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17 Cards in this Set
- Front
- Back
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Constitutive vs Inducible?
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B-lactamases can be constituitively (constantly) expressed, or Induced expression (eg by antibiotics)
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What are the B-lactamase classifications?
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Ambler (based on differences in amino acid sequences)
Bush-Jacoby (based on different substrates/B-lactams) |
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Which B-lactamase classes are plasmid mediated?
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Bush-Jacoby Class 1 (and most of class 2 and 3)
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What is the most problematic B-lactamase class?
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Bush-Jacoby Class 2be
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Whats a "stably derepressed mutant"?
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Bacteria that have a mutation that inhibits the inhibtion of their own B-lactamase production.
They now produce B-lactamase constituitively when induced by an antibiotic. |
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Give example(s) of bacteria that tend to have more stably derepressed mutants.
Give example(s) of B-Lactams that tend to induce derepressed mutants. Whats the classic example of a drug that induces a stably derepressed mutant? |
SPICE organisms
Known inducers of Bush class 1 chromosomal B-Lactamases: Cefoxitin, Imipenem, (3rd gen cephs: cefotaxime,ceftriaxone,ceftazidime) Classic ex: Ceftazidime inducing an Enterobacter mutant Note: The stably derepressed mutation is associated with bush class 1 chromosome B-Lactamase genes, not with other classes like class 2be plasmid B-Lactamase genes (seen in ESBLs). |
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List all the SPICE organisms
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Serratia
P. aeruginosa Indole + Proteus Citrobacter Enterobacter "SPICE" |
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If class 1 chromosomal B-lactamases are suspected, which antibiotics should NOT be given to the px?
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3rd gen cephalosporins(me: cefotaxime,ceftriaxone,ceftazidime)
Piperacillin/Tazobactam(Tazo cant inhibit these B-Lactamases) Note: Cefoxitin and Imipenem werent mentioned, but IBLV you would also not give these. |
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If class 1 chromosomal B-lactamases are suspected, which antibiotics SHOULD be given to the px?
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Cefepime (4th gen)
Carbapenems These are just more stable to the class 1 chromosomal B-lactamases than other antibiotics. Q: Since SPICE organisms are associated with class 1 chromosomal B-Lactamases, are carbapenems and cefepime the goto drugs for SPICE organisms? |
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What are ESBLs, and which bugs have them?
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Extended Spectrum B-lactamases
Produced by K. pneumonia and E. coli Bush class 2be (from mutant 2b genes) IBLV theyre more problematic because they hydrolize a wider spectrum of B-Lactams, and because the genes are on a plasmid they're more transferable. |
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When ESBL producing organisms are suspected, which antibiotics should be avoided?
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3rd gen cephalosporins
Aztreonam (monobactam) Note: This is just like when we asked about which antibiotics should be avoided when bush class 1 chromosomal B-Lactamases are suspected, here we're concerned with bush class 2b and 2be plasmid B-Lactamases. Note: The bush classifications are just a way of grouping B-Lactamase genes, but we associate microorganisms with these classes because they contain some of these genes. |
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When ESBL producing organisms are suspected, which antibiotics should be used?
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Carbapenems(drug of choice)
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The higher Bush class 2's and the Bush class 3's are ______
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Genes that code for Carbapenemases (enzymes that break down carbapenems).
So you cant use carbapenems against the high class 2b or any of the class 3 bacteria. But you want to use them for class 1, and class 2b/2be. |
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Whats the most dominant B-lactamase gene in the world?
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CTX-M
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How do bacteria dec their permeability to pcns?
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They downregulate their expression of porins so pcns have fewer "doors" to enter(for gram - only).
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What are these: MexAB-OprM, MexCD-OprJ, MexEF-OprN, MexXY-OprM?
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Genes for (over expressed) efflux pumps produced by just one bacteria (P. aeruginosa)
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What kind of resistance do efflux pumps confer?
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Besides over-expression leading to very active efflux of drugs, each pump can pump out a broad spectrum of drugs confering multi-drug resistance to that bacterium
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