Antibiotics and Resistance

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Antibioticsand Resistance

• Prepared by Stephanie Aldret
• Cell Physiology
• Fall 2002

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What is an Antibiotic?

• An Antibiotic is a chemical substance that
  inhibits bacterial growth or kills bacteria it
  is produced naturally by bacteria and fungi.

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How does an Antibiotic Work?

• An Antibiotic
• Prevents the cell wall from forming
• Prevents protein synthesis
• Interferes with nucleic acid synthesis
• Disrupts plasma and/or outer membranes
• Serves as an antimetabolite

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Types of Antibiotics

• Beta-lactam antibiotics keep the cell wall from
  forming.
• Tetracyclines, Aminoglycosides, and Macrolides
  interfere with translation or inhibit polypeptide
  growth.
• Quinolones bind to bacterial RNA polymerase and
  inhibit RNA synthesis.
• Polymixins act as detergents and bind to
  phospholipids in the plasma membrane Polyenes
  bind to sterols in fungi.
• Sulfa drugs interfere with bacterial metabolism.

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What is Antibiotic Resistance?

• Antibiotic Resistance is the ability to resist
  the harmful effects of antibiotics by
• Alteration of target receptor proteins
• Prevention of entry into the cell
• Destruction of antibiotic upon entry
• Association with antibiotic which blocks entry
• Pump antibiotic out of cell before activation
• Bypass affected step in the metabolic pathway
• It is rare for a bacterium to possess more than
  1, but it is known that the Mycobacterium
  tuberculosis is resistant to all present
  antibiotics.

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How does a bacterium become Antibiotic Resistant?

• Genetic Mutation
• Genetic material taken in by a cell and
  incorporated into chromosomal DNA or a plasmid.
• Plasmid resistant bacterium are referred to as
  strains and only progeny of the resistant cells
  will remain resistant.
• Antibiotic Resistance is most easily acquired
  within a limited environment with routine,
  consistent antibiotic exposure (ie. Hospitals,
  individuals on long-term antibiotic therapy, farm
  animals treated with low, non-therapeutic doses
  of antibiotics for weight gain).

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Side Effects of Antibiotics

• Toxicity
• Allergy
• Disruption of Normal Microflora

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Limiting Antibiotic Resistance

• Use high doses of antibiotics long enough to kill
  or weaken bacteria enough for natural defenses to
  kill them
• Synergism/Potentiating drug interactions
• Restrict to essential use only

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Summary

• Antibiotics are chemical substances produced by
  bacteria and fungi that are used to kill bacteria
  by interfering with cellular processes.
• Antibiotic Resistance is the ability to resist
  the harmful effects of antibiotics.
• Resistance is acquired through genetic mutation,
  the ingestion of genetic material for resistance,
  or continuous exposure to low doses of
  antibiotics.
• Resistance can be prevented by taking all of your
  prescribed antibiotics, taking multiple
  antibiotics at one time, and restricting
  antibiotic use to individuals with weakened
  immune systems.

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Questions

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