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27 Cards in this Set
- Front
- Back
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.antibiotic
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a drugthat kills or inhibits growth of microorganism.
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resistant.
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antimicrobial will not inhibit bacterial growth at clinically achievable levels.
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susceptible.
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antimicrobial will inhibit bacterial growth at clinically achievable concentrations.
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MIC
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minimal inhibitory concentration. Lowest concentration of antimicrobial that inhibits growth of bacteria
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MBC
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Minimal bactericidal concentration. Concen of an antimicrobial that kills bacteria
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breakpoint
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MIC is used to designate bt susceptible and resistant
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if MIC > breakpoint
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resistant
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if MIC < breakpoint
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susceptible
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reasons for antibiotic overuse
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pt concern: 1)want clear explanat 2)green nasal discharge 3)need to return to work
phys concern 1)pt expects antibiotic 2)diagnostic uncertainty 3)time pressure |
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resistant bacteria can then be transmitted bt pts
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highest risk pts: immunocompromised, hospitialized, invasive devices (central venous catheters)
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give a drug X, it can become resistant to that
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as well as other drugs you haven't even taken
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bacteria are capable of becoming resistant thru several mechanisms, 1 or many may exist in an organism
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multidrug-resistant bacteria oft en have multiple mechanisms, genes encoding resistance may exist on plasmid or chrom
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B-lactamases resistance (on lots of antibiotics)
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confer resistance to some, many, or all beta-lactam antibiotics; may be encoded on chromos or
more potent in gram-negative bacteria -Examples: S. aureus, H. influenzae, N. gonorrhoeae, E. coli, Klebsiella sp. Enterobacter sp, Serratia sp. |
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extended spectrum beta-lactamases
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-Beta lactamases capable of hydrolysing exteended spectrum cephalosporins, penicillins, and aztreonam
-most often associated w E. coli and Klebsiella pneumoniae but spreading to other bacteria -usually plasmid mediated -aminoglycoside,ciprofloxacin, and trimethoprim-sulfamethoxazole resistance often encoded on same plasmid -has become a signif resistance determinate in acute and longterm care facility enteric pathogens |
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Class A Carbapenemases
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-most common is Klebsiella pneumoniae (KPC)
-also seen in E. coli, Enterobacter, Citrobacter, Salmonella, Serratia, Pseudomonas and Proteus spp. -very often w multiple other drug resistance mechanisms, resistance profile similar to ESBL but also carbapenem resistant -became prob in NYC and is being increasingly recognized in MIdAtlantic US -spreading across species to other gramnegatives and enterobacteriaceae -emerging in long tem care facilities |
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Mech of Resistance: Decreased Permeability (changes this so not recognized)
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Pseudomonas spp.;;;; affects many antibiotics including carbapenems
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Mech of Resist: Efflux Pumbs (changes this so not recognized)
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Pseudomonas spp. (multiple antibiotics), tetracylines, macrolides
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Mech of Resist: Target alterat, DNA gyrase (changes this so not recognized)
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-Fluoroquionolines
-many gram negatives, S. pneumoniae |
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Mech of Resist: Target alterat, penicillin binding protein (changes this so not recognized)
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methicillin resistant S. aureus (MRSA); penicillin resistant S. pneumoniae
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Mech of Resist: Target alterat, gram positive cell wall (changes this so not recognized)
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vancomycin; enterococcus spp.
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Mech of resist, Target Alteration, Ribosomes (changes this so not recognized)
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Ribosome: Tetracyclines, Macrolides (S. pneumoniae, Staphylococcus sp., N. gonorrhoeae, enteric gram-negative rods)
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Glycopeptide Resistant S. aureus: Glycopeptide Intermediate Resistance
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-1st reported in Japan
-Vancomycin MIC 8ug/mL -still uncommon -all w/ prolonged vancomycin use due to persistent S. aureus infections (cell walls become bigger) |
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Glycopeptide Resistant S. aureus: Glycopeptide High Level Resistance
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-Vancomycin MIC > 128 ug/ml
-diabetic w/ peripheral vascular disease and chronic renal failure -resistance determinant acquired from Vancomycin-resistant Enterococcus -very uncommon |
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resistant S. pneumoniae increasing
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Resistance increases w/ antibiotic use
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how is resistance most commonly transmitted in gram negative bacteria
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conjugation
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Communiy acquired resistant E. Coli
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-mostly UTIs
-young healthy women in addit to elderly -10 to 20 % now resist to fluoroquinolones -30 to 50% resistant to trimethoprim-sulfamethoxazole -CTX-M Beta-lactamases becoming more common ()cause cephalosporin resistance) |
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Conclusion
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-inapprop and excessive use of antibiotics is a major factor contributing to emerging antibiotic resistance
-determinants of resistance are selected for by antibiotic use - multiple mech exist for bacteria to become resist to antibiotics -antibiotic resist is a prob in outpatient and inpat settings and is a factor in wide variety of infections -antibiotic resist continues to emerge as serious threat to public health |
