Antibiotic resistance

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  • Created by: hadar
  • Created on: 03-02-18 16:30
What are the 2 types of general resistance mechanisms?
1) innate- bacteria has this property- relates to permeability/entry of antibiotic 2) acquired- get a genes which poses a defensive mechanism
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How can bacteria acquire a resistance gene?
1) horizontal transfer 2) spontaneous mutation (new mutation)
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What antibiotics are gram -ve resistant to?
glycopeptides, daptomycin
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What antibiotics are gram +ve resistant to?
aztreonam, colistin
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What antibiotics are gram anaerobes resistant to?
aminoglycosides
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What antibiotics are gram streoptococci resistant to?
aminoglycosides
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What are the 5 types of resistance mechanism?
1) drug efflux 2) absent target 3) decreased permeability 4) target modification 5) enzymatic degradation
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Describe absent target resistance mechanisms
Introduce antibiotic to a micro-organism aimed at a particular target that isn't there Cant target it if it isn't there
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Describe decreased permeability resistance mechanisms
don’t take up the antibiotic - Vancomycin:Gram-negative bacilli Gram-negatives have an outer membrane that is impermeable to vancomycin Gentamicin:anaerobic organisms Uptake of aminoglycosides requires an O2 dependent active transport mechanism
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Describe target modification resistance mechanisms
the antibiotic cannot engage with the target since it has been changed Altered penicillin binding protein – the protein isn't recognized by the antibiotic and it cannot bind to it anymore
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Give examples of target modifications resistance
Flucloxacillin:MRSA Altered penicillin-binding protein (PBP2’, MecA gene) doesn't bind β-lactams Vancomycin:VRE Altered peptide sequence in Gram-positive peptideoglycan (D-alaD-ala→D-alaD-lac)Reduces binding Trimethoprim gram-ve bacilli dhr mutation
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Describe enzymatic degradation resistance mechanisms
the antibiotic is broken-down so it cannot function and wont have effect- e.g. b-lactamases- degrade b-lactams  can give a b-lactamase inhibitor
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Give examples of enzymatic degradation resistance
Penicillins+cephalosporins: β-lactamases Staphylococcal penicillinase-ESBL- Inactivate penicillins and cephalosporins Carbapenemases Gentamicin: aminoglycoside modifying enzymes Chloramphenicol:chloramphenicol acetyltransferase (CAT)
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Describe drug efflux resistance mechanisms
active efflux mechanism  pumped out of the cell Common in fungi for azoles+ in gram –ve bacteria
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How is resistance spread in genes?
single genes encode resistance mechanism- encoded in plasmids
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What does horizontal transfer allow for in resistance?
Enabled by transposons and integrons DNA sequences designed to be transferred from plasmid to plasmid and/or from plasmid to chromosome Often contain ‘cassettes’ with multiple resistance genes
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What does vertical transfer allow for in resistance?
Chromosomal or plasmid-borne resistance genes transferred to daughter cells on bacterial cell-division
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Define antibiotic era
Term used to describe the time since the widespread availability of antibiotics to treat infection
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Describe post-antibiotic era
Term used to describe the time after widespread antibiotic resistance has reduced the availability of antibiotics to treat infection
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List bacteria with resistance
1)Meticillin-resistant Staphylococcus aureus (MRSA) 2)Vancomycin/glycopeptide-resistant enterococci (VRE/GRE) 3)Extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL) 4)Carbapenemase-producing Enterobacteriaceae (CPE)
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What are enterocacteriaceae resistant to?
amoxicillin, ciprofloxacin, gentamicin, carbapenems etc.
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What are pseudomonas resistant to?
ceftazidime, carbapenems etc.
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What is TB resistant to?
1)Multi-drug resistant tuburculosis (MDR-TB) 2)Extremely-drug resistant tuberculosis (XDR-TB)
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What is empirical therapy?
based on experience and, more specifically, therapy begun on the basis of a clinical educated guess in the absence of complete or perfect information
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What are the implications for empiric therapy?
1) Risk of under-treatment if ‘traditional’ antibiotic is used 2)Risk of excessively broad-spectrum treatment if risk of resistance is taken into account
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What are the implications for targeted therapy?
1) expensive 2) toxic 3) last line drugs used
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What is the most effective antibiotic for staph aureus?
Flucloxicillin
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What does sensitivity testing determine?
whether minimum inhibitory concentration (MIC) is above a predetermined ‘breakpoint’ level
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How is sensitivity testing used?
1) inform antibiotic therapy 2) provide epidemiological data
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How does sensitivity testing inform antibiotic therapy?
1)First-line antibiotic choice if infection does not require immediate treatment 2)Second-line choice after empiric therapy 3)Second line choice after failure of initial therapy
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How does sensitivity testing provide epidemiological data?
Sensitivity results are collated locally, nationally and internationally To inform local guidelines and antibiotic choices To provide epidemiological data To provide early warning of threats to public health
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Other cards in this set

Card 2

Front

How can bacteria acquire a resistance gene?

Back

1) horizontal transfer 2) spontaneous mutation (new mutation)

Card 3

Front

What antibiotics are gram -ve resistant to?

Back

Preview of the front of card 3

Card 4

Front

What antibiotics are gram +ve resistant to?

Back

Preview of the front of card 4

Card 5

Front

What antibiotics are gram anaerobes resistant to?

Back

Preview of the front of card 5
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