Antibiotics Flashcards
Bacteriostatic
inhibits growth but doesn’t kill
Examples of bacteriostatic antibiotics
tetracyclines, macrolides, antimetabolites
Tetracyclines
target bacterial ribosome (70S)
bind 30S subunit
broad spectrum
Macrolides
target bacterial ribosome (70S)
binds to 50S subunit
used as an alternate for individuals with penicillin allergy
Antimetabolities
target folate metabolism
Bactericidal
kills the bacteria
used during invasive infections
Examples of bactericidal antiboitics
B-lactams Vancomycin Aminoglycosides Quinolones Rifampin/rifabutin Metronidazole
B-lactam
inhibit cell wall synthesis
Binds beta lactamases and prevents enzymatic inactivation of b-lactam
Vancomycin
attacks cell wall
- In sensitive bacteria it recognizes and binds to two D-ala residues on the end of peptide chains
- Present the peptide chains, prevents them from interacting properly with transpeptidase
- Cross links can’t be formed
Aminoglycosides
targets bacterial ribosome (70S)
binds to 30S subunit
oxygen-dependent
effective only against aerobic organisms
Quinolones
inhibits DNA replication, recombination and repair
Rifampin, rifabutin
binds to DNA depending RNA polymerase and inhibits initiation of RNA synthesis
Metronidazole
reduced by bacteria
toxic compounds that damage DNA
Sensitive infection
Infection may be treated with the dosage regimen of an antimicrobial agent recommended
Intermediate infection
Infection may be treated in body sites where the drug are physiologically concentrated or when a high dosage of drug can be used
resistant infection
Resistant isolates are not inhibited by the usually achieved concentrations of the antimicrobial
General mechanisms of antibiotic resistance
Breakdown of an antibiotic Chemical modification of an antibiotic Alteration of the target Altered permeability, decreased influx or increased efflux Lack of target
Empiric therapy
treatment while waiting for lab results (broad)
Targeted therapy
refined treatment (narrow spectrum)
How to prevent antibiotic resistance
only prescribe for bacterial infections
Maintain a therapeutic dose for a prolonged period of time
Combinatorial therapy
Antibiotic prophylaxis
Who might need antibiotic prophylaxis
immunocompromised pts
surgical pts
those with exposure to certain high risk pathogens
Minimum inhibitory concentration
lowest conc. of antibiotic that inhibits growth
minimum bactericidal concentration
lowest conc. of antibiotic that kills 99.9% of bacteria
Kirby Bauer Test
relies on antibiotic impregnated discs that are dropped onto a bacteria growth media that has bacteria spread across the agar surface. You measure the zone of clearing (zone of inhibition) around the disc. In doing this you are measuring the MIC.
