Development of antibiotic resistant
Staphylococcus aureus over time
Attacks and Defenses Course
University of Vermont Coll...
About
This is a presentation that I made my senior year in medical
school for an infectious disease course at the Universi...
About
This is a presentation that I made my senior year in medical
school for an infectious disease course at the Universi...
Once upon a time there was a bacterium. All of his bacteria friends
thought he was pretty good looking.
Once upon a time there was a bacterium. All of his bacteria friends
thought he was pretty good looking.
They would comment on how nice his gold color was.
Once upon a time there was a bacterium. All of his bacteria friends
tho...
Once upon a time there was a bacterium. All of his bacteria friends
thought he was pretty good looking.
And because of tha...
Here’s staph aureus’ nice thick peptidoglycan wall!
Here he is in his towel returning from the Gram Stain water park!
His peptidoglycan layer got darkly stained.
Look! He’s all purple! That’s why he’s called gram positive.
Here he is in his towel returning from the Gram Stain water p...
Staph aureus likes to live on your body
with his friends. The best way is in
clusters!
Skin!
In your
nares!
He has a kitty named Catalase.
Catalase is a little strange
as she only eats hydrogen peroxide
H2O2
H2O2
and only pees out H2O and O2.
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
H2O2
O2
H2O2
O2
Good kitty.
One day, staph aureus went for a hike and came across some
fungus. It was called Penicillum.
As he got close, he started feeling funny.
Lets find out why…
O COOH
R
membrane
Peptidoglycan layer
O COOH
R
Penicillin!
Transpeptidase
(penicillin binding protein)
membrane
Peptidoglycan layer
O COOH
R
Penicillin!
membrane
Peptidoglycan layer
O COOH
R
Penicillin!
membrane
Peptidoglycan layer
O COOH
R
Penicillin!
membrane
Peptidoglycan layer
O COOH
R
Penicillin!
membrane
O COOH
R
Penicillin!
And then he died.
But for other staph aureus bacteria, this wasn’t much of a problem
because they didn’t run into penicillium when they were...
Sometimes they had a little too much fun and would cause infections
Like crusty superficial
infections of the skin in
kids...
Sometimes they would hang out in food and release cytolytic toxins that
make people sick.
Food
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellular matrix, hya...
hyaluronidase
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellul...
hyaluronidase
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellul...
hyaluronidase
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellul...
hyaluronidase
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellul...
hyaluronidase
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellul...
hyaluronidase
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellul...
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellular matrix, hya...
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellular matrix, hya...
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellular matrix, hya...
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellular matrix, hya...
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellular matrix, hya...
Or would sneak into places where they shouldn’t by breaking down a
component of collagen and the extracellular matrix, hya...
He was very good at hide and seek whenever red
blood cells were around.
He’d just release coagulase and they form a clot around him
And with just a little staphylokinase, the clot would break up!
And then just for fun, he’d blow up the red blood cells.
And then just for fun, he’d blow up the red blood cells.
And then just for fun, he’d blow up the red blood cells.
And then just for fun, he’d blow up the red blood cells.
Researchers one day would find that he and his friends strep
pyogenes and strep agalactidae did this so well on a blood
ag...
Beta’s the best!
Researchers one day would find that he and his friends strep
pyogenes and strep agalactidae did this so w...
Every once and a while a white blood
cell would try to pick on him
And would try to eat him
But he’d prevent being phagocytosed
With his nice polysaccharide slime
layer and protein-A on his surface.
Then he’d blow up the white blood
cell with leukocidin!
Then he’d blow up the white blood
cell with leukocidin!
Then he’d blow up the white blood
cell with leukocidin!
Then he’d blow up the white blood
cell with leukocidin!
Then he’d blow up the white blood
cell with leukocidin!
Then he’d blow up the white blood
cell with leukocidin!
T
S
S
When he was feeling really
mean, he’d release a
superantigen toxin
T
S
S
When he was feeling really
mean, he’d release a
superantigen toxin
Like TSS-1 and cause toxic
shock syndrome!
When he was feeling really
mean, he’d release a
superantigen toxin
Like TSS-1 and cause toxic
shock syndrome!
All of the l...
When he was feeling really
mean, he’d release a
superantigen toxin
Like TSS-1 and cause toxic
shock syndrome!
All of the l...
When he was feeling really
mean, he’d release a
superantigen toxin
And people would get fever,
low blood pressure, and a
b...
But all in all, as long as he stayed
away from the Penicillum fungus,
there wasn’t too much to worry
about!
Until one day when he was
innocently hanging out in a joint
having a bit of fun…
Until one day when he was
innocently hanging out in a joint
having a bit of fun…
When he started feeling funny.
And he died.
But not just him! His friend
causing endocarditis died!
And his friend causing cellulitis died!
And his friends causing impetigo died!
How could this be?
Penicillin!
How could this be?
Penicillin!
How could this be?
It seems someone figured out
how to extract the active
compound from the penicillum
fungus ...
So now staph aureus was dying left and right! Anytime
they got out of control, they were taken down with
some penicillin.
Until one day...
Until one day...
Until one day…
One staph aureus didn’t seem
bothered by the penicillin!
Let’s see why…
Well those are new!
What do they do?
membrane
Peptidoglycan layer
O
Uh oh, here comes Penicillin!
membrane
Peptidoglycan layer
O
What’s going on here?
membrane
Peptidoglycan layer
O
The beta lactam ring is
broken! This is a beta-
lactamase.
membrane
Peptidoglycan layer
O
membrane
Peptidoglycan layer
O
membrane
Peptidoglycan layer
And since the lactamase has been
used, more is produced.
membrane
Peptidoglycan layer
And since the lactamase has been
used, more is produced.
membrane
Peptidoglycan layer
And since the lactamase has been
used, more is produced.
So this little staph aureus
is resistant to beta lactam
drugs like penicillin and
amoxicillin!
But what about the others?
aah
aah-CHOO!
A virus that infects bacteria, a bacteriophage!
A virus that infects bacteria, a bacteriophage!
And it’s injecting its genome.
A virus that infects bacteria, a bacteriophage!
And it’s injecting its genome.
Along with the beta-
lactamase gene from th...
Now he’s resistant too!
And pretty soon the
bacteriophage spread the
resistance to almost all of the
staph aureus all over the
developed world!
Resistant staph aureus can be
around with penicillum without
worry.
Resistant staph aureus can be
around with penicillum without
worry.
He lives wherever he pleases!
The penicillin does noth...
Until one day…
Until one day…
What happened?
membrane O COOH
membrane O COOH
membrane O COOH
membrane
O
COOH
membrane
O
COOH
It’s clavulanate, a beta lactamase inhibitor!
membrane
O
COOH
It’s clavulanate, a beta lactamase inhibitor!
It destroys the beta lactamase with its
suicide beta lactam ...
membrane
O
COOH
It destroys the beta lactamase with its
suicide beta lactam ring. It does not
trigger increased production...
membrane
O
COOH
It destroys the beta lactamase with its
suicide beta lactam ring. It does not
trigger increased production...
O
COOH
It destroys the beta lactamase with its
suicide beta lactam ring. It does not
trigger increased production of beta
...
But as long as there are no beta-lactamase inhibitors, they’ll still be
resistant to beta-lactam antibiotics, right?
Wrong.
But as long as there are no beta-lactamase inhibitors, they’ll still be
resistant to beta-lactam antibiotics, right?
membrane
O COOH
What’s this? It looks like penicillin
except with a funny new side chain.
membrane
O COOH
What’s this? It looks like penicillin
except with a funny new side chain.
It’s a synthetic penicillin, met...
membrane
O COOH
What’s this? It looks like penicillin
except with a funny new side chain.
It’s a synthetic penicillin, met...
membrane
O COOH
What’s this? It looks like penicillin
except with a funny new side chain.
It’s a synthetic penicillin, met...
membrane
O COOH
What’s this? It looks like penicillin
except with a funny new side chain.
And now the beta lactamase can’t...
membrane
O COOH
What’s this? It looks like penicillin
except with a funny new side chain.
It’s a synthetic penicillin, met...
O COOH
What’s this? It looks like penicillin
except with a funny new side chain.
It’s a synthetic penicillin, methicillin ...
This staph aureus was taken out by a different drug entirely!
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
It has one more carbo...
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
Along with its hydrog...
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
It has one more carbo...
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
It has one more carbo...
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
It has one more carbo...
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
It has one more carbo...
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
It has one more carbo...
membrane
O COOH
Look! A celphalosporin! It’s a new drug with
the structure of a penicillin except...
It has one more carbo...
O COOH
The beta lactamase no longer fits. The cephalosporin
will chop up the wall just like penicillin!
Look! A celphalosp...
Over time some staph aureus bacteria have developed new things
like the beta lactamases
that will chop up
synthetic penici...
Over time some staph aureus bacteria have developed new things
like the beta lactamases
that will chop up
synthetic penici...
So researchers will add more
modifications to make the bacterial
weaponry no longer work.
O COO
O COO
And bacteria will again come up
with ways to chop up these drugs.
And so on.
O COO
O COO
After a long enough time, one particular staph aureus underwent a
very strange mutation.
After a long enough time, one particular staph aureus underwent a
very strange mutation.
After a long enough time, one particular staph aureus underwent a
very strange mutation.
Let’s take a closer look…
After a long enough time, one particular staph aureus underwent a
very strange mutation.
membrane
It looks like the transpeptidase, also known as the
penicillin binding protein, has changed!
membrane
It looks like the transpeptidase, also known as the
penicillin binding protein, has changed!
O
O COOH
Now cephalo...
membrane
It looks like the transpeptidase, also known as the
penicillin binding protein, has changed!
O
O COOH
Now cephalo...
If we were to look at his DNA, we’d find that he
has something called the MecA gene.
DNA
MecA
It means that all of his off...
If we were to look at his DNA, we’d find that he
has something called the MecA gene.
It means that all of his offspring wi...
If we were to look at his DNA, we’d find that he
has something called the MecA gene.
It means that all of his offspring wi...
If we were to look at his DNA, we’d find that he
has something called the MecA gene.
It means that all of his offspring wi...
But the MecA gene slows him down!
He’ll be outgrown every time by plain-old methicillin
susceptible staph aureus (MSSA).
But the MecA gene slows him down!
He’ll be outgrown every time by plain-old methicillin
susceptible staph aureus (MSSA).
But the MecA gene slows him down!
He’ll be outgrown every time by plain-old methicillin
susceptible staph aureus (MSSA).
O
O COOH
O
O COOH
Unless there are antibiotics like methicillin or
cephalosporins around.
Just for that reason, MRSA loves to live in hospitals!
So if people are in the hospital for long enough, they’ll often get
colonized by MRSA. For that, he is known as hospital-a...
But as soon after they get home, they get recolonized by MSSA.
And up until recently HA-MRSA stayed in and around hospitals.
And up until recently HA-MRSA stayed in and around hospitals.
Until one day…
And up until recently HA-MRSA stayed in and around hospitals.
Until one day…
DNA
MecA
One particular MRSA developed a smaller and
more efficient MecA gene.
And can now compete with MSSA out in the community.
And can now compete with MSSA out in the community.
And can now compete with MSSA out in the community.
O
O COOH
O
O COOH
But is still resistant to the beta lactam drugs!
Now a good amount of the population in the community is
colonized with this new, competitive MRSA, known as community-
acq...
Now a good amount of the population in the community is
colonized with this new, competitive MRSA, known as community-
acq...
One thing’s for sure, Staph aureus and Catalase will be around for a long, long time.
The end.
One thing’s for sure, Staph aureus and Catalase will be around for a long, long time.
Development of resistant Staphylococcus aureus over time
Development of resistant Staphylococcus aureus over time
Development of resistant Staphylococcus aureus over time
Development of resistant Staphylococcus aureus over time
Development of resistant Staphylococcus aureus over time
Development of resistant Staphylococcus aureus over time
Development of resistant Staphylococcus aureus over time
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Development of resistant Staphylococcus aureus over time

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A module covering the development of antibiotic resistance in Staphylococcus aureus including the development of MRSA or methicillin resistant staph aureus.

Published in: Health & Medicine

Development of resistant Staphylococcus aureus over time

  1. Development of antibiotic resistant Staphylococcus aureus over time Attacks and Defenses Course University of Vermont College of Medicine January 2011 Timothy Plante, MS-IV
  2. About This is a presentation that I made my senior year in medical school for an infectious disease course at the University of Vermont College of Medicine. It was picked up by BoingBoing.net and was viewed by quite a few folks on the internet.
  3. About This is a presentation that I made my senior year in medical school for an infectious disease course at the University of Vermont College of Medicine. It was picked up by BoingBoing.net and was viewed by quite a few folks on the internet. I had a lot of fun making this. Enjoy!
  4. Once upon a time there was a bacterium. All of his bacteria friends thought he was pretty good looking.
  5. Once upon a time there was a bacterium. All of his bacteria friends thought he was pretty good looking.
  6. They would comment on how nice his gold color was. Once upon a time there was a bacterium. All of his bacteria friends thought he was pretty good looking.
  7. Once upon a time there was a bacterium. All of his bacteria friends thought he was pretty good looking. And because of that, he was named staph aureus as auro is the Latin word for gold. They would comment on how nice his gold color was.
  8. Here’s staph aureus’ nice thick peptidoglycan wall!
  9. Here he is in his towel returning from the Gram Stain water park! His peptidoglycan layer got darkly stained.
  10. Look! He’s all purple! That’s why he’s called gram positive. Here he is in his towel returning from the Gram Stain water park! His peptidoglycan layer got darkly stained.
  11. Staph aureus likes to live on your body with his friends. The best way is in clusters! Skin! In your nares!
  12. He has a kitty named Catalase.
  13. Catalase is a little strange
  14. as she only eats hydrogen peroxide H2O2
  15. H2O2
  16. and only pees out H2O and O2. H2O2
  17. H2O2
  18. H2O2
  19. H2O2
  20. H2O2
  21. H2O2
  22. H2O2
  23. H2O2
  24. H2O2
  25. H2O2
  26. H2O2
  27. H2O2 O2
  28. H2O2 O2 Good kitty.
  29. One day, staph aureus went for a hike and came across some fungus. It was called Penicillum.
  30. As he got close, he started feeling funny. Lets find out why…
  31. O COOH R
  32. membrane Peptidoglycan layer O COOH R Penicillin! Transpeptidase (penicillin binding protein)
  33. membrane Peptidoglycan layer O COOH R Penicillin!
  34. membrane Peptidoglycan layer O COOH R Penicillin!
  35. membrane Peptidoglycan layer O COOH R Penicillin!
  36. membrane Peptidoglycan layer O COOH R Penicillin!
  37. membrane O COOH R Penicillin!
  38. And then he died.
  39. But for other staph aureus bacteria, this wasn’t much of a problem because they didn’t run into penicillium when they were hanging out in the skin or nares. They had a pretty fun life!
  40. Sometimes they had a little too much fun and would cause infections Like crusty superficial infections of the skin in kids called impetigo
  41. Sometimes they would hang out in food and release cytolytic toxins that make people sick. Food
  42. Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  43. hyaluronidase Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  44. hyaluronidase Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  45. hyaluronidase Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  46. hyaluronidase Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  47. hyaluronidase Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  48. hyaluronidase Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  49. Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  50. Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  51. Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  52. Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  53. Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  54. Or would sneak into places where they shouldn’t by breaking down a component of collagen and the extracellular matrix, hyaluronic acid, with hyaluronidase!
  55. He was very good at hide and seek whenever red blood cells were around.
  56. He’d just release coagulase and they form a clot around him
  57. And with just a little staphylokinase, the clot would break up!
  58. And then just for fun, he’d blow up the red blood cells.
  59. And then just for fun, he’d blow up the red blood cells.
  60. And then just for fun, he’d blow up the red blood cells.
  61. And then just for fun, he’d blow up the red blood cells.
  62. Researchers one day would find that he and his friends strep pyogenes and strep agalactidae did this so well on a blood agar plate that they would be able to be identified by their complete hemolysis, a pattern we call beta hemolysis!
  63. Beta’s the best! Researchers one day would find that he and his friends strep pyogenes and strep agalactidae did this so well on a blood agar plate that they would be able to be identified by their complete hemolysis, a pattern we call beta hemolysis!
  64. Every once and a while a white blood cell would try to pick on him
  65. And would try to eat him
  66. But he’d prevent being phagocytosed
  67. With his nice polysaccharide slime layer and protein-A on his surface.
  68. Then he’d blow up the white blood cell with leukocidin!
  69. Then he’d blow up the white blood cell with leukocidin!
  70. Then he’d blow up the white blood cell with leukocidin!
  71. Then he’d blow up the white blood cell with leukocidin!
  72. Then he’d blow up the white blood cell with leukocidin!
  73. Then he’d blow up the white blood cell with leukocidin!
  74. T S S When he was feeling really mean, he’d release a superantigen toxin T S S
  75. When he was feeling really mean, he’d release a superantigen toxin Like TSS-1 and cause toxic shock syndrome!
  76. When he was feeling really mean, he’d release a superantigen toxin Like TSS-1 and cause toxic shock syndrome! All of the lymphocytes would cause inflammation even though TSS-1 isn’t the antigen they’re supposed to react to!
  77. When he was feeling really mean, he’d release a superantigen toxin Like TSS-1 and cause toxic shock syndrome! All of the lymphocytes would cause inflammation even though TSS-1 isn’t the antigen they’re supposed to react to!
  78. When he was feeling really mean, he’d release a superantigen toxin And people would get fever, low blood pressure, and a blanching rash that looked like a sunburn! Like TSS-1 and cause toxic shock syndrome! All of the lymphocytes would cause inflammation even though TSS-1 isn’t the antigen they’re supposed to react to!
  79. But all in all, as long as he stayed away from the Penicillum fungus, there wasn’t too much to worry about!
  80. Until one day when he was innocently hanging out in a joint having a bit of fun…
  81. Until one day when he was innocently hanging out in a joint having a bit of fun… When he started feeling funny.
  82. And he died.
  83. But not just him! His friend causing endocarditis died!
  84. And his friend causing cellulitis died!
  85. And his friends causing impetigo died!
  86. How could this be?
  87. Penicillin! How could this be?
  88. Penicillin! How could this be? It seems someone figured out how to extract the active compound from the penicillum fungus and make it to a drug! O COOH R
  89. So now staph aureus was dying left and right! Anytime they got out of control, they were taken down with some penicillin.
  90. Until one day...
  91. Until one day...
  92. Until one day… One staph aureus didn’t seem bothered by the penicillin!
  93. Let’s see why…
  94. Well those are new! What do they do?
  95. membrane Peptidoglycan layer O Uh oh, here comes Penicillin!
  96. membrane Peptidoglycan layer O What’s going on here?
  97. membrane Peptidoglycan layer O The beta lactam ring is broken! This is a beta- lactamase.
  98. membrane Peptidoglycan layer O
  99. membrane Peptidoglycan layer O
  100. membrane Peptidoglycan layer And since the lactamase has been used, more is produced.
  101. membrane Peptidoglycan layer And since the lactamase has been used, more is produced.
  102. membrane Peptidoglycan layer And since the lactamase has been used, more is produced.
  103. So this little staph aureus is resistant to beta lactam drugs like penicillin and amoxicillin!
  104. But what about the others?
  105. aah
  106. aah-CHOO!
  107. A virus that infects bacteria, a bacteriophage!
  108. A virus that infects bacteria, a bacteriophage! And it’s injecting its genome.
  109. A virus that infects bacteria, a bacteriophage! And it’s injecting its genome. Along with the beta- lactamase gene from the resistant staph aureus!
  110. Now he’s resistant too!
  111. And pretty soon the bacteriophage spread the resistance to almost all of the staph aureus all over the developed world!
  112. Resistant staph aureus can be around with penicillum without worry.
  113. Resistant staph aureus can be around with penicillum without worry. He lives wherever he pleases! The penicillin does nothing anymore.
  114. Until one day…
  115. Until one day…
  116. What happened?
  117. membrane O COOH
  118. membrane O COOH
  119. membrane O COOH
  120. membrane O COOH
  121. membrane O COOH It’s clavulanate, a beta lactamase inhibitor!
  122. membrane O COOH It’s clavulanate, a beta lactamase inhibitor! It destroys the beta lactamase with its suicide beta lactam ring. It does not trigger increased production of beta lactamase!
  123. membrane O COOH It destroys the beta lactamase with its suicide beta lactam ring. It does not trigger increased production of beta lactamase! COOH And now a penicillin analogue like amoxicillin can come in and do its job. It’s clavulanate, a beta lactamase inhibitor!
  124. membrane O COOH It destroys the beta lactamase with its suicide beta lactam ring. It does not trigger increased production of beta lactamase! COOH And now a penicillin analogue like amoxicillin can come in and do its job. It’s clavulanate, a beta lactamase inhibitor!
  125. O COOH It destroys the beta lactamase with its suicide beta lactam ring. It does not trigger increased production of beta lactamase! COOH And now a penicillin analogue like amoxicillin can come in and do its job. It’s clavulanate, a beta lactamase inhibitor!
  126. But as long as there are no beta-lactamase inhibitors, they’ll still be resistant to beta-lactam antibiotics, right?
  127. Wrong. But as long as there are no beta-lactamase inhibitors, they’ll still be resistant to beta-lactam antibiotics, right?
  128. membrane O COOH What’s this? It looks like penicillin except with a funny new side chain.
  129. membrane O COOH What’s this? It looks like penicillin except with a funny new side chain. It’s a synthetic penicillin, methicillin (we learned about its cousin nafcillin in class).
  130. membrane O COOH What’s this? It looks like penicillin except with a funny new side chain. It’s a synthetic penicillin, methicillin (we learned about its cousin nafcillin in class).
  131. membrane O COOH What’s this? It looks like penicillin except with a funny new side chain. It’s a synthetic penicillin, methicillin (we learned about its cousin nafcillin in class).
  132. membrane O COOH What’s this? It looks like penicillin except with a funny new side chain. And now the beta lactamase can’t reach the beta lactam ring to do its job. It’s a synthetic penicillin, methicillin (we learned about its cousin nafcillin in class).
  133. membrane O COOH What’s this? It looks like penicillin except with a funny new side chain. It’s a synthetic penicillin, methicillin (we learned about its cousin nafcillin in class). And now the beta lactamase can’t reach the beta lactam ring to do its job.
  134. O COOH What’s this? It looks like penicillin except with a funny new side chain. It’s a synthetic penicillin, methicillin (we learned about its cousin nafcillin in class). And now the beta lactamase can’t reach the beta lactam ring to do its job.
  135. This staph aureus was taken out by a different drug entirely!
  136. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except...
  137. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... It has one more carbon. Look, a six- carbon ring!
  138. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... Along with its hydrogen atoms. It has one more carbon. Look, a six- carbon ring! HH
  139. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... It has one more carbon. Look, a six- carbon ring! HH Along with its hydrogen atoms.
  140. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... It has one more carbon. Look, a six- carbon ring! HH Along with its hydrogen atoms.
  141. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... It has one more carbon. Look, a six- carbon ring! The beta lactamase no longer fits. The cephalosporin will chop up the wall just like penicillin! HH Along with its hydrogen atoms.
  142. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... It has one more carbon. Look, a six- carbon ring! The beta lactamase no longer fits. The cephalosporin will chop up the wall just like penicillin! HH Along with its hydrogen atoms.
  143. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... It has one more carbon. Look, a six- carbon ring! The beta lactamase no longer fits. The cephalosporin will chop up the wall just like penicillin! Along with its hydrogen atoms.
  144. membrane O COOH Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... It has one more carbon. Look, a six- carbon ring! The beta lactamase no longer fits. The cephalosporin will chop up the wall just like penicillin! Along with its hydrogen atoms.
  145. O COOH The beta lactamase no longer fits. The cephalosporin will chop up the wall just like penicillin! Look! A celphalosporin! It’s a new drug with the structure of a penicillin except... It has one more carbon. Look, a six- carbon ring! Along with its hydrogen atoms.
  146. Over time some staph aureus bacteria have developed new things like the beta lactamases that will chop up synthetic penicillins like methicillin or nafcillin O COO
  147. Over time some staph aureus bacteria have developed new things like the beta lactamases that will chop up synthetic penicillins like methicillin or nafcillin or the cephalosporins. O COO O COO
  148. So researchers will add more modifications to make the bacterial weaponry no longer work. O COO O COO
  149. And bacteria will again come up with ways to chop up these drugs. And so on. O COO O COO
  150. After a long enough time, one particular staph aureus underwent a very strange mutation.
  151. After a long enough time, one particular staph aureus underwent a very strange mutation.
  152. After a long enough time, one particular staph aureus underwent a very strange mutation.
  153. Let’s take a closer look… After a long enough time, one particular staph aureus underwent a very strange mutation.
  154. membrane It looks like the transpeptidase, also known as the penicillin binding protein, has changed!
  155. membrane It looks like the transpeptidase, also known as the penicillin binding protein, has changed! O O COOH Now cephalosporins and synthetic penicillins like methicillin have nothing to attack.
  156. membrane It looks like the transpeptidase, also known as the penicillin binding protein, has changed! O O COOH Now cephalosporins and synthetic penicillins like methicillin have nothing to attack. And because of that, it’s a methicillin resistant staph aureus or MRSA.
  157. If we were to look at his DNA, we’d find that he has something called the MecA gene. DNA MecA It means that all of his offspring will also have this gene.
  158. If we were to look at his DNA, we’d find that he has something called the MecA gene. It means that all of his offspring will also have this gene.
  159. If we were to look at his DNA, we’d find that he has something called the MecA gene. It means that all of his offspring will also have this gene.
  160. If we were to look at his DNA, we’d find that he has something called the MecA gene. It means that all of his offspring will also have this gene.
  161. But the MecA gene slows him down! He’ll be outgrown every time by plain-old methicillin susceptible staph aureus (MSSA).
  162. But the MecA gene slows him down! He’ll be outgrown every time by plain-old methicillin susceptible staph aureus (MSSA).
  163. But the MecA gene slows him down! He’ll be outgrown every time by plain-old methicillin susceptible staph aureus (MSSA).
  164. O O COOH
  165. O O COOH Unless there are antibiotics like methicillin or cephalosporins around.
  166. Just for that reason, MRSA loves to live in hospitals!
  167. So if people are in the hospital for long enough, they’ll often get colonized by MRSA. For that, he is known as hospital-acquired MRSA (HA-MRSA).
  168. But as soon after they get home, they get recolonized by MSSA.
  169. And up until recently HA-MRSA stayed in and around hospitals.
  170. And up until recently HA-MRSA stayed in and around hospitals. Until one day…
  171. And up until recently HA-MRSA stayed in and around hospitals. Until one day…
  172. DNA MecA One particular MRSA developed a smaller and more efficient MecA gene.
  173. And can now compete with MSSA out in the community.
  174. And can now compete with MSSA out in the community.
  175. And can now compete with MSSA out in the community.
  176. O O COOH
  177. O O COOH But is still resistant to the beta lactam drugs!
  178. Now a good amount of the population in the community is colonized with this new, competitive MRSA, known as community- acquired MRSA (CA-MRSA).
  179. Now a good amount of the population in the community is colonized with this new, competitive MRSA, known as community- acquired MRSA (CA-MRSA). There are a few classes of other antibiotics out there which work on other bacterial targets to beat HA-MRSA and CA-MRSA. Resistance against these drugs is slowly but surely emerging.
  180. One thing’s for sure, Staph aureus and Catalase will be around for a long, long time.
  181. The end. One thing’s for sure, Staph aureus and Catalase will be around for a long, long time.

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