Abx MOA

Question 1

Beta-lactams

Answer 1

Inhibition of cell wall synthesis via inhibition of cross-linking of peptidoglycan in the cell wall, leading to autolysis and cell death. The beta-lactam ring of the drug forms a covalent bond with the proteins essential for cell wall synthesis (PCN-binding proteins [PCPs]).
Results in rapid bactericidal activity against sensitive bacteria.

Question 2

Fluoroquinolones

Answer 2

Inhibition of DNA gyrase (bacterial topoisomerase), leading to DNA strand breaks and rapid bactericidal activity

Question 3

Macrolides and Ketolides

Answer 3

Binding at the 50S ribosomal subunit and blockade of bacterial protein synthesis leads to bacteriostatic effects

Question 4

Aminoglycosides

Answer 4

Binding at the 30S ribosomal subunit and blockade of bacterial protein synthesis leads to bactericidal activity

Question 5

Glycopeptides

Answer 5

Inhibits cell wall synthesis by binding to D-ala-D-ala residues of peptide cell wall precursors.
Bactericidal against nearly all G+ bacteria.
Vanc. is bacteriostatic against enterococci and is therefore used often in combination with an aminoglycoside against these organisms.

Question 6

Cyclic Lipopeptides

Answer 6

Binds o components of the cell membrane and causes rapid depolarization, inhibiting intracellular synthesis of DNA, RNA, and proteins (bactericidal activity)

Question 7

Oxazolidinones

Answer 7

Inhibits bacterial protein synthesis by binding to bacterial 23S ribosomal RNA of the 50S subunit. This prevents the formation of a functional 70S initiation complex that is essential for the bacterial translation process.
Bacteriostatic against enterococci and staphylococci; bacteriostatic against most strains of streptococci.

Question 8

Streptogramins

Answer 8

Binds to 50S ribosomal subunit and inhibits bacterial protein synthesis

Question 9

Tetracyclines and Glycylcyclines

Answer 9

Binding at the 30S ribosomal subunit and blockade of protein synthesis leads to bacteriostatic activity

Question 10

Nitroimidazoles

Answer 10

Bioactivated to toxic metabolite by nitroreductase, an enzyme found in significant quantity only in anaerobic organisms (bactericidal)

Question 11

Lincosamides

Answer 11

Binding to the 50S ribosomal subunit and blockade of bacterial protein synthesis leads to bacteriostatic activity

Question 12

Fosfomycin

Answer 12

Inhibits bacterial cell wall synthesis by preventing the production of the building blocks of peptidoglycan

Question 13

Nitrofurans

Answer 13

Not well characterized

Question 14

Folate antagonists

Answer 14

All: inhibit steps in the folate biosynthesis pathway, depleting the pool of nucleosides and leading to inhibition of DNA synthesis in susceptible organisms.
SMX: inhibits dihydrofolic acid formation from para-aminobenzoic acid.
TMP: inhibits dihydrofolic acid reduction to tetrahydrofolate.
Bactrim: when used separately that are bacteriostatic. When combined they are bactericidal