Agents Acting on the Cell Wall

Question 1

What classes act on the cell wall?

Answer 1

Beta-lactams:

Penicillins
Cephalosporins
Carbapenems

glycopeptides:
Vancomycin
Teicoplanin
Belomycin (cancer)

Question 2

Penicillins

Answer 2

Penicillin, Amoxicillin, Flucloxacillin, Co-amoxiclav

Question 3

(benzyl) Penicillin (Pinicillin V)

Answer 3

Beta-Lactam - Penicillin

Penicillin is a group of antibiotics which include penicillin G aka Benzylpenicillin (intravenous use), penicillin V (oral), procaine penicillin, and benzathine penicillin (intramuscular use).

–Mainly active against streptococci (gram +ve)

–Most staphlococci now resistant

Question 4

Amoxicillin and co-amoxiclav (Amoxicillin/clavulanic acid)

Answer 4

Beta-Lactan - Penicillins

As with penicillin, Mainly active against streptococci but also some activity against Gram-negatives

Augmentin: contains a combination of amoxicillin and potassium clavulanate, a β-lactamase inhibitor.

Prevents breakdown of drug therefore removing a mechanism of resistance

–Active against staphylococci & streptococci, anaerobes as well as more gram -ve

Question 5

Piperacillin/tazobactam (Tazocin©)

Answer 5

Beta-Lactam - Penicillins

Β-lactamase inhibitor combination Prevents breakdown of drug therefore removing a mechanism of resistance

–Active against staphylococci & streptococci and more effective than Co-amoxiclav vs. Gram -ve incl Pseudomonas aeruginosa

P. aeruginosa is a multidrug resistant pathogen recognized for its ubiquity, its intrinsically advanced antibiotic resistance mechanisms, and its association with serious illnesses – hospital-acquired infections such as ventilator-associated pneumonia and various sepsis syndromes.

Question 6

Flucloxacillin

Answer 6

Unlike other penicillins, flucloxacillin has activity against beta-lactamase-producing organisms such as Staphylococcus aureus as it is beta-lactamase stable as well as streptococci

However, it is ineffective against methicillin-resistant Staphylococcus aureus (MRSA).

Flucloxacillin is more acid-stable than many other penicillins and can be given orally, in addition to parenteral routes. However, like methicillin, it is less potent than benzylpenicillin against non-β-lactamase-producing Gram-positive bacteria.

Question 7

Cephalosporins

Answer 7

Cefaclor, Cefotaxime, Ceftriaxone

• ‘Generations’ with ↑Gneg and ↓Gpos
• ↑broad-spectrum but no anaerobe activity

Cephalosporins are bactericidal and have the same mode of action as other β-lactam antibiotics (such as penicillins), but are less susceptible to β-lactamases.

Cephalosporins disrupt the synthesis of the peptidoglycan layer forming the bacterial cell wall.

Question 8

Ceftriaxone

Answer 8

Beta-lactams - Cephalosoprins
•Cetriaxone has good activity in the CSF so used in meningitis
•Concern over association with C. difficile so less commonly use dnow

Question 9

meropenem (and imipenin)

Answer 9

Beta-Lactams - Carbapenems

A drug of last resort used in life threatening sepsis

–Very broad spectrum (incl anaerobes)

–Active against most (not all) Gram negs

–Generally safe in penicillin allergy, other than anaphylaxis

Question 10

Vancomycin

Answer 10

Glycopeptides

–Active against most Gram pos (not Gnegs)
–Some enterococci resistant (VRE)
–Resistance in staphs rare
–Not absorbed (oral for C. difficile only)
–Therapeutic drug monitoring (TDM) required (narrow therapeutic window)

Question 11

Teicoplanin

Answer 11

Beta-Lactams - Glycopeptides

–Similar activity to vancomycin with MRSA, pseudomembranous colitis and Clostridium difficile
–Easier to administer as IM