Antibiotics-Cell Wall Agents

Question 1

Penicillin G

Answer 1

• Penicillins – usually IM, can be IV
• Acid-labile (broken down in stomach) – inhibit PBPs and PDG cross-linking - bactericidal
• Allergies, dose dependent neurotoxicity and seizures, Stevens Johnson syndrome
• Gram + and some gram – cocci (Strep pneumonia, Staph, Neisseria, Clostridium, Treponema pallidum)

Question 2

Penicillin V

Answer 2

• Penicillins - oral
• Acid stable – inhibit PBPs and PBG cross-linking - bactericidal
• Allergies, Stevens Johnson syndrome
• Gram + and some gram – cocci (Strep pneumonia, Staph, Neisseria, Clostridium, Treponema pallidum)

Question 3

Oxacillin

Nafcillin

Answer 3

*B-lactamase resistant
Penicillinase-resistant
*Acid stable, food interferes with absorption, give parenterally - inhibit PBPs and PBG cross-linking - bactericidal
*Hepatitis at high doses
*Penicillinase-producing Staph and Strep (NOT FOR MRSA)

Question 4

Amoxicillin

Ampicillin

Answer 4

• Extended spectrum
• Destroyed by B-lactamases – acid stable, amoxicillin > ampicillin absorption - inhibit PBPs and PBG cross-linking - bactericidal
• Non-lactamase gram- bacilli (E. coli, H. influenza, Salmonella, Shigella), prophylaxis against bacterial endocarditis

Question 5

Piperacillin

Answer 5

• Extended spectrum – parenteral administration
• Destroyed by B-lactamases - inhibit PBPs and PBG cross-linking - bactericidal
• Serious systemic infections (Klebsiella and Pseudomonas) – combo with aminoglycoside to prevent resistance

Question 6

Ticarcillin

Answer 6

• Extended spectrum – parenteral administration
• Destroyed by B-lactamases - inhibit PBPs and PBG cross-linking - bactericidal
• Anti-pseudomonal, rarely used alone

Question 7

Clavulanic acid
Sulbactam
Tazobactam

Answer 7

• B-lactamase inhibitor
• B-lactamase suicide inhibitors
• Used in fixed concentrations with extended spectrum penicillins

Question 8

Cefazolin

Answer 8

• Cephalosporin – 1st generation – oral, IV, IM
• Bind to PBPs and inhibit cell wall synthesis – best acid stability
• Allergy
• Broadest spectrum against gram + cocci (surgical prophylaxis), gram – bacilli

Question 9

Cefuorxime

Answer 9

• Cephalosporin – 2nd generation – oral, IV, IM
• Bind to PBPs and inhibit cell wall synthesis
• Allergy, Antabuse effect (sensitivity to alcohol)
• Activity against anaerobes – diverticulitis, sinusitis, peritonitis, otitis media

Question 10

Cefotaxime

Answer 10

• Cephalosporin – 3rd generation – oral, IV, IM
• Bind to PBPs and inhibit cell wall synthesis
• Allergy, Antabuse effect (sensitivity to alcohol)
• Anti-pseudomonal and pneumococcal, serious gram – infections (meningitis, pneumonia, gonorrhea) – children and infants

Question 11

Cefepime

Answer 11

• Cephalosporin – 4th generation – oral, IV, IM
• Bind to PBPs and inhibit cell wall synthesis
• Allergy
• Anti-pseudomonal, high resistance to B-lactamases (good for Enterobacter and penicillin resistant Strep)

Question 12

Imipenem

Answer 12

• Carbapenem – parenteral administration
• Has B-lactam ring, binds more efficiently with PBPs, penetrate outer membrane of gram - bacteria
• GI effects, super infections, neurtoxicity - Renal metabolism and inactivation (administered with cilastatin – inhibits dehydropeptidases)
• Broadest activity of all B-lactam drugs, NOT for MRSA or VRE – 2nd line for serious nosocomial infections

Question 13

Aztreonam

Answer 13

• Monobactam – IM or IV use
• Binds PBPs, relatively resistant to B-lactamases – drug penetrates inflamed CNS
• No significant cross-reactivity with
• Narrow spectrum, limited to gram- aerobes (Pseudomonas), not gram + or anaerobes – use for gram – UTIs, lower RTIs, and systemic infections

Question 14

Bacitracin

Answer 14

• Peptidoglycan synthesis inhibitor
• Depletes lipid carrier for PDG synthesis – poorly absorbed
• Severe nephrotoxicity
• Topical only! – Narrow spectrum (gram +, Neisseria, T. pallidum) – skin and ophthalmologic infections (combination with polymyxin B)

Question 15

Cycloserine

Answer 15

• Peptidoglycan synthesis inhibitor
• Structural analog of D-alanine, blocks step 2 – good CNS penetration
• VERY TOXIC – serious CNS effects, dose related, reversible
• Broad spectrum – restricted second-line M. tuberculosis

Question 16

Daptomycin

Answer 16

• Cell membrane agent – IV administration
• Membrane depolarization, bactericidal
• Myopathy
• Narrow spectrum –serious gram+ infections, penicillin resistant S. pneumonia, VRE and MRSA

Question 17

Fosfomycin

Answer 17

• Peptidoglycan synthesis inhibitor
• Structural analog of PEP, blocks step 1 – well absorbed and distributed, rapid resistance
• Few adverse effects (diarrhea, vaginitis)
• Broad spectrum – single dose oral treatment of uncomplicated UTIs (E. coli and E. faecalis)

Question 18

Vancomycin

Answer 18

• Peptidoglycan synthesis inhibitor – IV administration (SLOW), rarely oral (poor absorption, excellent distribution
• Inhibits growth of strand by binding to D-ala dimer – blocks cross-linking by binding substrate – rapidly bactericidal for dividing cultures (except static in enterococci)
• too fast IV administration – histamine release – HTN, tachycardia, flushing), ototoxicity, nephrotoxicity

VRE and VRSA resitant
*Narrow spectrum – gram + microbes (DRUG OF CHOICE FOR MRSA) – serious gram+ infections, penicillin resistant S. pneumonia, combination with aminoglycosides (synergistic)