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Antibiotic Resistance & MRSA
1. Recall how mutations can lead to
antibiotic resistance (LAST LESSON).
2. Describe how resistance can be passed
on through both vertical and horizontal
gene transmission.
3. Describe how antibiotic resistance has
made it difficult to treat diseases such as
Tuberculosis and MRSA.…read more

Slide 2

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1. What is an antibiotic?
2. How do antibiotics work?
3. How do some microbes become resistant
to antibiotics?
4. Explain why resistance in microbes is an
example of natural selection.…read more

Slide 3

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1. Antibiotics are chemicals that either kill or inhibit the growth
of bacteria / fungi.
2. Antibiotics interfere with essential processes in bacterial
cells e.g. cell wall formation, DNA replication etc.
3. Mutations change the base sequence of DNA, this may alter
the structure of the protein targeted by the antibiotic,
preventing it from working.
4. Resistance is clearly an example of natural selection
because a useful characteristic (resistance) is selected for,
becoming more frequent in a population.
· Variation ­ some bacteria have alleles for resistance some don't.
· Selective pressure ­ the antibiotic kills any without resistance alleles.
· Inheritance ­ resistant bacteria survive and reproduce.
· Time ­ after time, most bacteria in the population will carry the
resistance allele.…read more

Slide 4

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RECAP: Evolution of antibiotic resistance
Variation Pressure Heredity Time…read more

Slide 5

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The problem of antibiotic resistance (news)
The problem of antibiotic resistance (news)…read more

Slide 6

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Why has antibiotic resistance become
an increasing problem?
· Increasing use of antibiotics;
· Increased exposure of bacteria to antibiotics;
· Patients frequently fail to complete their course
of antibiotics;
· Any bacteria with mutations that confer
resistance survive; those without resistance do
not survive;
· Removal of competitors allows rapid increase in
number of resistant bacteria;
· Antibiotics ineffective against resistant strains…read more

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