Antimicrobials: Affecting Cell Wall

Question 1

Beta-lactam antibiotics

Answer 1

Penicillins, Cephalosporins, Carbapenems, Monobactams

Question 2

Non-Beta Lactams

Answer 2

Bacitracin, Vancomycin, Daptomycin

Question 3

Beta-lactamase inhibitors

Answer 3

Clavulanic acid, Sulbactam, Tazobactam

Beta-lactamase inhibitors often combined with B-lactam antibiotics to prevent bacteria from metabolizing them.

Question 4

Penicillins

Answer 4

Amoxicillin, Ampicillin, Docloxacillin, Indanyl cabenicillin, Methicillin, Nafcillin, Oxacillin, Penicillin G, Penicillin V-K, Piperacillin, Ticarcillin

Question 5

Cephalosporins

Answer 5

1st Generation - Cefazolin, Cephalixin
2nd Generation - Cefaclor, Cefuroxime, Cefoxitin
3rd Generation - Cefdinir, Cefotaxime, Ceftazidime, Ceftriaxone
4th Generation - Cefepime
5th Generation - Ceftavoline

Question 6

Carbapenems

Answer 6

Ertapenem, Imipenem, Meropenem

Question 7

Monobactams

Answer 7

Azetreonam

Question 8

How to beta-lactam antimicrobials work?

Answer 8

They are substrates for transpeptidase enzymes that add them to the end of forming peptidoglycan, preventing further synthesis. Only works on actively dividing bacteria. Only work on organisms with peptidoglycan

Question 9

What must beta lactam drugs to do be effective? 4 things

Answer 9

1. Evade bacterial defenses - lactamase
2. Penetrate outer cell layers to inner cytoplasmic membrane
3. Keep its beta lactam ring intact
4. Bind to transpeptidase (Penicillin binding protein)

Question 10

Natural Penicillins

Answer 10

Penicillin G - active against Gram + Cocci
- Rapidly hydrolied by penicillinase enzymes
- IM or IV
- Short half life
- Narrow Spectrum
- Benzathine penicillin - IM injection with prolonged action used for syphilis
Penicillin V - orally active, but less active than G, used for pharyngitis

Question 11

Aminopenicillins

Answer 11

Ampicillin, amoxicillin

• Better gram - coverage than either Pen G or Pen V
• “Extended spectrum penicillins” - increased activity against H. influenzae, E. coli, Proteus mirabilis, Salmonella, Shigella
• Often combined with B-lactamase inhibitors
• Augmentin = amoxicillin + clavulanate
• Unasyn = ampicillin + sublactam
• Amoxicillin interacts with methotrexate, increases serum levels of methotrexate

Question 12

Prophylaxis for Infective Endocarditis

Answer 12

Amoxicilin is drug of choice

Cephalexin is drug of choice for patients with allergy

Question 13

Penicilllinase-resistant Penicillins

Answer 13

Methicillin, nafcillin, oxacillin, dicloxacillin

• Anti-stahpylococcal penicillins - work against staph and strep, but not enterococci or anaerobes
• First choice against S. aureus and S. epidermidis
• Oxacillin, nafcillin and dicloxacillin given PO, excreted biliary, not renal
• Nafcillin - drug of choice for serious S. aureus infections, not MRSA - “Naf for Staph”

Question 14

Probenecid interactions

Answer 14

Penicillins except nafcillin, oxacillin and dicloxacillin

Probenecid drugs inhibit organic ion transporters in the renal proximal tubules, increase plasma levels of penicillins

Question 15

Antipseudomonal penicillins

Answer 15

Carboxypenicillins - indanyl carbenicllin and ticarcillin
- Wider coverage against gram -, including Pseudomonas aeruginosa. Given IM, IV, NOT PO
Ureidopenicillins - Piperacillin
- Broadest spectrum penicillin, often given with Tazobactam b-lactamase inhibitor as “Zosyn”
Monobactams - Aztreonam
- Unique B-lactam structure, used for patients with IgE penicillin allergy

Question 16

3 Types of Allergic Reactions

Answer 16

Immedate/Acute Onset - 2days, 80-90% of penicillin reactions are this type, generally mild

Question 17

Anaphylaxis

Answer 17

Severe allergic reaction
Causes edema, hypotension, GI disturbance, bronchoconstriction, shock
Life-threatening
Progresses to skin -> eyes, nose, GI -> Respiratory system -> Cardiovascular system

Question 18

Cephalosporins

Answer 18

5 generations
Resistant to many older penicillinases
Renally excreted
Patients with mild allergy can often tolerate
Bactericidal
As generation increases, Gram - activity and b-lactamase resistance increases
5th generation active against MRSA

Question 19

1st Generation Cephalosporins

Answer 19

Not drug of first choice for anything

Cefazolin