BIOL243 L12 Antimicrobial Resistance

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  • Created by: Katherine
  • Created on: 27-04-17 22:31
What is antimicrobial resistance?
The abilit of an organims to resist the action of an antimicrobial rug.
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When did Staphylococcus become resistant to penicillin?
In 1959 - - Penicillin was introduced in 1940.
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When did MRSA start to arise?
The first case of MRSA occurred just after 1960.
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Give some reasons for increasing antimicrobial resistance?
Inappropriate use of antibiotics, Weak or absent antimicrobial resistance surveillance and monitoring systems. Poor infection prevention. Insufficient diagnstic, inadequate systems to ensure quality.
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Doctors may wrong perscribe antibiotics, but how else may antibiotics be inappropriately used?
In animal husbandry, and also in agriculture. If you eat the animal which has bacteria which are resistance, you too may gain resistance.
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How do we conduct antimicrobial resistance surveillance? And why don't we always?
We put patients with resistance bacteria in separate areas, and we wear protective gear to prevent spread - we may not have the facilities.
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Why is antimicrobial resistance a problem?
Leads to treatment failure, increased mortality, increased health care cost, resistance spread in the community, spread of resistance from acute to primary care and from country to country
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How does resistance happen?
Intrinsic resistance and acquired resistance
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What is intrinsic resistance
Naturally occuring: resistance occuring due to normal genetic, structural or physiological state of the organims
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How does acquired resistance occur?
Resistance that results from altered genetic, structural or physiological state of the organism. Induced genetic mutation (after pressure from antibiotics) of aquired by transfer of genetic material from one bacteria to another.
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What are different ways in which microorganism can be resistant to antibiotics? 1
Lack or target bindng site or altered binding site: bacteria without cell wall are resistant to penicillin. Efflux pump: some bacteria posses pump that exports the antibiotic outside the cell, production of an enmye that inactivates antibotics
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Give an example of the production of an enzyme that inactivates antibiotics?
Beta lactamases, cephalosporinases, carbepoamases.
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Give an example of a bacteria which posses pumps that export the antibiotic outside the cell
Psedomonas
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What are different ways in which microorganism can be resistant to antibiotics? 2
Alternative metabolic pathways, decreased permeability or loss or porin channels. Formation of biofilm
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What happens when alternative metabolic pathways are used?
This is when an antibiotic acts by inhibiting a metabolix pathway in the microorganism by the cell revets to using an alternative apthway to evade the action of the antibiotic.
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What does decreased permeability do to the anitibiotic?
It prevents antibiotic entry
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Why does formation of the biofilm effect the antibiotic?
In a biofilm, the bacteria adhere to a surface, stick to each other and are covered with a polymeric substance (slime0. Tthis prevents penetration of the antibiotics. The bacteria in a biofilm doe not actively replicate, recuding antibiotic activity
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What is the resistance mechanism of beta lactams? E.g. penicillin and cephalosporins?
Enzymatic destruction of the beta lactam ring by beta lactamase.
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What is the resistance mechanism of aminoglycosides?
Modifying enzyme alter the aminoglycosides molecule and make it difficult to bind to ribosomes. Reduces uptake due to ribosomes. Reduces uptake to decreased porin channels. Altered ribosomal binding site.
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What is the resistance mechanism of tetracyclines?
Reduces uptake and effluc pump
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What is the resistance mechanism of Quinolones?
Decreased uptake and altered DNA gyrase binding site.
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What is acquired genetic transfer?
Genes that confer resistance can be carrier on chromosomes or plasmids.
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What are plasmids?
Extra-chromosomal genetic material that moves easily from one bacteria to the other. Plasmids move from one bacteria to another by: transduction, conjugation or transformation.
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What is the method of transduction?
A phage infects the donor bacteril cell. Page DNA and proteins are made, and bacterial chromosome is broken down into pieces. Bacterial DNA is packaged in a phage capsid. Then the donor cell lyses and releases phage particles containing bacterial DNA
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What are the next steps of transduction?
A phage carring bacterial DNA infects a new host cell, the recipient cell. Recombination can occur producing a recombinant cell with a geneotype different from both the donor and recepient cells.
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What are the stps of conjugation?
The sex pilus contacts the recipinet F- cell. The plasmif is activated for transfer when an endonuclease cleaves one strand of DNA at the origin of transer. The sex pilus retracts and pulls the donor and recipient apart. The F plasmid is transferredd
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What is the final step of conjugation?
The complementary strands to both F plasmid strands are synthesissed int the donor and recipient cells. Both cells are F+ and synthesize the sex pilus.
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What is transformation?
Recipient cell takes up donor DNA. Recombination occurs between donor DNA and recipient DNA.
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What are extended spectrum beta lactamases?
A group of enzymes produced by gram negatics responsible for extensive resistance to beta lactam antibiotics. The gene for this resistance is carried on a plasmid and transferable from on bacteria to the other. Previously seen in hospital isolates.
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Where are ESBLs found?
Previously seen in hospital isolates but now found in lots of community isolates. Causes hospital outbreaks and can only be treated with a limited antibiotics.
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How is labatory detection of resistance done?
Disc diffusion testing: has a standard zone measurement for interpretation
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What is the disc diffusion test?
We use different discs of antibiotics to test against a bacteria
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What is an E test?
A method which uses antibiotic *****s. You can check the minimum inhibitory concentration as the ***** varies in concentration.
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What is automated sensitivity testing? How is it done?
In a vitek machine - Dilute the bacteria in some normal saline/water and put into a machiene and it tells you what the bacteria is sensitive to automatically.
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How is resistance in bacteria determinied molecularly?
Using PCR -
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What are the solutions put into place to fix the problem of resistance?
Synergistic action of multiple antimicrobials. Look after the antimicrobial agents that we have. Find alternative antimicrobial agents and technologies.
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What are ways in which we can look after the antimicrobial agents that we currently have?
Antimicrobial stewardship globally and better diagnostics and surveillance
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What are the methods of finding alternative antimicrobial agents and technologies?
New antimicrobial drug classes and vaccine devleopment and immunotherapy.
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What is the UK strategy for controlling antimicrobial resistance?
Optimising prescribing practice. Improving evidence through surveillance and research. Improving infection prevention and control. Raising awareness/changing behaviour. Develop new drugs. Strengthening UK and international collaboration
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Card 2

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When did Staphylococcus become resistant to penicillin?

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In 1959 - - Penicillin was introduced in 1940.

Card 3

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When did MRSA start to arise?

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Card 4

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Give some reasons for increasing antimicrobial resistance?

Back

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Card 5

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Doctors may wrong perscribe antibiotics, but how else may antibiotics be inappropriately used?

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