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1. Cell Membrane

2. How bacteria resist antibiotics

3. Genetic exchanges that confer antimicrobial resistance

4. FDA video: antimicrobial resistance


 

HOW RESISTANCE IS CONFERRED

HOW DO ANTIBIOTICS KILL BACTERIA?
Antibiotics work in many ways. Several ways in Which antibiotics kill bacteria are listed below and shown in Figure 1:

1. Interfere with bacterial cell wall synthesis
2.
Disrupt bacterial protein synthesis at the ribosome
3. Inhibit function of enzymes involved in DNA synthesis by masquerading as a natural component of the synthetic machinery

MECHANISM OF RESISTANCE DEVELOPMENT
Bacteria can develop resistance through genetic mutation (“resistance genes”). These mutations enable the bacteria to alter the way it interacts with the antibiotic agent, rendering the antibiotic harmless. Such mutations cause the following to happen (Figure 2):

  • Efflux (of the antibiotic)—bacteria develop methods to throw antibiotics out of the cell (efflux) or decrease their uptake (influx).
  • Membrane plug formation—a protein is produced to block the uptake of drug into the cell.
  • Ribosomal blockade—the bacteria produces a protein that blocks the ability of the antibiotic to bind to ribosomes.
  • Enzymatic destruction—the bacteria produces an enzyme that destroys the antibiotic before it can produce its effect.
  • Alteration of the drug—the antibiotic itself is altered by bacterial enzymes, making it ineffective.

BACTERIA TRANSFER RESISTANT GENES TO ONE ANOTHER
Bacteria can share the DNA that makes them resistant to antibiotics with other bacteria in their environment. Bacteria share DNA with other bacteria through these mechanisms (see Figure 3):

  • Transformation—the uptake of free DNA in the environment. The free DNA usually comes from the breakdown of dead bacteria nearby.
  • Conjugation—the transfer of plasmids, or small circular pieces of bacterial DNA, containing resistance genes, from one bacteria to another.
  • Transduction—the transfer of bacterial DNA via viruses, or bacteriophages, to other closely-related bacteria. Bacteriophages are viruses that infect only bacteria.

SHORT VIDEO ON ANTIMICROBIAL RESISTANCE
Click the icon in Figure 4 to be redirected to the video page.



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