Term
| What are some mechanisms of bacterial resistance? |
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Definition
1. Target changes
2. Decrease permeability
3. bind -up antibiotic
4. Efflux pumps
5. Bypass inhibited process
6. overproduction of target
7. Enzymatic inactivation |
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Term
| Bacteriodes fragilis is resistant to gentamicin having acquired a plasmid carrying a gene producing aminoglycoside-hydrolyzing enzymes. T or F? |
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Definition
| False. It's bc amino glycosides can't get into the cytoplasm of anaerobic bac bc there's no ETC |
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Term
| What is the difference between intrinsic and acquired resistance? |
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Definition
Intrinsic - something that's there already... ex) aminoglycoside resistance due to lack of ETC
Aquired - from outside sources |
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Term
| Where are the Penecillin Binding Proteins? |
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Definition
| Inside the cell wall on the inner membrane |
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Term
| What is the target of gentamicin? |
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Definition
targets the ribosomes!
Cidal! bc it causes membrane protein problems! -> leakage |
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Term
| How does gentamicin reach its target in GNR's (Gram negative rods)? |
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Definition
1. Through outer membrane via porins (originally there to regulate osmolarity)... drawn into the (-) charge in the periplasmic space
2. Uses the ETC to cross the cytoplasmic space
2. |
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Term
50 yo female w. prolonged hospitalization due to complications from cholecystectomy. Has ventilator associated pnum due to PSUEDOMONAS AERUGINOS and is started on CEFTAZIDIME.
7 d later, recurrent fever prompts blood cultures which grow PSEUDOMONAS AERUGINOSA now resistant to CEFTAZIDIME.
DNA fingerprinting shows they're the same bug.
Intrinsic or aquired? |
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Definition
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Term
| How does Ceftazidime reach it's target? |
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Definition
Target : PCN binding Protein (PBP)
Goes through porins to get to the inner membrane |
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Term
| How can different organisms become resistant to Ceftazidime? |
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Definition
1. create beta-lactamase
2. efflux pump
3. ...etc |
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Term
| How can resistance genes be passes? |
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Definition
1. conjugation
2. Transduction (via bacteriophage)
3. Transformation (naked free DNA) |
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Term
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Definition
| proportional to how much of that antibiotic is around the area... |
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Term
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Definition
| proportional to how much of that antibiotic is around the area... |
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Term
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Definition
| bind to D-ala Terminus and prevent cell wall formation |
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Term
| How does S. aureus develop resistance to penecillin? |
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Definition
| Penicillinase (beta-lactamase) |
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Term
| How do PCNase resistant PCN's work? |
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Definition
modify the PCN with aromatic ring to block where the PCNase is binding. (PCNase resistant PCN)
2. |
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Term
| What change will make bugs resistant to all beta-lactams? |
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Definition
Change in the PDP2 (normal) -> PBP2A
***Carried on MecA mobile operon in plasmid |
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Term
| How can methicillin resistance be overcome? |
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Definition
Use non PDP targets!
ex) Ribosomes: Macrolides, Aminoglycosides, tetracyclines, Vancomycin, Daptomycin |
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Term
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Definition
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Term
| What is the mainstay Tx for MRSA? |
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Definition
Vancomycin
*big!! hydrophilic |
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Term
| Why are G(-) rods resistant to Vancomycin? |
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Definition
| Vancomycin is too big to get in through the porins on the outer membrane. |
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Term
| How can MRSA develop vancomycin resistance? |
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Definition
1. Modify the D-ala terminus -> D-ala D-Lac
** carried on vanA gene
2. Making more peptidoglycan! Increases targets to soak up drugs till the assault it over. low grade resistance but much more common! |
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Term
| What does the plasmid-mediated vanA gene carry? |
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Definition
| Vancomycin resistance by changing D-ala D-ala -> D-ala D-lac |
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Term
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Definition
| <2 microgram/mL ...<1 is better |
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