Antibiotics

Question 1

Fosfomycin

Answer 1

Cell wall inhibitor - non-Beta-lactam. Blocks PDG synthesis.
Broad spectrum
Use: single dose for uncomplicated UTI (E. coli & faecalis). Resistance develops with multiple doses.

Question 2

D-cycloserine

Answer 2

Cell wall inhibitor - non-beta-lactam. Blocks PDG synthesis.
Broad spectrum
Oral, good CNS penetration, active form in urine.
Use: 2nd line in M. tuberculosis treatment.
Toxicity: serious CNS SE, dose related, reversible.

Question 3

Bacitracin

Answer 3

Cell wall inhibitor - non-beta-lactam. Blocks PDG synthesis.
Narrow spectrum (Gram (+), Neisseria, T. Pallidum)
Uses: Topical only. Skin & eye infections. Combine w/ Polymyxin B (membrane inhibitor)
AE: Nephrotoxicity

Question 4

Vancomycin

Answer 4

Cell wall inhibitor - non-beta-lactam. Blocks PDG x-linking.
Narrow spectrum: Gram (+)
Use: serious Gram (+) infections, MRSA, S. pneumoniae. Synergistic with Aminoglycosides.
Rapid bactericidal for dividing cells - except Enterococci.
IV administration; slowly.
Toxicity: Red Man Syndrome: quick administration - histamine release. Ototoxic, nephrotoxic.
Resistance: VRE, VRSA

Question 5

Penicillin G (Pen G)

Answer 5

Cell wall inhibitor - Beta-lactam. Bactericidal.
Acid labile, parenteral administration; IM.
Repository forms (Procaine & Benzathine) are longer release than IM.
Use: Gram (+). Non-penicillinase producing microbes.
AE: allergies, Stevens-Johnson Syndrome (erythema, rashing, edema, can be deadly)

Question 6

Penicillin V (Pen V)

Answer 6

Cell wall inhibitor - Beta-lactam. Bactericidal.
Acid stabile. Oral administration (65% absorption vs 30% Pen G)
Use: Gram (+). Non-penicillinase producing microbes.
AE: allergies, Stevens-Johnson Syndrome (erythema, rashing, edema, can be deadly)

Question 7

Oxacillin

Answer 7

Cell wall inhibitor - Beta-lactam. Bactericidal.
Penicillinase-resistant. Anti-staphylococcal.
Use: Staph, Strept. Not good against MRSA (PBP with lower affinity for drug)
AE: hepatitis at high doses.

Question 8

Amoxicillin

Answer 8

Cell wall inhibitor: Beta-lactam - Extended spectrum penicillin. Bactericidal. Destroyed by beta-lactamase.
Acid stable, oral, not affected by food
Use: Gram - bacilli, non-lactamase producing. Mixed infections. Prophylaxis for endocarditis

Question 9

Carbenicillin

Answer 9

Cell wall inhibitor: Beta-lactam - Extended spectrum penicillin. Bactericidal. Carboxypenicillin.
IV - serious systemic infection. Pseudomonas, Klebsiella

Question 10

Piperacillin

Answer 10

Cell wall inhibitor: Beta-lactam - Extended spectrum penicillin. Bactericidal. Ureidopenicillin.
IV.
Use: serious systemic infection. Pseudomonas, Klebsiella

Question 11

Beta-lactamase inhibitor

Answer 11

Clavulanic Acid, Sulbactam.
No Abx activity. Analogs of the drugs. Bind to Beta-lactamase - suicide inhibitors.
Synergistic with extended spectrum penicillins.

Question 12

Imipenem

Answer 12

Carbapenem. Beta-lactam.
Broadest activity of all B-lactam drugs. Penetrate outer membrane of Gram - bacteria
IV, renal metabolism and inactivation. W/ Cilastatin, inhibits metabolism of Imipenem.
Use: second line for serious infections
Not useful for MRSA, VRE. May induce B-lactamase expression (antagonistic to pen, ceph)

Question 13

Aztreonam

Answer 13

Beta-lactam. Monobactam.
Binds PBP, relatively resistant to B-lactamase.
No significant cross reactivity with pen***
Use: limited to Gram -, Pseudomonas
Not anaerobes, Gram +

Question 14

Daptomycin

Answer 14

Cell membrane agent - membrane depolarization
IV administration.
Similar to Vancomycin, but can treat MRSA, VRE

Question 15

Tetracycline, Doxycycline, Minocycline

Answer 15

Tetracyclines
Inhibit 30s subunit.
Antagonizes penicillin. Decreased absorption with cations, increased pH.
BROAD spectrum, superinfetcion.
Use: Acne, Rickettsia, good CNA penetration
Discoloration of teeth

Question 16

Tigecycline

Answer 16

Derivative of minocycline
Inhibitor of 30s subunit. Binds with higher affinity than tetra cyclines.
Use: some MRSA, tet-resistant

Question 17

Gentamicin

Answer 17

Aminoglycosides
Protein Synthesis Inhibitor (30s) Irreversible
Only ones that are bactericidal
Significant PAE (post antibiotic effect)
Use: Gram - bacteria. Combination with penicllin, vancomycin (help get aminoglycosides into cells)
Slow resistance.
Not well absorbed - IV, or IM only. Poorly distributed. Concentrate in inner ear (irreversible), renal cortex.

Question 18

Spectinomycin

Answer 18

Protein Synthesis Inhibitor (30s)
Structurally related to aminoglycosides.
Bacteriostatic.
Use: mostly Gram -; ***anti-biotic resistant gonorrhea, MRSA

Question 19

Azithromycin, Clarithromycin, Erythromycin***

Answer 19

Macrolides
Protein Synthesis Inhibitor - bind irreversibly to 50s subunit.
Bacteriostatic. High doses, alkaline pH.
Combine competitively to same spot as other drugs
Narrow spectrum
Use: Gram +, clarithro- azithro- more effective against anaerobe. Alternative to Penicillin
Resistance: rapid. Cross resistance with many other protein synthesis inhibitors. (MLS-type b resistance: methylases modify bacterial ribosome, unable to bind drug)
Erythromycin is not acid stable.
Wide distribution: even go to abscesses. Poor penetration to CNS.
AE: GI effects*, hepatotoxicity, anorexia
Azithromycin: unique, has no interaction with Cyp450

Question 20

Telithromycin

Answer 20

Ketolide
Protein Synthesis Inhibitor. Derivative of Erythromycin. Bacteriostatic. Binds 50s subunit at 2 sites. Reduced resistance.
Use: community acquired respiratory tract infection.
AE: exacerbation of myasthenia gravis

Question 21

Chloramphenicol

Answer 21

Protein Synthesis Inhibitor - reversibly to 50s, near clindamycin and macrolides
Bacteriostatic. Oral
Use: Broad spectrum. Anaerobic, gram -
Wide distribution,
AE: Resistance (gram -, staph. aureus). Gray Baby Syndrome … infants cannot metabolize drug.
Hepatic metabolism Cyp450, prolongs half-life

Question 22

Synercid = Quinupristin + Dalfopristin

Answer 22

Streptogramin
Protein Synthesis Inhibitor - 50s. Combination makes them bactericidal.
Use: MRSA, VRE (gram +)

Question 23

Linezolid

Answer 23

Binds to unique site of ribosome - 23s. No cross reaction.
Bacteriostatic
Use: MRSA, VRE

Question 24

Clindamycin

Answer 24

Lincosamide
Binds 50s subunit. MLS type b resistance
Wide distribution, bone included.
Use: osteomyelitis, abscesses, MRSA, severe Group A

Question 25

Mupirocin

Answer 25

Topical for use in treating impetigo from MRSA