bacterial drug resistance n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Bacterial Drug Resistance PowerPoint Presentation
Download Presentation
Bacterial Drug Resistance

Loading in 2 Seconds...

play fullscreen
1 / 16

Bacterial Drug Resistance - PowerPoint PPT Presentation


  • 200 Views
  • Uploaded on

Discovery of penicillin 1929. Sir Alexander Fleming. Accidental mold contamination. Chinese, Egyptians, Europeans used moldy food to treat infections. Bacterial Drug Resistance. Bacterial Resistance. Many bacterial have developed antibiotic resistance.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Bacterial Drug Resistance' - deanna-sandoval


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
bacterial drug resistance
Discovery of penicillin 1929.

Sir Alexander Fleming.

Accidental mold contamination.

Chinese, Egyptians, Europeans used moldy food to treat infections.

Bacterial Drug Resistance
bacterial resistance
Bacterial Resistance
  • Many bacterial have developed antibiotic resistance.
    • 80% of Staphylococcus resistant to penicillin.
    • “Superbugs” resistant to all antibiotics.
    • Multi-drug resistant tuberculosis.
  • Misuse of antibiotics accelerates rates of resistance.
antibiotic examples
Antibiotic Examples
  • b-Lactam antibiotics (e.g., Penicillin):
    • Transpeptidase crosslinks the peptidoglycan net in the cell wall of Gram-positive bacteria.
    • The b-lactam ring mimics a component of the cell wall to which transpeptidase binds, inhibiting the binding of transpeptidase.
    • Bacterium lyse (rupture) because the cell wall is weakened.
  • Disrupters of nucleic acid synthesis prevent bacterial cell division.
    • The antibiotic rifampin interferes with prokaryotic RNA polymerase.
    • Fluoroquinolones inhibit DNA gyrase.
  • Disrupters of protein synthesis:
    • Aminoglycosides inhibit nucleic acid or protein synthesis in bacteria.
    • L-shaped molecules that fit into pockets of bacterial ribosomal RNA.
    • When they insert themselves into rRNA, they disrupt ribosomal structure.
    • L-shaped pocket is specific to bacteria.
mechanisms of resistance
Mechanisms of Resistance
  • Bacteria either have preexisting resistance to drugs, or they develop resistance.
  • Often resistance to a certain drug from a particular class leads to resistance to all other drugs in that class.
inherent resistance
Inherent Resistance
  • Darwinian evolution:
    • Bacteria that resist an antibiotic's effects are better suited to survive in an environment that contains the antibiotic.
    • Genes that confer resistance are transferred to the bacterial progeny.
  • Bacteria naturally resistant (e.g., Gram-negative bacteria resistant to penicillins).
  • Bacteria may be resistant because
    • They have no mechanism to transport the drug into the cell.
    • they do not contain or rely on the antibiotic’s target process or protein.
acquired resistance
Acquired Resistance
  • Bacteria that don’t begin life resistant to a certain antibiotic can acquire that resistance.
  • Horizontal evolution:
    • Resistance genes pass from a resistant strain to a nonresistant strain, conferring resistance on the latter.
    • Presence of a antibiotic is a selective pressure.
  • Gene transfer mechanisms:
    • Conjugation.
    • Transduction.
    • Transformation.
conjugation
Conjugation
  • Transmission of resistance genes via plasmid exchange.
  • Resistance spreads much faster than simple mutation and vertical evolution would permit.
transduction and transformation
Transduction and Transformation
  • Transduction: Virus transfers gene.
  • Transformation: DNA released from a bacterium is picked up by a new cell.
mechanisms of resistance1
Mechanisms of Resistance
  • Enzyme-based resistance–break down or modify antibiotic.
  • Ribosomal modifications–methylation of ribosome interferes with antibiotic binding.
  • Protein modifications–mutations leave target protein unrecognizable to antibiotic yet still functional.
  • Metabolic resistance–overcome competitive inhibition by producing excess of metabolite.
  • Effluxing the toxin–pump it out.
enzyme based resistance b lactamase
Enzyme-Based Resistance: b-Lactamase
  • Enzymes can destroy or disable antibiotics.
  • For example, b-lactamase hydrolyzes b-lactam ring of penicillins.
  • Without a b-lactam ring, penicillins ineffective.
enzyme based resistance aminoglycoside disruption
Enzyme-Based Resistance:Aminoglycoside Disruption
  • A bacterial enzyme adds a bulky substituent to the aminoglycoside (such as chloramphenicol).
  • Antibiotic now does not fit into the rRNA pocket, rendering it harmless.
conclusion
Conclusion
  • We overuse antibiotics and often neglect to complete a full course of antibiotics once it has been prescribed, leading to the spread of antibiotic resistance.
  • Resistance can disappear if there is no selective pressure to maintain resistance.