D.
06:15
So this is an incorrect response.
06:19
So it's the correct answer.
06:20
Remember we're asking which are true
EXCEPT, so the other three are true.
06:25
So vancomycin is a large, polar molecule
that does not easily cross barriers.
06:31
The transmembrane pores do not commonly let
vancomycin across because it's such a big molecule.
06:37
Now we take advantage of this characteristic to use
it against certain infections like bowel infections
as it tends to stay in the bowel and act
directly on organisms trapped in the bowel.
06:47
It is not known for crossing the blood brain barrier.
06:50
So a lot of times we may use
intrathecal administration
in cases of very severe meningitis
with responsive organisms.
06:59
Now do not mistake its incredible
effectiveness against gram positive bacteria
as being a broad spectrum agent.
07:08
A broad spectrum agent is one that cross the gram
positive, gram negative, anaerobe sort of barriers.
07:14
Whereas vancomycin is really a gram
positive agent in it's truer sense.
07:22
There you have it.
07:23
We covered a very large topic.
07:24
I know you're going to do well in your exams.
07:27
Show them what you know.