weird conditions of antibioitcs
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- 3 reasons why bacterium should be suscept but patient doesnt respond
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-acidic pH at infection site decreases med action.
-vascular occlusion prevents med from reaching site.
-immunological factors require bacteriocidal and you gave a STATIC DUMMY - 3 REASONS WHY A PATIENT SHOULDNT RESPOND BUT DID!!
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1. acid pH site increases some activity
2. kidney concentrates antibiot, high enough levl kills bug
3. host defense mechanisms just work - 6 events that precipitate resistance
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1. natural selection
2. overuse of antibiots
3. overuse of broadspectrum
4. poor patient compliance
5. international travel, rapid spread of resistance.
6. feeding antimicrobials to livestock - 2 categories of developing resistance
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a. chromosomal mutation of indiv cell
b. resistance gene trasnfer between cells - 2 ways to develop chromosomal mutation of individ cell
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-somatic mutation (spontaneous)
-selective pressure (exposing to antibiots pressures them to mutate) - 4 ways to transfer R genes
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-transduction
-conjugation
-transformation
-plasmid transfer - who does conjugation occur in?
- only gram negative bugs
- how is resistance transferred in transduction?
- via a BACTERIOPHAGE in gram positives or negatives. a bacteriophage is a virus that only infects bacteria
- transformation; what is it?
- transfer of bacteria-free genetic material into bacteria; causes resistance
- plasmid transfer
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-non-chromosomal dna
R-plasmids
transferred by any of the other three methods of transfer, also
TRANSPOSONS - jumping from one plasmid to another - this is translocation. - 4 mechanisms of resistance
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-altered antimicrobial target site
-inactivate antibiotic by producing an enzyme
-change cell membrane permeability
-combine mechanisms - 2 ways to alter permeability
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decrease uptake - porins
efflux - pump antibact out! - 2 ways to modify antimicrobial's target to resist it:
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-change penicillin binding proteins (PBP) - penicillin can't bind and inhibit bug.
-alter enzyme or ribosome target - new replacement is not susceptible. - principal of therapeutic drug monitoring
- when amount of drug necess for treatment is considerably high, have to monitor activity so that toxic levels aren't reached.
- multidrug resistance
- resistance of a bacteria to multiple drugs
- how multidrug resistance is caused
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plasmids can have more than one resistance gene, transfers all to bacteria. MDR GNB
multiple r-genes can accumulate on the chromosome. MDR TB - MDR TB - caused by?
- multi drug resistance - accumulation of r-genes on the chromosomes
- mdr gnb - caused by?
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multidrug resistant gnb
transfer of conjugal plasmid with multiple resistance genes - esbl
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extended spectrum betalactamase
-ß-lactamases capable of hydrolysing extended spectrum cephalosporins and penicillins and aztreonam.
-associated with E. coli or Klebsiella pneumoniae