Antimicrobials

Question 1

Penicillins target what part of bacteria?

Answer 1

BACTERIAL CELL WALL Attack
Bactericidal
The b-lactam ring which is required for cell wall synthesis - weakens cell wall = osmotic lysis

Question 2

What do Clavulanic acid and Tazobactam contribute to antibiotic combinations?

Answer 2

They are b-lactamase inhibitors

Question 3

Metabolism of penicillins?

What can block their excretion?

Answer 3

Excreted unchanged in the urine by tubular secretion.

-> can be blocked by – probenecid –

Question 4

Percentage cross reactivity of Penicillins with other B-lactams?

Answer 4

10% cross reactivity

Question 5

Name some Carbapenems

Answer 5

Meropenem and Imipenem

Question 6

How does Carbapenems work

Answer 6

CELL WALL Attack

Also have high affinity to Pencillin Binding Proteins (PBP). Attack different proteins to Pencillins and Cephalosporins on cell wall.

Resistant to B-lactamase.

Question 7

Name a monobactam and what is its activity and cover

Answer 7

Aztreonam, only gram negative cover.

Binds to PBP and is resistant to hydrolysis by most b-lactamases.

Question 8

What differs Cephalosporins from Penicillins?

Answer 8

1. Structurally related to Pencillin except the R group is changed.
2. More stable to staphyloccocal penicillinase but no activity against enterococci.
3. Bind to PBP and prevent transpeptidase activity.

Question 9

Difference between bacteria covered by first and second generation cephalosporins?

Answer 9

First gen (cefalexin/ cefaclor) better gram +ve, with some gram -ve (E. coli, Klebsiella, Proteus) cover.

Second Gen (cefuroxime), slightly less good against G+VE, and better G-VE cover.

Question 10

Glycopeptides examples

How do they work?

Answer 10

CELL WALL SYNTHESIS - BACTERIOSTATIC
Only gram +ve
Bind to peptidoglycan monomer peptides to prevent function of PBP.

Eg. Vancomycin, Teicoplanin

Question 11

Vancomycin Toxicity leads to?

Answer 11

1. OTOTOXICITY - discontinue if tinnitus occurs
2. HISTAMINE RELEASE - hypotension, tachy, widespread rash (RED MAN SYNDROME)
3. PHLEBITIS - diluted preparation required.

Question 12

Which is more potent Vanc or Teicoplanin? Longer duration? Better activity?

Answer 12

Teicoplanin is 2-4 times more potent.

• has longer duration of action and
• more action against streptococci and enteroccoci

Question 13

Which groups of antibiotics attack bacterial protein synthesis?

Answer 13

1. Aminoglycosides - Gent/ Tobra/ Streptomycin
2. Tetracyclines - Doxy, Minocycline
3. Macrolides - Erytho, Clarithro, Azithro
4. Lincosamides - Clindamycin
5. Fusidanes - Fusidic acid

Question 14

Which groups of antibiotics inhibit folate synthesis and metabolism?

Answer 14

1. Sulfonamides - Sulfamethoxazole

2. Trimethoprim

Question 15

Which groups of antibiotics inhibit DNA synthesis?

Answer 15

1. Quinolones - Ciprofloxacin, Levofloxacin
2. Metronidazole
3. Rifampicin

Question 16

Which groups of bacteria inhibit cell wall synthesis?

Answer 16

Penicillins, Carbapenems, Monobactams, Cephalosporins.

Fosfomycin, Vancomycin, Bacitracin, Cycloserine