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Microbiology Antimicrobial Susceptibility Testing
Antimicrobials
75
Microbiology
Graduate
12/12/2012

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Cards

Term
Antibiotic therapy
Definition
use of chemical compounds to treat diseases caused by microorganisms
Term
Antibiotic
Definition
produced by organism
Term
Antimicrobial agent
Definition
synthetic compounds
Term
Bactericidal
Definition
Kills organism
Term
Bacteriostatic
Definition
inhibit growth to allow immune system to fight off bacteria
Term
Combination therapy
Definition
additive, indifferent, synergistic, and antagonistic
Term
Additive
Definition
each kills a certain amount of bacteria
Term
indifferent
Definition
each kills the same amount of bacteria
Term
synergistic
Definition
work together to kill more bacteria
Term
antagonistic
Definition
antibiotic interefere with one another
Term
Factors affecting Antimicrobial activity
Definition
environment and concentration
Term
environment
Definition
state of metabolic activity (microorganisms are dormant or live), distribution of drug in body tissue, location of organisms, interfering substances (food, alcohol)
Term
concentration
Definition
absorption (depends on route of administration), distribution (varies within tissues), and variability of concentration (dosing schedule to keep in therapeutic range)
Term
Intrinsic resistance
Definition
known, no susceptibility testing
Term
Aminoglycosides do not work on anaerobic bacteria or Enterococcus
Definition
because anaerobes do not use oxidative phosphorylation which takes up the Aminoglycosides
Term
Aztreonam (beta lactam) doesn’t work on gram positive bacteria
Definition
because it doesn’t have the protein binding site
Term
Vancomycin doesn’t work on gram negative rods
Definition
because of their complicated cell wall thorough which complex vancomycin cannot penetrate
Term
SXT, tetra and chloramphenicol doesn’t work on P. aeruginosa
Definition
because it lacks the means of uptake and the antibiotics can never reach the concentration to work
Term
Ampicillin doesn’t work on Klebsiella
Definition
because Klebsiella produces beta lactamase which destroys ampicillin before it reaches the binding site
Term
Metronidazole doesn’t work on aerobic bacteria
Definition
because they cannot reduce
Term
All cephalosporins cannot be used against Enterococcus
Definition
because they do not have the penicillin binding sites
Term
Lactobacilli and leuconostoc
Definition
do not have vancomycin binding site
Term
S.maltophilia produces an enzyme
Definition
that destroys imipenem
Term
Acquired resistance (5)
Definition
• Enzymatic degradation/modification of agent
• Decreased uptake
• Altered agent
• Circumvention of consequences of antimicrobial action
• Uncoupling of antibiotic-target interactions
Term
emergence of resistance (4)
Definition
• Old genes to new hosts
• New genes
• Mutations of old genes to become more potent
• Intrinsically resistant opportunistic bacteria due to inappropriate and widespread use of antibiotics
Term
Mechanisms of action (5)
Definition
• Effect cell wall integrity
• Effect cell membrane structure and function
• Inhibit protein synthesis
• Inhibit essential metabolites
• Interefere with nucleic acid metabolism
Term
Beta-Lactams
Definition
cell wall integrity, inhibit cell wall synthesis by binding to transpeptidase (penicillin binding protein), bactericidal in actively growing organisms
Term
Penicillins
Definition
beta lactam ring with one place for modification, differ in R group
Term
Penicillin G
Definition
strep, clost, aerobic GPR
Term
Ampicillin
Definition
strep, clost, aerobic GPR and some enterococci
Term
Methicillin
Definition
act against beta lactamase, staph
Term
Ticarcillin, pipercillin
Definition
pseudomonas
Term
Cephalosporins
Definition
two places for modification, 4 generations
Term
1st generation cephalosporins
Definition
GP cocci (not Enterococcus) anaerobic cocci
Term
2nd generation cephalosporins
Definition
GP cocci (not Enterococcus) anaerobic cocci and Enterobacteriaceae, ceftetan: bacteroides
Term
3rd generation cephalosporins
Definition
lose GP cocci, GNRs, pseudomonas, penetrate CNS
Term
4th generation
Definition
enhanced enteric
Term
Monobactams
Definition
no secondary ring, no GPC, GPR or anaerobes
Term
Carbapenems
Definition
extended spectrum of activity, aerobic, anaerobic strep, enterics, pseudomonas
Term
Penicillin and Cephalosporin resistance due to
Definition
enzymatic destruction- beta lactamase, altered target-altered penicillin binding protein, decreased uptake- change in porin number and character
Term
Glycopeptides
Definition
vancomycin and daptomycin,
Term
vancomycin and daptomycin
Definition
gram positive, Inhibit the 2nd stage of cell wall synthesis, bactericidal, for gram positive only
Term
resistance to glycoproteins due to
Definition
Resistance due to altered target-cell wall precursor structure to decrease binding, and target overproduction- excess peptidoglycan
Term
Polymyxins
Definition
bind to cell membrane phospholipids, destroys active transport and membrane permeability barrier, bactericidal,
Term
polymyxins effective against
Definition
gram – aerobic bacilli (pseudomonas and Serratia)
Term
Toxicity of polymyxins
Definition
neurotoxin and poor distribution
Term
Aminoglycosides
Definition
bind to 30s ribosomal unit, bactericidal
Term
aminoglycoside Resistance due to
Definition
altered target-deficiency of ribosomal receptor, enzyme modification- enzymatic destruction of drug and decreased uptake- lack of permeability to drug molecule
Term
aminoglycoside toxicity
Definition
ototoxic (hearing loss) and nephrotoxic (kidney
Term
Streptomycin
Definition
aminoglycoside, TB
Term
kanamycin
Definition
aminoglycoside, topical antibiotic
Term
gentamicin/tobramycin/amikin
Definition
gram + (not strep), gram – pseudo, not anaerobes, does not penetrate CNS
Term
Tetracyclines
Definition
inhibit protein synthesis by reversibly binding to 30S subunit, Bacteriostatic
Term
Tetracyclins Resistance due to
Definition
efflux system, altered/protected ribosomal target, enzyme inactivation
Term
Macrolides
Definition
: attach to receptor of 50S subunit, interefere with translocation reactions, Bacteriostatic, works on gram positive and a few gram negative (Legionella, Moraxella, and campy)
Term
macrolides resistance due to
Definition
efflux (pump drug out of cell before target binding), altered target (enzymatically alter ribosomal target to reduce binding)
Term
Clindamycin
Definition
attach to 50S subunit and interferes with translocation, Bacteriostatic, works on aerobic gram + and anaerobic bacteria (bacteroides)
Term
Chlororamphenicol
Definition
reversible binding of 50S subunit blocks bond formation, Bacteriostatic
Term
Chlororamphenicol Resistance due to
Definition
by Chlororamphenicol acetyltransferase, decreased uptake
Term
Chlororamphenicol toxicity
Definition
problems with RBC maturation, and rarely aplastic anemia
Term
Sulfonamides
Definition
interefere with folic acid pathway by competitively inhibiting bacterial dihydropteroate synthetase
Term
Trimethoprim
Definition
: interferes with folic acid pathway by competitively inhibiting bacterial dihydrofolate reductase
Term
Sulfonamides and Trimethoprim
Definition
• Bacteriostatic
• Used in combination against gram + and many gram – but no pseudomonas
• Resistance due to altered enzyme targets
Term
resistance of Sulfonamides and Trimethoprim
Definition
altered enzyme targets
Term
Rifampin
Definition
binds DNA dependent RNA polymerase
Term
Rifampin Resistance due to
Definition
change in RNA polymerase target
Term
Rifampin used on
Definition
mycobacterium, never taken alone always in combination (only alone for prophylaxis
Term
Quinolones
Definition
all come from nalidixic acid, block DNA gyrase, bactericidal, used against gram + and gram –
Term
resistance of Quinolones
Definition
decreased uptake-alteration in outer membrane to reduce uptake or activation of efflux pump or altered target, change in DNA gyrase subunits to decrease FQ binding
Term
Metronidazole
Definition
disrupts DNA by making it unstable, must be partially reduced to become active so only works in anaerobic organisms, bactericidal
Term
Effects on cell wall integrity
Definition
Beta lactams, glycopeptides
Term
Effects on cell membrane structure and function
Definition
polymyxins
Term
Inhibition of protein synthesis
Definition
Aminoglycosides, tetracyclines, and Macrolides
Term
Inhibition of essential metabolites
Definition
sulfonamides
Term
Interference with nucleic acid metabolism
Definition
quinolones
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