IA. General Microbiology | 8. Antimicrobial drugs that inhibit the cell wall synthesis

Question 1

What are the 2 types of inhibition of cell wall synthesis?

Answer 1

1. Inhibition of peptidoglycans cross-linking (β-lactams)
2. Inhibition of peptidoglycan synthesis (vancomycin)

Question 2

I. Inhibition of peptidoglycans cross-linking (β-lactams)
1. What does Inhibition of peptidoglycans cross-linking (β-lactams) mean?

Answer 2

Inhibit transpeptidation of peptidoglycan chains

Question 3

I. Inhibition of peptidoglycans cross-linking (β-lactams)
2. What are the 5 drugs that can inhibit peptidoglycans cross-linking (β-lactams)?

Answer 3

1. Penicillins
2. Cephalosporins
3. Carbapenems
4. Carbacephems
5. Monobactams

Question 4

I. Inhibition of peptidoglycans cross-linking (β-lactams)
3. What are the features of Penicillins in Inhibition of peptidoglycans cross-linking (β-lactams)?

Answer 4

β-lactams +5membered ring w sulphur
○ Natural Penicillins: Penicillin G,V
○ Enzyme-Penicillins: methicillin, oxacillin (MRSA)
○ Amino-penicillins: ampicillin, amoxicillin
○ Ureido-penicillins: piperacillin, mezlocillin
○ Carboxi-penicillins: carbenicllin

Question 5

I. Inhibition of peptidoglycans cross-linking (β-lactams)
4. What are the features of Cephalosporins in Inhibition of peptidoglycans cross-linking (β-lactams)?

Answer 5

Cephalosporins: β-lactams +6membered ring with sulphur

○ More possibilities for substitution
○ Also against gram negative

○ They have different generation cephalosporins – i.e. cefazolin,
cefuroxim, cefotaxime, cefepime, ceftaroline,…
■ 1st generation is gram + but as move to 4th generation
it becomes gram negative

Question 6

I. Inhibition of peptidoglycans cross-linking (β-lactams)
5. What are the features of Carbacephems in Inhibition of peptidoglycans cross-linking (β-lactams)?

Answer 6

○ Derived from cephalosporins

○ Loracarbef
■ Synthetic β-lactams antibiotic
■ Similar to cefaclor
■ Antibacterial activity resembles II generation cephalosporins

Question 7

I. Inhibition of peptidoglycans cross-linking (β-lactams)
6. What are the features of Carbapenems in Inhibition of peptidoglycans cross-linking (β-lactams)?

Answer 7

○ Widest spectrum
○ Derived from penicillins
○ Imipenem, meropenem, ertapenem
○ Class B β-lactamase = carbapenemase
○ Used for: bacterial meningitis, hospital associated sinusitis and pneumonia, spesis

Question 8

I. Inhibition of peptidoglycans cross-linking (β-lactams)
7. What are the features of Monobactams in Inhibition of peptidoglycans cross-linking (β-lactams)?

Answer 8

Aztreonam
■ Spectrum gram-negative aerobic bacteria, enterobacteriaceae and Pseudomonas aeruginosa
■ Useful in penicillin and cephalosporin allergies

Question 9

II. Inhibition of peptidoglycan synthesis (vancomycin)
1. What are the 2 types of drugs for the Inhibition of peptidoglycan synthesis (vancomycin)?

Answer 9

1. Glycopeptides
2. Polypeptides

Question 10

II. Inhibition of peptidoglycan synthesis (vancomycin)
2. What are the features of Glycopeptides in inhibition of peptidoglycan synthesis (vancomycin)?

Answer 10

○ Vancomycin, teicoplanin
○ Effect: Inhibition of cell wall synthesis via the peptide bond formation
○ Giant molecules → cannot cross the OM of gram-negative bacteria only gram-positive
○ Against: MRSA, C.Difficile

Question 11

II. Inhibition of peptidoglycan synthesis (vancomycin)
3. What are the features of Polypeptides in inhibition of peptidoglycan synthesis (vancomycin)?

Answer 11

○ Bacitracin
○ Mainly against S.aureus and Str. pyogenes, for local treatment (skin infection)
○ By Bacillus licheniformis
○ Inhibit cell wall synthesis by preventing the transport of peptidoglycan precursors through the cytoplasmic membrane
○ Bactericidal to gram-positive bacteria but exhibits little activity against gram-negative