Flashcards in Antibiotics Deck (22):
Antimicrobial therapy relies on what principle tenet?
What contributes to antibiotic resistance?
Genetic mutation and/or acquisition of genetic elements from other bacteria carrying resistance genes
What are the mechanisms of antibiotic resistance?
1. Breakdown2. Chemical modification 3. Alteration4. Altered permeability, decreased influx or increased efflux5. Lack of target
What is bacteriostatic activity?
Level of antimicrobial activity that INHIBITS growth
What is the MIC?
1. Minimum inhibitory concentration2. Lowest concentration of antibiotic that inhibits growth
What is bactericidal activity?
Level of antibiotic that KILLS
What is the MBC?
1. Minimum bactericidal concentration2. Lowest concentration of antibiotic that kills 99.9%
What tests can give you the MIC?
1. Disk diffusion assay (circles)2. E-test (leaves)3. Broth culture
What are characteristics of cell wall active antibiotics?
1. Disrupts peptidoglycan synthesis2. Effective against actively dividing bacteria
What are characteristics of membrane active antibiotics?
1. Disrupts or interferes with membrane integrity / synthesis2. Effective against resting and actively dividing bacteria
How do B-lactams inhibit cell wall synthesis?
1. Bind to PBPs or other transpeptidases (cover active serine site)2. Prevents addition of another peptidoglycan sheet to growing wall
How is B-lactam resistance conferred?
1. Mutation so that B-lactams can no longer bind to active serine site of PBPs2. Pumped out of periplasmic space3. Altered permeability involving porins
How does vancomycin inhibit bacterial growth?
1. Recognizes and binds to two D-ala residues on peptide chains2. Prevents peptide chains from interacting properly with transpeptidase3. Cross links cannot be formed
How are bacteria resistant to vancomycin?
D-ala residue replaced by a D-lactate
How does bacitracin inhibit bacterial growth?
1. Inhibits cycling of peptidoglycan to outer leaflet2. Double phosphorylated bactoprenol builds up and cannot be used by cell
What are characteristics of tetracyclines?
1. Bacteriostatic2. Bind 30S subunit3. Broad spectruum
What are characteristics of aminoglycosides?
1. Generally bactericidal2. Bind 30S subunit3. Oxygen dependent4. Effective only against aerobic organisms
What are characteristics of macrolides?
1. Bind 50S ribosome2. Used as an alternate for individuals with penicillin allergy
What are characteristics of quinolones?
1. Bactericidal2. Inhibits DNA replication, recombination, and repair
What are characteristics of rifampin and rifabutin?
Bind to DNA dependent RNA polymerase and inhibits initiation of RNA synthesis
What are characteristics of metronidazole?
Reduced by bacteria = toxic compounds that damage DNA