Antimicrobials

Question 1

Antibiotics that are generally bacteriostatic

Answer 1

Chloramphenicol, Erythromycin/Macrolide, Clindamycin, Sulfonamide, Trimethoprim, Tetracycline, Tigecycline, Linezolid, Quinupristin/Dalfopristin

Question 2

Antibiotics that are generally bactericidal

Answer 2

Vancomycin, Daptomycin, Fosfomycin, Aminoglycosides, Beta-lactams, Tedizolid, Levofloxacin, Rifampin, Metronidazole, Colistin

Question 3

Mechanism of action for Penicillin, Cephalosporin, Carbapenem, Monobactam, Bacitracin

Answer 3

Inhibits enzymes for peptidoglycan synthesis (Cell wall synthesis inhibitors)

Question 4

Mechanism of action for Vancomycin

Answer 4

Binds to peptidoglycan (Cell wall synthesis inhibitor) - Active against GP, MRSA

Question 5

Mechanism of action for Daptomycin

Answer 5

Binds and disrupts cell membrane (Cell membrane synthesis inhibitor) - Active against GP

Question 6

Mechanism of action for Colistin and Polymyxin

Answer 6

Binds and disrupts cell membrane (Cell membrane synthesis inhibitor) - Active against GN

Question 7

Mechanism of action for Aminoglycosides and Tigecycline

Answer 7

Inhibits 30s ribosomal subunit (Protein synthesis inhibitors) - Active against GP and GN

Question 8

Mechanism of action for Chloramphenicol, Macrolides, and Clindamycin

Answer 8

Inhibits 50s ribosomal subunit (Protein synthesis inhibitors) - Active against GP and GN

Question 9

Mechanism of action for Linezolid, Tedizolid, and Streptogramins

Answer 9

Inhibits 50s ribosomal subunit (Protein synthesis inhibitors) - Active against GP

Question 10

Mechanism of action for Fluoroquinolones and Nalidixic acid

Answer 10

Inhibits DNA synthesis (Nucleic acid synthesis inhibitors) - Active against GP and GN

Question 11

Mechanism of action for Nitrofurantoin

Answer 11

Damages DNA directly (Nucleic acid synthesis inhibitor) - Active against GP and GN (UTI only)

Question 12

Mechanism of action for Sulfonamides and Trimethoprim

Answer 12

Interferes with folic acid pathway - Active against GP and many GN bacteria

Question 13

Mechanism of action for Rifampin

Answer 13

Inhibits RNA synthesis - Active against GP and Neisseria meningitidis

Question 14

Antibiotics effective only against GP bacteria

Answer 14

Vancomycin (except VRE, Lactobacillus, Leuconostoc, Pediococcus), Daptomycin, Linezolid, Tedizolid, Streptogramins

Question 15

Antibiotics effective only against GN bacteria

Answer 15

Colistin, Polymyxin

Question 16

Antibiotics effective against both GP and GN bacteria

Answer 16

Penicillin, Cephalosporin, Carbapenem, Monobactam, Bacitracin, Aminoglycosides, Tigecycline, Chloramphenicol, Macrolides, Clindamycin, Tetracycline, Fluoroquinolones, Sulfonamide, Trimethoprim

Question 17

Vancomycin resistance in GN bacteria

Answer 17

All GN bacteria are resistant except Chryseobacterium, Moraxella, and Acinetobacter

Question 18

Colistin and Polymyxin resistance in GP bacteria

Answer 18

Most GP are resistant, while most GN are susceptible

Question 19

Reduced susceptibility of an organism to a particular antimicrobial.

Answer 19

Biologic resistance

Question 20

Occurs when an antimicrobial can no longer be used clinically against a certain bacteria.

Answer 20

Clinical resistance

Question 21

Resistance due to the microorganism’s normal genetic, structural, or physiological state.

Answer 21

Intrinsic resistance

Question 22

Resistance resulting from altered cellular physiology and structure caused by genetic changes.

Answer 22

Acquired resistance

Question 23

Intrinsic resistance: GP bacteria

Answer 23

Aztreonam

Question 24

Intrinsic resistance: GN bacteria, Lactobacilli, Leuconostoc

Answer 24

Vancomycin

Question 25

Intrinsic resistance: Pseudomonas aeruginosa

Answer 25

SXT, tetracycline, chloramphenicol

Question 26

Intrinsic resistance: Stenotrophomonas maltophilia

Answer 26

Imipenem

Question 27

Intrinsic resistance: Klebsiella

Answer 27

Ampicillin

Question 28

Intrinsic resistance: Enterococci

Answer 28

Aminoglycoside, Cephalosporin

Question 29

Intrinsic resistance: Anaerobic bacteria

Answer 29

Aminoglycoside

Question 30

Intrinsic resistance: Aerobic bacteria

Answer 30

Metronidazole

Question 31

Mechanism of resistance: Enzymatic destruction

Answer 31

Beta-lactamase destroys the β-lactam ring of antibiotics; e.g., Staphylococcus resistance to penicillin; Enterobacterales and P. aeruginosa resistance to β-lactam drugs.

Question 32

Mechanism of resistance: Enzymatic modification

Answer 32

Modifying enzymes alter antibiotic binding sites, causing GP and GN resistance to aminoglycosides.

Question 33

Mechanism of resistance: Altered target in bacteria

Answer 33

Mutation in original PBP to PBP2a; e.g., MRSA (PBP -> PBP2a), VRE, VRSA.

Question 34

Mechanism of resistance: Cell wall alteration

Answer 34

Structural changes lead to resistance; e.g., S. pneumoniae and Viridans resistance to β-lactam drugs.

Question 35

Mechanism of resistance: Decreased antibiotic uptake

Answer 35

Porin channel reduction blocks antibiotic entry; e.g., P. aeruginosa resistance to imipenem, GN resistance to aminoglycosides.

Question 36

Mechanism of resistance: Efflux of antibiotic

Answer 36

Bacteria pump the drug out before it binds to the target; e.g., Staphylococcus and Streptococcus resistance to macrolides.