Term
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Definition
-They are large, **self-transmissible plasmids
-Common in gram-
-(really it's old terminology for antibiotic Resistance transmitting plasmids) |
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Term
| How is resistance to b-lactams generated? What is the difference from gram- to gram+ |
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Definition
-Due to *b-lactamases (penicillinase, cephalosporinase)
-Cleaves at bottom of square next to =O bond
-Gram+ expression has to be induced by b-lactams, and the b-lactamase is excreted extracellularly
-In Gram-, expression is constitutive and the enzyme is in the periplasmic space
-The other way is to simply alter the penicillin binding protein (transpeptidase) |
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Term
| What are two mechanisms for resistance to aminoglycosides? |
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Definition
-These are streptomycin and kanamycin (bind 30S)
-Can either alter transport, or inactivate enzyme by;
1. Acetylation of amino
2. Phosphorylation of OH
3. Adenylation of OH |
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Term
| How is resistance to tetracycline generated? |
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Definition
-also binds 30S
-Can actively excrete the drug, or decrease permeability
-Very common in enterobacteriaceae |
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Term
| How is chloramphenicol resistance generated? |
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Definition
-Binds 50S and inhibits peptide bond
Inactivated by enzyme;
-**chloramphenicol acetyltransferase
-Also, anerobes can reduce a *p-nitro group |
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Term
| Give the 5 drugs that have their targets altered in order to gain resistance? What is altered? |
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Definition
1. Macrolides (erythromycin); 23S is methylated (on 50S)
2. Rifampin; beta unit of DdRp is altered
3. B-lactams; penicillin binding protein is altered
4. Vancomycin; pep. precursor is altered
5. Streptomycin; 12S of 30S is altered |
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Term
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Definition
-Methicillin-resistant Staphylococcus aureus
-Resistant to penicillins and cephalosporins (**B-lactams)
-Treat it with **vancomycin |
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Term
| What specifically is changed in vancomycin resistance? What is the plasmid called? |
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Definition
-Usually binds to the D-ala-D-ala
-But it gets changed to **D-ala-D-alanyl lactate
-Due to **VanA plasmid |
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Term
| How is trimethoprim resistance acquired? Sulfonamide resistance? |
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Definition
-Both from R plasmids that encode resistant enzymes (altered binding site)
-For trimethoprim it's dihydrofolate reductase
-For sulfonamide it's dihydropteroate synthetase |
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