Antimicrobials

Question 1

Modes of action of antimicrobials

Answer 1

Cell wall
Protein synthesis 
DNA synthesis 
Cytoplasm or cell membrane 
Metabolic pathways e.g. folic acid

Question 2

Inhibit cell walls

Answer 2

Beta lactams - Penicillin, Cephalosporins and Carbepenems

Glycopeptids- Vancomycin

Question 3

Inhibition of Protein synthesis

Answer 3

Aminoglycosides- Gentamycin
Macrolides-Erythromycin
Tetracyclines

Question 4

Inhibit DNA or RNA synthesis

Answer 4

Fluroquinolones- Ciproflaxacine

Rifampicin

Question 5

Activity of Vancomycin/Glycopeptide

Answer 5

Inhibits cell wall synthesis.
Bulky substance binds to pentapeptide precursor but now this cannot be transported to the wall due to the bulkiness it added and therefore the peptidoglycan wall cannot be made.
Bactericidal

Question 6

What is vancomycin good for?

Answer 6

Gram positive but nephrotoxicity.
Good for resistant staph infections e.g. MRSA
People allergic to beta lactams
C-difficile patients

Question 7

Activity of beta lactams

Answer 7

Mimics d-ala d-ala on precursor and attaches to the transpeptidase (penicillin binding protein) enzymes and inactivates it from making the peptidoglycan cell wall
Bactericidal

Question 8

What is beta lactams good for?

Answer 8

For penicillins - Gram positive bacteria, some gram negatives
Enterobacterales and pseudomonas for cephalosporins
Carbepenems are for reserves

Question 9

Activity of aminoglycans

Answer 9

Bactericidal
Binds on the 30s ribosome subunit
Stops initiation and early termination and wrong incorporation of the AA

Question 10

What is gentamycin or aminoglycans good for

Answer 10

Good but nephrotoxicity

Gram positives, Enterococci, enterobacterales and extended pseudomonas

Question 11

Activity of tetracycline

Answer 11

Binds to 30s and prevents and inhibits protein synthesis

Bacteriostatic

Question 12

Application of tetracyclines

Answer 12

Chelates calcium and causes discolouration of teeth and therefore not used

Question 13

Activity and application of Macrolides/ erythromycins

Answer 13

Binds to 50s to stop translation and elongation
Bacteriostatic
Good for gram positives and Neisseria and Haemophilus

Question 14

Activity of fluoroquinolones/ciprofloxacin

Good for?

Answer 14

Stops enzymes DNA gyrase seems which supercoils the double stranded and stops Topoisomerase IV which stops the tension when supercoiling. Therefore DNA strand breaks.
Bacteriacidal
Good for gram negatives including P. Aeruginosa

Question 15

Amphotericin for cell membranes

Answer 15

Forms pore on the cell membrane to cause cell lysis
But can be toxic
Good for fungal infections

Question 16

Activity of Sulphonamide and septrin and Application

Answer 16

Inhibit folic acid synthesis
Bacteriostatic
Used for UTI