Microbiology Antibiotics IC1
Terminology:
Antibiotics Vs. Antimicrobial
Antibiotics Antimicrobial
Naturally occurring agent produced by a Any drug that inhibits or kills a bacterium,
microbe that inhibits or kills another. virus, fungus, etc.
Usually anti-bacterial agent.
Therapy
Empiric Prophylactic
Treatment of an infection with antibiotics before Administration of antibiotics to prevent an
specific culture has been reported or obtained. infection.
As before surgeries.
Anti-bacterial Spectrum
DEF: The range of activity of an anti-microbial against bacteria.
Broad Narrow
Def Anti-bacterial drugs that can inhibit a wide Drugs that are active only against limited
range of Gram+ve and Gram-ve bacteria. range of bacteria.
Pros Poly microbial Minimal disruption of normal flora
Unknown aetiology
Cons Super infection; Cl. Difficile Not suitable for blind therapy
Example Cefapime Penicillin G
Gram +ve Gram +ve only
Gram -ve
Anaerobes
Bacteriostatic Vs. Bactericidal
Bacteriostatic Bactericidal
Def The level of anti-microbial activity that The level of anti-microbial activity that kills
inhibits the growth of an organism. the organism.
Determination In vitro, testing a standardized [] of an In vitro, testing a standardized [] of an
organism against a series of anti- organism against a series of anti-microbial
microbial dilutions. dilutions.
Measurement Minimum Inhibitory Concentration (MIC): Minimum Bactricidal Concentration (MBC):
Lowest conc. That inhibits the growth of Lowest conc. That kills 99.9% of the
an organism. organism population.
MOA Halt growth. Kills bacteria.
Irreversible
Example Macrolides Penicillin G
Tetracyclins Gentamicin
RMSH 2012
, Microbiology Antibiotics IC1
Time dependant Vs. Concentration dependant
Time Dependant Concentration Dependant
Increase amount of time the antibiotics bind to High conc. At the binding site which eradicates the
microorganism. microorganism.
t>MIC Peak>MIC
Penicillin Aminoglycosides
Cephalosporin Fluroquinolones
Carbapenem Ketolides
Monobactams
Antibiotics Combination:
WHY? WHEN?
Broaden anti-microbial spectrum for empiric therapy.
Treatment of polymicrobial infections.
Prevent emergence of resistant organisms during therapy. (TB)
Achieve synergistic killing effect. (treatment of infective endocarditis)
TYPES..
Antibiotics Synergism Antibiotics Antagonism
Combination of antibiotics that have enhanced Combination of antibiotics in which the activity of
bactericidal activity when tested together one interferes with the activity of the other.
compared with the action of each of them The sum of activity when together is less than the
separately. sum when each is tested separately.
Aminoglycoside + -lactams -lactam + -lactam
e.g. Pseudomonas infections
Ampicillin + Gentamicin Enterococcal Induction of -lactamase by one agent renders the
endocarditis other agent ineffective.
Penicillin + Gentamicin Viridans streptococcal What is -lactamase?
endocarditis An enzyme that hydrolyzes the -lactam ring in
Vancomysin + Staphylococcal -lactam class of antibiotics thus making Ab
Gentamycin bacteremia ineffective.
RMSH 2012
Terminology:
Antibiotics Vs. Antimicrobial
Antibiotics Antimicrobial
Naturally occurring agent produced by a Any drug that inhibits or kills a bacterium,
microbe that inhibits or kills another. virus, fungus, etc.
Usually anti-bacterial agent.
Therapy
Empiric Prophylactic
Treatment of an infection with antibiotics before Administration of antibiotics to prevent an
specific culture has been reported or obtained. infection.
As before surgeries.
Anti-bacterial Spectrum
DEF: The range of activity of an anti-microbial against bacteria.
Broad Narrow
Def Anti-bacterial drugs that can inhibit a wide Drugs that are active only against limited
range of Gram+ve and Gram-ve bacteria. range of bacteria.
Pros Poly microbial Minimal disruption of normal flora
Unknown aetiology
Cons Super infection; Cl. Difficile Not suitable for blind therapy
Example Cefapime Penicillin G
Gram +ve Gram +ve only
Gram -ve
Anaerobes
Bacteriostatic Vs. Bactericidal
Bacteriostatic Bactericidal
Def The level of anti-microbial activity that The level of anti-microbial activity that kills
inhibits the growth of an organism. the organism.
Determination In vitro, testing a standardized [] of an In vitro, testing a standardized [] of an
organism against a series of anti- organism against a series of anti-microbial
microbial dilutions. dilutions.
Measurement Minimum Inhibitory Concentration (MIC): Minimum Bactricidal Concentration (MBC):
Lowest conc. That inhibits the growth of Lowest conc. That kills 99.9% of the
an organism. organism population.
MOA Halt growth. Kills bacteria.
Irreversible
Example Macrolides Penicillin G
Tetracyclins Gentamicin
RMSH 2012
, Microbiology Antibiotics IC1
Time dependant Vs. Concentration dependant
Time Dependant Concentration Dependant
Increase amount of time the antibiotics bind to High conc. At the binding site which eradicates the
microorganism. microorganism.
t>MIC Peak>MIC
Penicillin Aminoglycosides
Cephalosporin Fluroquinolones
Carbapenem Ketolides
Monobactams
Antibiotics Combination:
WHY? WHEN?
Broaden anti-microbial spectrum for empiric therapy.
Treatment of polymicrobial infections.
Prevent emergence of resistant organisms during therapy. (TB)
Achieve synergistic killing effect. (treatment of infective endocarditis)
TYPES..
Antibiotics Synergism Antibiotics Antagonism
Combination of antibiotics that have enhanced Combination of antibiotics in which the activity of
bactericidal activity when tested together one interferes with the activity of the other.
compared with the action of each of them The sum of activity when together is less than the
separately. sum when each is tested separately.
Aminoglycoside + -lactams -lactam + -lactam
e.g. Pseudomonas infections
Ampicillin + Gentamicin Enterococcal Induction of -lactamase by one agent renders the
endocarditis other agent ineffective.
Penicillin + Gentamicin Viridans streptococcal What is -lactamase?
endocarditis An enzyme that hydrolyzes the -lactam ring in
Vancomysin + Staphylococcal -lactam class of antibiotics thus making Ab
Gentamycin bacteremia ineffective.
RMSH 2012
