Antimicrobials

Question 1

What is an antimicrobial?

Answer 1

Agent active against microorganisms

Question 2

How are antibacterial agents classified?

Answer 2

• bactericidal (kills it) or bacteriostatic (stops it)
• spectrum- broad vs narrow
• target sites (mechanisms of action)
• chemical structure (antibacterial class-most common classification)

Question 3

What are the ideal features of antimicrobial agents?

Answer 3

Selectively toxic- don’t damage host (or at least as much as they hurt the target organisms)

Few adverse effects

Reach site of infection

Oral/IV formulation

Long half life (infrequent dosing)

No interference with other drugs

Question 4

Name two drugs that can be used to interfer with bacterium’s cell wall?

Answer 4

Penicillin (binds to penicillin binding protein) and vancomycin (block binding site of penicillin binding site)

Question 5

Name a group of dugs that interfer with nucleic acid synthesis

Answer 5

Quinolones

Question 6

What is the action of the drug group quinolones?

Answer 6

They interfer with the neulceic acid synthesis. Stop DNA replication

Question 7

What are the types of resistance?

Answer 7

Intrinsic- no target or access for the drug, never have worked and never will

Acquired-acquires new genetic material or mutates, usually permanent, the drug was susceptible and now its not

Adaptive- the organism responded to a stress, usually reversible, learning to survive

Question 8

What are the 3 mechanisms of antibacterial resistance?

Answer 8

• drug inactivation enzymes- pathogen produces enzymes that can stop the drugs ie beta-lactam drugs can be stopped by beta lactamases
• Altered target- target enzymes has lowered affinity for antimicrobial.eg resistance to meticillin (MRSA)

-altered uptake- lower permeability, dug cant through (often drugs get through cell wall by holes called porins)
Or increased efflux, organism has developed active mechanism for pushing the drug out

Question 9

How can a bacterium become resistant to antibiotics?

Answer 9

Chromosomal gene mutation

Horizontal gene transfer-conjugation

Question 10

What are the 3 mechanisms of horizontal gene transfer?

Answer 10

Conjugation

Transduction - using phases which essentially inject new genetic material

Transformation- collecting free DNA in the surrounding environment (moved through porin)

Question 11

How can you measure antibiotic activity?

Answer 11

Disc sensitivity testing

Question 12

What is the minimum inhibitory concentration?

Answer 12

A minimum concentration of the drug at which it is still effective

There need to be controls

And each tube is doubling in conc, you see whether the antigen has grown or been inhibited.