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20 Cards in this Set
- Front
- Back
Extended Spectrum Beta-Lactamases (ESBL's) are found in what organisms?
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exclusively in Gram negative organisms, primarily in Klebsiella pneumoniae, Klebsiella oxytoca, and Escherichia coli but also in Salmonella, Proteus, Enterobacter, Citrobacter, Serratia, and Pseudomonas spp.
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Spectrum of Extended Spectrum Beta-Lactamas (ESBL) antibiotic resistance
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Typically confer resistance to penicillins, first-generation and some third-generation cephalosporins (eg, cefotaxime, ceftazidime, and ceftriaxone).
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First generation cephalosporin
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Cefazolin
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Antibiotic class of cefuroxime, cefoxitin, and cefotetan
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2nd generation cephalosporins. Cefoxitin and cefotetan belong to the Cephamycin subgroup.
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Antibiotic class of cefotaxime, ceftriaxone, ceftizoxime, cefoperazone and ceftazidime
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Third generation cephalosporins
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Third generation cephalosporins
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cefotaxime, ceftriaxone, ceftizoxime (poor acticity against Pseudomonas aeruginosa); cefoperazone and ceftazidime (good acticity against Pseudomonas aeruginosa)
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Antibiotic class of Cefepime
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Fourth generation cephalosporin
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Antibiotic class - Cefazolin
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First generation cephalosporin
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Beta-lactam antibiotics: bactericidal or bacteriostatic?
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bactericidal
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Distinguishing feature between plasmid-mediated and chromosomal AmpC beta lactamases.
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chromosomal: inducible; plasmid-mediated: not inducible
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Which Enterococcus species is most commonly associated with Vancomycin resistance?
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E. faecium
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Two species of Enterococcus with intrinsic Vancomycin resistance. What genotype is responsible?
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Enterococcus gallinarum and E. casseliflavus. Low-level Vanc resistance (MIC’s < 32 mcg/ml) is conferred by the chromosomal, non-transferrable vanC genotype (a cluster of genes). The vanC genotype results in peptidoglycans with a terminal D-alanyl-D-serine (wild type is D-alanyl-D-alanine) with reduced vancomycin affinity.
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Vancomycin-resistant S. aureus is now being treated with what drug
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Quinupristin-dalfopristin
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What does MRSA look like on chromagar
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MRSA colonies are pink. Methicillin-sensitive S. aureus will not grow, and other bacteria are blue.
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Antobiotic for elimination of nasal carriage of Staph aureus
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Mupirocin, topically
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Nitrocefin is a colorimetric reagent used for detecting
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beta lactamase
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Glycopeptide inetrmediate staph aureus refers to:
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SA with intermediate resistance to glycopeptide antibiotics, i.e. vancomycin. The bug is sensitive to vanc at doses of 8-16mcg/ml
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E-test for ESBL detection
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The E test ESBL strip carries two gradients, on the one end, ceftazidime and on the opposite end ceftazidime plus clavulanic acid. MIC is interpreted as the point of intersection of the inhibition ellipse with the E test strip edge. Ratio of ceftazidime MIC and ceftazidime clavulanic acid MIC equal to or greater than 8 indicates the presence of ESBL.
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Spectrum of activity of TEM-1 and TEM-2 beta-lactamases
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Confer resistance to penicillins and narrow spectrum cephalosporins (eg cephalothin or cefazolin)
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Name two mechanisms for resistance to carbapentems (imipenem, meropenem). How do you tell which it is by a micro test?
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Porin mutation (no entry) and/or efflux, metallo beta-lactamse (antibiotic breakdown). Larger zone of inhibition to imipenem than meropenem suggestive of entry inhibition (mira can enter via a different route, impenem requires a specific porin that can be mutated). E-test with imipenem +/- EDTA will demonstrate presence of metallo (zinc-containing) beta-lactamase. (EDTA should make the drug more active on the plate).
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