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64 Cards in this Set
- Front
- Back
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when do we perform AST?
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1. AST is performed on organisms that exhibit resistance to commonly used drugs
2.Perform AST only if organism was seen in GS with neutrophils or is from a normally sterile body site |
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AST---what is the purpose of Standardization?
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1.Optimize bacterial growth conditions
2.Optimize antibiotic integrity and activity 3.Assure reproducibility and consistency of results |
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principle of Kirby-Bauer Disk diffusion testing?
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1. Disk impregnated with antimicrobial agents are placed on agar surface seeded with pure lawn of isolate
2. Disk begin to diffuse to establish a concentration gradient 3. Growth is inhibited at a certain antibiotic concentration leaving a clear zone around disc Zone of inhibition is measured in millimeters |
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kirby-bauer media?
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Mueller-Hinton agar
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when do we perform AST?
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1. AST is performed on organisms that exhibit resistance to commonly used drugs
2.Perform AST only if organism was seen in GS with neutrophils or is from a normally sterile body site |
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why do we incubate kirby-bauer agar facing down?
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To prevents moisture dripping on agar surface
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AST---what is the purpose of Standardization?
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1.Optimize bacterial growth conditions
2.Optimize antibiotic integrity and activity 3.Assure reproducibility and consistency of results |
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principle of Kirby-Bauer Disk diffusion testing?
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1. Disk impregnated with antimicrobial agents are placed on agar surface seeded with pure lawn of isolate
2. Disk begin to diffuse to establish a concentration gradient 3. Growth is inhibited at a certain antibiotic concentration leaving a clear zone around disc Zone of inhibition is measured in millimeters |
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kirby-bauer media?
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Mueller-Hinton agar
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why do we incubate kirby-bauer agar facing down?
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To prevents moisture dripping on agar surface
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what could cause false resistance of Kirby-Bauer tesing?
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1. Old media
2. Depth of agar too thick 3. Inoculum too high 4.Delay in adding disc >15min 5. Disk is not concentrate enough 6.Delay in reading Zone sizes |
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what could false sensitivity of Kirby-Bauer testing?
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1.Cation concentration decreased
2. Depth of agar too thin 3. Inoculum too low 4. Disk is too concentrated |
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what is Minimum Inhibitory Concentration(MIC)?
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Lowest concentration of an antibiotic that inhibits visible growth
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Minimum Bactericidal Concentration (MBC)?
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Lowest concentration of antibiotic that yields no viable growth
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what is tolerance and how to calcalate it?
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1. When an organism requires a much higher dose of drug to kill it than to inhibit it.
I2. ndicated by a large difference between the MIC and the MBC Tolerance = MBC/MIC 32 |
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what is a test that combine disk diffusion and MIC?
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E test
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enzyme that orgs acquire to break down the beta lactam ring of Penicillin?
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Beta lactamase
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what test use to detect Beta lactamase?
what color is positive result? |
Nitrocefin disk (Cefinase disk)
When the beta-lactam ring of the cephalosporin is hydrolyzed by the organism, a deep pink color is produced |
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Schlicter Test?
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1. Antibiotic dilution: patient serum with drug concentration (peak and trough)
2. Peak: highest antibiotic concentration (~30 to 90 min after administration) Trough:Lowest antibiotic concentration (right before administering the next dose) |
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the test used to test the effectiveness of using combination therapy against a single isolate?
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Synergy Testing
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describe 3 scenarios in synergy testing--Synergy, indifference and Antagonism?
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1) Synergy
Activity of combination of drugs > than each drug alone 2) Indifference Activity of combination is no better or worse than each drug alone 3) Antagonism Activity of combination of drugs is worse than each drug alone |
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who discovered “miracle drug” penicillin?
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Alexander Fleming
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Bacteriostatic and Bactericidal?
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Bacteriostatic: inhibits further growth of organism
Bactericidal: kills the organisms |
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antimicrobial agents that inhibit cell wall synthesis?
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1.Penicillins
2.Cephalosporins 3.Vancomycin 4.Bacitracin 5.Carbepenems 6.Monobactams |
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Agents that affect membrane permeability?
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1.Polymixins
2.Antifungal agents |
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Agents that affect protein synthesis, the Transcription inhibitor?
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Rifampin
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Agents that affect protein synthesis, the Translation inhibitors?
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1. Aminoglycosides
2. Chloramphenicol 3. Tetracyclines 4. Macrolides |
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Trimethoprim/ Sulfamethoxazole
Sulfonamides Anti-TB drugs these drugs are anti-_______drug |
Antimetabolites
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how do Beta lactam agents Inhibit Cell Wall Synthesis?
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1. Beta lactam agent contains a beta-lactam ring that bind to PBP ( Penicillin Binding Proteins)
2. PBP is an enzyme group in bacteria responsible for producing and maintaining cell peptidoglycan layer 3. Blocks cell wall synthesis and trigger processes that lead to autolysis and death of cell |
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Penicillin classified as: five of them
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1. Natural penicillins
2.Semisynthetic penicillins/Antistaphylococcal Penicillins 3.Extended spectrum penicillins 4.Augmented penicillins 5.Antipseudomonas penicillins |
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1.Natural Penicillins-active against _____ and _____?
2. examples of natureal Penicillin? |
1.Group A strep and Neisseria meningitidis
2.Benzylpenicillin G (Penicillin G) Phenoxymethyl (Penicillin V) |
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which Penicillin actively against Antistaphylococcal penicillins and used for penicillin-resistant Staph?
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Semisynthetic Penicillins
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Semisynthetic Penicillins includes___? (five of them)
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1.Methicillin
2.Oxacillin 3.Nafcillin 4.Cloxacillin 5.Dicloxacillin |
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Extended Spectrum Penicillin includs:
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Ampicillin
Amoxicillin |
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what is augmented penicillin?
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2 beta-lactam agents combine, one binds to beta-lactamase enzyme while the other acts against the organism
ex:Amoxicillin + clavulanic acid (Augmentin) |
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_______penicillin tht Synergistic against P. aeruginosa when combined with aminoglycosides ?
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Antipseudomonas Penicillins
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what it mean Penicillin Resistance?
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Organisms have developed the beta-lactamase enzyme and it destroys the beta-lactam ring of antibiotic
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Agents are grouped in “Generations” based on their spectrum of activity?
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Cephalosporins
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FIrst generation of cephalosporins has Good activity against Gram Positives
Poor activity against Gram Negatives Agents include: |
1.Cefazolin
2.Cephalothin 3.Cephalexin 4.Cefaclor |
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second generation of cephalosporins?
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More activity against gram negatives, valuable in treatment of H. influenzae
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second genration agents inculde:
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1.Cefuroxime (Ceftin/Zinacef)
2.Cefotetan 3.Cefoxitin 4.Cefamandole |
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Third generation?
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1. Good activity against gram negatives
2. Good for identified beta-lactamase producers H. influ., or M. cat., N. gonorrhoeae, N. meningitidis |
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Third generation includewhich agents?
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1.Ceftriaxone (Rocephin)
2 Cefotaxime (Claforan) 3 Ceftazidime (Fortaz) |
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fourth generation?
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1.Good activity against Pseudomonas
2.Some activity against enterics |
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agents included in fourth generation?
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Cefipime
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what organisms are resistance to cephalosporins?
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ESBL (Extended Spectrum Beta Lactamase Producers)
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ESBL producers include:
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1.K. pneumoniae ,
2 K. oxytoca 3 E. coli 4Enterobacter sp. |
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How to identify ESBL producers?
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Any gram negative bacilli (Enterobacteriaceae) that tests R to ceftazidime (King of Cephalosporins)
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which penicillin that has the most effective against gram + and MRSA?
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Glycopeptide/ Vancomycin
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the toxicity of vacomycin?
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renal and auditory
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mechanism of Aminoglycosides that inhibit protein synthesis?
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1.Bind to 30S ribosomal subunits and interfere with protein synthesis (elongation)
2. Bactericidal |
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aminoglycosides agents include:
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Gentamicin
Tobramycin Amikacin Kanomycin |
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Macrolide is bactericidal or bacteristatic?
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bacteristatic
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macrolide agents?
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Erythromycin
Clarithromycin Azithromycin Quinupristin/dalfopristin-newer |
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Chloramphenicol is bacteristatic and highly against _________and _______?
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Gram – and Gram +
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which antibiotic affect bone and teeth?
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Tetracyclines
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an antibiotic inhibit RNA synthesis?
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Rifampin
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antibiotic cause Gray baby syndrome?
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Chloramphenicol
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the greater MIC, the more ______the organism is to the drug?
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resistant
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Fluoroquinolones (Quinolones) agents?
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Ciprofloxacin
Levofloxacin Gatifloxacin Moxifloxacin Gemifloxacin |
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The bility to detect MRSA may be enhanced by?
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using Mueller-Hinton agar with 4% NaCl
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standarized tesing for the Kirby-Bauer agear disc diffusion antimicrobial susceptibility test include:
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1. use of Mueller-Hinton meida
2. standard inoculum size 3. incubation at 35 celcius 4. incubation in ambient air |
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The modified Hodge test is used to determine?
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carbepenemase production from K.pneumoniae
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the "D" test performed by the Kirby Bauer method with clindamycin and erythromycin discs is used to determine?
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inducible clindamycin resistance in Stphylococci and Streptococci
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