Antibiotics II

Question 0

MOA of penicillins

Answer 0

Bactericidal and time-dependent action.Disrupts cross-linking of the cell wall by irreversible inhibition of transpeptidase.

1) Disinhibition (activation) of autolysins also occurs due to cytosolic accumulation of peptidoglycan precursors; promotes cell wall degradation.
2) Bacterial cell lysis is end result.
3) Most effective against bacteria in the log phase of growth.

Question 1

Beta lactam Antibiotics class

Answer 1

Penicillins

Question 2

Targets of penicillins known collectively as what

Answer 2

Penicillin-binding proteins and include proteins other than transpeptidase

Question 3

3 Mechanisms of resistance of penicillins

Answer 3

1) Inability of lipophilic penicillins to penetrate the G- outer membrane.
2) Acquired mutations in penicillin-binding proteins that lower the binding affinity for the B-lactam.
3) B-Lactamases

Question 4

Standard,narrow spectrum penicillins (2)

Answer 4

Penicillin G, Penicillin V

Question 5

True/False: PenG and Pen V are active against G-»>G+, also effective against anaerobic bacteria.

Answer 5

False: G+»>G-

Question 6

T/F: Pen G is unstable in stomach acid; pen v is acid-stable and thus orally effective

Answer 6

True

Question 7

penicillinase-resistant, narrow spectrum (anti-staph) prototype

Answer 7

nafcillin

Question 8

T/F: Nafcillin is used only against pen G-resistant staph (MSSA) due to altered PBPs with lower binding affinities

Answer 8

True

Question 9

Aminopenicillins, broad spectrum prototype

Answer 9

Amoxicillin, ampicillin

Question 10

Antipseudomonal, extended-spectrum drugs

Answer 10

Ticarcillin, piperacillin

Question 11

What characterizes amoxicillin?

Answer 11

Aditional activity agaisnt G- bacteria due to increased penetration. Susceptible to beta lactamases

Question 12

Characteristics of ticarcillin and piperacillin

Answer 12

Spectrum includes organisms susceptible to aminopenicllins plus Pseudomonas aeruginosa. Given IV for serious hospital acquired G- infections. Susceptible to B-lactamases

Question 13

Fixed-dose combination with B-lactamase inhibitors:

Answer 13

Clavulanic acid-no bactericidal activity of their own; not all B-lactamases are inhibited.

Question 14

T/F: Penicillins have relatively short half-live (30-90 min) and most are orally well absorbed.

Answer 14

False: Not orally well absorbed (diarrhea)

Question 15

Respiratory preparation of penicillin

Answer 15

pen G benzathine

Question 16

Adverse reactions of penicillins

Answer 16

Least toxic Antibiotics.

1) Jarisch-Herxheimer reaction during therapy for syphilis.
2) CNS toxicity (seizures) in pts with high IV doses.
3) Repository prep can be fatal if given IV
4) Amox/Amp can produce rashes not allergy related.
5) Ticarcillin- large IV doses can cause sodium overload

Question 17

First generation cephalosporin

Answer 17

Cefazolin

Question 18

Activity of cefazolin

Answer 18

High activity against G+ MSSA (not MRSA) and strep; less active against G-

Question 19

Second generation Cephalosporin

Answer 19

Cefoxitin

Question 20

Activity of cefoxitin:

Answer 20

More activity against G- bacteria due to higher affinity for PBPs, greater cell envelope penetration and greater resistance to G- B-lactamases, less active than 1st gen against G+ organisms.

Question 21

3rd generation cephalosporin

Answer 21

Ceftriaxone

Question 22

Activity of ceftriaxone

Answer 22

Higher activity against G- and good penetration into CNS. Used for treating meningitis and gonorrhea+empiric chlamydia

Question 23

Fourth generation cephalosporin

Answer 23

Cefepime

Question 24

Activity of cefepime

Answer 24

Highly resistant to B-lactamases and broad antibacterial spectrum; good CNS penetration.

Question 25

Adverse reactions of Cephalosporins

Answer 25

Hypersensitivity, Diarrhea, Potentially nephrotoxic

Question 26

Drug selections of cephalosporins

Answer 26

3rd generation (ceftriaxone) is most widely used.

Question 27

Carbapenems

Answer 27

Imipenem/cilastatin

Question 28

T/F: Imipenem/cilastatin is highly resistant to inactivation by most B-lactamases

Answer 28

True

Question 29

Pharmcokinetics of imipenem/cilastatin

Answer 29

Given parenterally and eliminated predominantly by the kidneys; imipenem is in fixed-dose combination with cilastatin to prevent renal inactivation.

Question 30

Monobactam

Answer 30

Aztreonam- contains a B-lactam ring but it is not fused with a second ring- little cross reactivity for allergies to other B-lactam groups

Question 31

T/F: Aztreonam has a broad spectrum of activity.

Answer 31

False: Narrow spectrum- only against G- aerobic bacteria. Highly resistant to B-lactamases

Question 32

Other cell wall synthesis inhibitors besides B-lactams: Prototype glycopeptide

Answer 32

Vancomycin

Question 33

MOA of vancomycin

Answer 33

Prevents polymerization of cell wall precursors; binds to D-Ala-A-Ala terminus of NAM monomer, blocking addition of NAM-NAG to the NAM-NAG polymer chain (bactericidal).

Question 34

T/F: Vancomycin cannot penetrate G- envelope due to large molecular size; active only against G+ bacteria- S. aureus and S. epidermis

Answer 34

True

Question 35

What is the change that caused VRSA?

Answer 35

Variations in peptide terminus (D-Ala-D-lactate) producing 1000-fold decrease in binding affinity

Question 36

What is VRSA treated with?

Answer 36

Linezolid, daptomycin, or quinupristin/dalfopristin

Question 37

What do you combine Vancomycin with to treat meningitis?

Answer 37

3rd gen cephalosporin (ceftriaxone)

Question 38

What drug has the adverse effects of Ototoxic, "red man syndrome", and Thrombophlebitis with IV infusion?

Answer 38

Vancomycin

Question 39

What drug is a bactericidal phosphenolpyruvate analogue that is used in treatment of uncomplicated G- urinary tract infections

Answer 39

Fosfomycin

Question 40

Drug that inhibits production of murein monomers in the cytosol by inhibiting the synthesis of UDP-NAM from UDP-NAG covalently binds to the active site (-SH group) of the enzyme enolpyruvate transferase

Answer 40

Fosfomycin

Question 41

T/F: Fosfomycin enters the bacterium via a glycerophosphate transporter; mutations to this transporter render the microbe resistant

Answer 41

TRUE

Question 42

What drug is a bactericidal cyclic polypeptide isolated from Bacillus subtilus?

Answer 42

Bacitracin

Question 43

What drug does this MOA belong to: Inhibits bactoprenol dephosphorylation (bactophrenol is a lipid carrier that transfers murein monomers across the inner membrane to the cell wall)

Answer 43

Bacitracin

Question 44

Bacitracin is active against G+/G- bacteria?

Answer 44

G+, much less effective against G-. Acquired resistance is unknown

Question 45

Bacitracin is usually available topically in fixed-dosembination with what 2 drugs?

Answer 45

Neomycin/polymyxin B

Question 46

T/F: Bacitracin is highly nephrotoxic if administered systemically

Answer 46

True