Antibacterial Agents II Flashcards Preview

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Flashcards in Antibacterial Agents II Deck (14)
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1
Q

Chemistry of Penicillin and Cephalosporin

A

Penicillins: beta lactam ring + thiazolidine ring
Cephalosporins: beta lactam ring + dihydrothiazine ring

2
Q

Mechanism of Action

A

Beta-lactams bind to penicillin-binding proteins (PBPs)
Inhibit transpeptidase activity
Prevent cross-linking of peptidoglycan strands (thus inhibiting final step in cell wall synthesis)
Important role of autolytic enzymes (degrade existing cell wall)

Beta-lactams disrupt the balance between peptidoglycan assembly & degradation. The antibacterial effect results from both inhibition of cell wall synthesis & destruction of the existing cell wall by autolysins

3
Q

Bacterial Cell Wall of Gram Negative Bacteria

A

Hydrophilic beta lactams can enter through porins

Lipophilic beta lactams can enter through the membrane

NAG NAM units make peptidoglycans

Beta Lactamase: located in periplasmic space and beta lactams may enter, but have to get through the beta lactamases to get to PBPs, so protect the cell

4
Q

Group 1 Penicillins

A

Natural
Types G and V for gram +, gram - cocci, spirochetes, and anaerobes that lack beta lactamases
G = IV > oral
V = oral

Resistance: strep pneumoniae (low affinity PBPs), staph aureus, and Neisseria gonorrhoeae

5
Q

Group 2 Penicillins

A

Penicillinase resistant
Methicillin, nafcillin, oxacillin, and dicloxacillin
Methicillin - no longer used because of toxicity

Resistant to destruction by narrow spectrum beta lactamases from staph aureus and MSSA

Not effective for MRSA due to mecA

6
Q

Group 3 Penicillins

A

Extended Spectrum
Ampicillin, Amoxicillin, Ticarcillin, and Pipercillin

Ampicillin and Amoxicillin: similar to Pen G, but better gram - rod coverage

Ticarcillin and Pipercillin: more gram - rods from amoxicillin including pseudomonas

All are subject to degradation by beta lactamases

7
Q

First Generation Cephalosporins

A

Cefazolin (IV) and Cephalexin (oral)
Resistance to beta lactamases and high potency

Used for gram + cocci, some gram - cocci and rods

8
Q

Second Generation Cephalosporins

A

Subgroup 1: Cefuroxime and Cefaclor
Subgroup 2: Cefotetan and Cefoxitin

Used for: same as 1st generation, but more gram - rods and cocci
PeCK - proteus, E. coli, and klebsiella

9
Q

Second Generation Subgroup 1

A

Cefuroxime and Cefaclor

H. influenzae, but not Bacteriodes fragilis or Serratia

10
Q

Second Generation Subgroup 2

A

Cefotetan and Cefoxitin

B. fraglis, some Serratia, but less active for H. influenzae

11
Q

Third Generation Cephalosporins

A

Ceftriazone, Cefotaxime, and Ceftazidime

Used for: same pathogens as 1st and 2nd generation + more gram - coverage such as Neisseria species and rods (Serratia, Klebsiella, etc.)

Pseudomonas responds to Ceftazidime

12
Q

Fourth Generation Cephalosporins

A

Cefepime
More resistant to some beta lactamases than 3rd generation, some extended spectrum beta lactamases (ESBLs) and chromosomally encoded, inducible type 1 beta lactamases (ex. Amp-C)
Multi-drug resistance pneumococci
Excellent activity for gram - rods, P. aeruginosa, and enterobacter

13
Q

Beta Lactamase Inhibitors

A

Clavulonic Acid, Sulbactam, and Tazobactam

Use with penicillin agents, not alone

Example: Clavulonic Acid + Amoxicillin
Clavulonic acid prevents the breakdown of amoxicillin by inhibiting the beta lactamases and allowing for amoxicillin to work

14
Q

Ceftriazane and Cefotaxime

A

Third Generation Cephalosporins

Used for initial (empirical) tx of meningitis in adults and children
Exhibit some activity for penicillin resistant pneumococci in combination with 2nd drug, good activity for gram - pathogens involved in meningitis, and community acquired pneumonia (CAP)