Antibiotic Resistance

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Antibiotic Resistance

• Why Evolution is Important Now

2
What are Antibiotics?

• Chemicals that either kill or inhibit the growth
  of bacteria
• Naturally produced by bacteria and fungi
• Erythromycin produced by bacteria Streptomyces
  erythraeus
• Penicillin produced by fungi Penicillium
• Can be also artificially produced in the
  laboratory
• Sulfanilamide, Cipro completely synthetic
• Ampicillin, Amoxycillin natural products with
  chemical modification.

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How Antibiotics Work

• Prevent proper formation of the bacterial cell
  wall
• Cell wall normally prevents cell from bursting
  when excess water
• enters the cell if cell wall is damaged, cell
  bursts and dies
• Examples are penicillin, ampicillin,
  amoxycillin, vancomycin

• Disrupt protein synthesis or cell metabolism
• -Bind to ribosomes - disrupt process in various
  ways
• Examples are tetracycline, erythromycin,
  streptomycin, kanamycin
• -Block synthesis of needed metabolic chemicals
  e.g. folic acid
• Example is sulfanilamide

• Interfere with DNA synthesis
• Block replication of the bacterial chromosome
• Example is Cipro

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What Is Antibiotic Resistance?

• Antibiotic Resistance is when bacteria possess
  the ability to deactivate the action of
  antibiotics.

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What are the Mechanisms ofAntibiotic Resistance?

• Bacteria possess structures that prevent
  antibiotic
• from entering the cell (modify cell wall).
• Bacteria can pump antibiotic back out of the cell
  through their plasma membrane.
• Bacteria can destroy the antibiotic once inside
  the cell.
• Bacteria can bind other substances to the
  antibiotic once inside the cell in order to
  inactivate its action.

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How is Antibiotic Resistance Acquired?

• MOST BACTERIA DO NOT NATURALLY POSSESS
  RESISTANCE TO ANTIBIOTICS!!
• (Other than their own that they produce for
  example - Streptomycetes are resistant to
  Streptomycin)

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Antibiotic Resistance is Acquired Through

• Natural mutation
• Exchange of genes through
• Conjugation
• Transduction
• Transformation

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Conjugation

• Bacteria connect to each other using a
  thread-like structure called a pilus. A section
  of DNA often a circular piece of DNA called a
  plasmid is transferred from one bacterium to the
  other.

Illustrations from Doc Kaisers Microbiology Home
Page http//student.ccbc.cc.md.us/courses/bio141/l
ecguide/unit4/genetics/recombination/
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Transduction

• A virus can take up a piece of DNA from its
  bacterial host and insert it into its own viral
  genome. It then takes over the bacterial cell
  host and replicates many copies of the virus.
  The bacterial cell is ruptured and the replicated
  viruses erupt from the infected cell. When one of
  the viruses infects a new cell, it inserts the
  original bacterial DNA into the new cell, where
  the stolen piece becomes integrated into the new
  cell's DNA.

Illustrations from Doc Kaisers Microbiology Home
Page http//student.ccbc.cc.md.us/courses/bio141/l
ecguide/unit4/genetics/recombination/
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Transformation
DNA from dead bacteria is taken in and
incorporated into the genome of living bacteria
Illustrations from Doc Kaisers Microbiology Home
Page http//student.ccbc.cc.md.us/courses/bio141/l
ecguide/unit4/genetics/recombination/
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So Whats the Big Deal if One or Two Bacteria
Have Antibiotic Resistance?

• If the antibiotic resistance offers a competitive
  advantage to the bacteria, other bacteria will
  die off, and the resistant bacteria will thrive.
• Within that particular environment, rapid
  resistant bacterial reproduction would lead to
  the development of a resistant strain that could
  cause harm to humans and other living things.