Download Anti-biotic Resistance

Evolution in Everyday Life
• The evolution of pesticide resistance in
insects.
• The evolution of herbicide resistance in
weeds.
• The evolution of antibiotic resistance in
bacteria.
• The evolution of drug resistance in viruses.
1
Charles Lyell was
A)A contemporary of Darwin.
B)A dynamical geologist.
C)An important influence on Darwin’s
thinking about how to study biology.
D)The captain of the Beagle on Darwin’s
voyage.
E)All of the above except (D).
2
The concept that a weak force over a long
period of time can have an effect comparable
to that of a stronger force in a much shorter
period of time is called:
A)Gradualism.
B) Adaptation.
C) Uniformitarianism.
D)Superposition.
E) Transmutation.
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Referring to the Figure above, rank the species pairs (1,2), (2,3), (3,4)
from least similar to most similar according to Darwin:
A) (1,2) least < (2,3) < (3,4) most.
B) (2,3) least < (3,4) < (1,2) most.
C) (1,2) least < (3,4) < (2,3) most.
D) (3,4) least < (1,2) < (2,3) most.
E) (3,4) least < (2,3) < (1,2) most.
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(1,2)
(2,3)
Dots are
Most Recent
Common
Ancestors
(3,4)
Referring to the Figure above, rank the species pairs (1,2), (2,3), (3,4)
from least similar to most similar according to Darwin:
A) (1,2) < (2,3) < (3,4).
B) (2,3) < (3,4) < (1,2).
C) (1,2) < (3,4) < (2,3).
D) (3,4) < (1,2) < (2,3).
E) (3,4) < (2,3) < (1,2).
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Evolution of Penicillin Resistance by
Bacteria
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Penicillin discovered in 1896, rediscovered by
Fleming in 1928.
Mass-production of penicillin began in 1943.
Staphylococcus aureus, is usually a harmless
passenger in the human body, but it can cause
pneumonia, toxic shock syndrome, the most
common cause of food poisoning.
The first penicillin-resistant strains of “Staph”
were isolated in 1947!
1967, penicillin-resistant Streptococcus
pneumoniae and gonorrhea
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The First Antibiotic: Penicillin
How Penicillin Kills Bacteria: penicillin
attaches to the cell walls of bacteria and
destroys a key molecular component of the
cell wall. With its cell wall disrupted, the
bacterium dies.
Resistant bacteria are not killed by
penicillin, they have genes which:
(1) alter cell walls to prevent binding
by penicillin
or
(2) produce enzymes that attack the
antibiotic: degrade the penicillin.
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Staphylococcus aureus is commonly carried on the skin of scalp,
arm pit, groin or in the nose of healthy people,
and sometimes in canned mushrooms on pizza. It is the most
common cause of food poisoning.
Common name: the “flesh-eating bacterium.”
Staph grows and reproduces from 50 0F to 120 0F, with the most
rapid growth occurring near human body temperature (about 98 0F).
MRSA commonly occurs in the hospital setting
but, more recently community-associated MRSA (CA-MRSA)
has been found in correctional facilities and athletic teams.
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Geometric Population Growth
CA-MRSA cases ranged from 0 to 9 per year from 1990 through 1999
and then increased exponentially from 36 in 2000 to 459 in 2003
459
Number of Cases
Of CA-MRSA
36
9
1999
2003
Time in Years
N2003 = b4 N1999
439= b4 (9) implies that b = 2.64!
Finite Resource: Humans! 6,000,0000,000
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Hospital Acquired or Nocosomial infections
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1983, resistant Enterococcus faecium, hospitalacquired intestinal infection.
in 1992, 13,300 hospital patients died of antibioticresistant bacterial infections
cost of treating hospital infections is $1-3 billion/yr
Patients with noscomial bacteremia spend
$3,600 more in direct hospital costs, and remain in
hospital 14 days longer than uninfected patients.
500,000 patients in American hospitals contract a
staphylococcal infection each year. 80+% of these
are penicillin resistant.
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> 50%
Methicillin
is the antibiotic
that replaced
Penicillin in
1975.
99
03
> 80%
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Vancomycin the drug of last defense
In 1992: 13,300 hospital patients died of antibioticresistant bacterial infections.
For more than a decade, scientists have been dreading
but expecting -- an S. aureus strain to emerge
that is resistant to vancomycin.
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Percentage of hospital Staphylococcus
That are multi-drug resistant
100%
"It's a serious threat now, and it's getting worse fast. “
50%
0%
Fiji
Belgium
USA
Japan
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The “Cost of Resistance”
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There is a life history trade-off for bacteria
between Anti-biotic Resistance and
Reproductive Capacity in the absence of
antibiotics.
The bacteria live in 2 Environments:
(1) The normal environment with a low
level of natural antibiotics produced by
competing molds;
(2) The hospital, doctor’s office, or animal
feed lot environment containing enormous
amounts of man-made antibiotics.
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What is a Life-History Trade-Off?
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It is based on the concept that an organism
cannot do everything well.
Football players vs Basketball Players: trade-off
between explosive strength (Football) and
aerobic endurance (basketball) involving
different kinds of muscle and physiology.
“Party”students vs “Serious” students: trade-off
between fun and study as a result of finite
amount of time.
Growth vs Reproduction: trade-off between
acquiring resources for growth and expending
resources for reproduction.
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Evolution in Two Environments
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Two kinds of bacteria:
(1) ABS, Anti-Biotic Sensitive
(2) ABR, Anti-Biotic Resistant
These bacteria live in 2 Environments:
(1) The normal environment low level of
antibiotics produced by competing molds;
(2) The hospital, doctor’s office, animal
feed lot: environments with vast
amounts of man-made antibiotics.
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The Cost of Resistance: a Life History
Trade-Off for the bacterium
In the normal environment, E1
ABS, Anti-Biotic Sensitive bacteria grow
faster than ABR, Anti-Biotic Resistant
bacteria because:
reproductive capacity: bABS > bABR
In the environments with antibiotics, E2:
ABR, Anti-Biotic Resistant bacteria grow
faster than ABS, Anti-Biotic Sensitive
bacteria because:
reproductive capacity:
bABR > bABS
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Trade-off in Population Growth
Normal Environment,
No Antibiotics:
Nt
Antibiotic Environment:
Nt
Time in Generations
bABS > bABR
Time in Generations
bABR > bABS
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b,
Reproductive Capacity
Trade-off = X
AB-Sensitive
High
AB-Resistant
Low
Anti-biotics
No Anti-biotics
Environments
ABR strains
Out grow
ABS strains
ABS strains
Out grow
ABR strains
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Use of Antibiotics Uncommon Before 1950
Anti-Biotic Resistance: favored only in the common environment,
selected against everywhere else. Hence, there is a
High frequency of anti-biotic resistant bacteria in 2006.
bABR > bABS
Rare Environment
in 1950:
Anti-biotics present
ABR strains favored
bABS > bABR
Common Environment
in 1950:
No anti-biotics
ABS strains favored
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Antibiotics Common After 1950
Anti-Biotic Sensitive: favored only in the rare environment,
selected against everywhere else. Hence, there is a
low frequency of anti-biotic sensitive bacteria.
bABR > bABS
bABS > bABR
Rare Environment
in 2006:
Anti-biotics Absent
ABS strains favored
Common Environment
in 2006:
Lots of anti-biotics
ABR strains favored
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Change in Use of Antibiotics = Change in the
Frequency of the 2 Environments
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Anti-biotic Environments were Rare Before 1950
but became Common After 1970
1985: 6 million antibiotic prescriptions for
sinusitis, Streptococcus pneumoniae and
Haemophilus influenzae common upper respiratory
tract bacterial species
1992: 13 million prescriptions for sinusitis
1985: 15 million prescriptions for middle ear
infections, Streptococcus pneumoniae bacteria
1992: 23.6 million prescriptions for middle ear
infections
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Feedlot Use of Antibiotics
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19 million pounds of antibiotics per year are fed to
farm animals, and 88 percent of that amount was fed
at low doses, which favor evolution of antibiotic
resistance because they do not kill all bacteria in a
colony.
36 million antibiotic prescriptions at 1.5 grams per
prescription.
(36 million scripts) (1.5 g) = 54 million grams
8.6 trillion grams in feedlots vs 54 million grams in
prescriptions
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Man-made alteration of the environment by industrial pollution
changes natural selection on white and black color morphs of
the moth, Biston betularia.
Man-made alteration of the environment by use of antibiotics to
combat disease in humans and domestic animals changes
natural selection on sensitive and resistant morphs of
Staphylococcus aureus
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Environmental Variation and Genetic Trade-offs
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Together, environmental variation and a
genetic trade-off means that more than one
genetic kind of individual will be maintained
in the population.
More than one environment, More than one
Genetic Strategy for Survival.
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