Principles of Antimicrobial Therapy

Question 1

Cell wall synthesis inhibitors

Answer 1

Beta-lactam antibiotics
Vancomycin
daptomycin
bacitracin and fosfomycin

Question 2

Protein synthesis inhibitors

Answer 2

Tetracyclines (30S)
Glycylcyclines 
- Tigecycline (30S)
aminoglycosides (30S)
macrolides (50S)
chloramphenicol (50S)
clindamycin (50S)
streptogramins
- Quinupristin, Dalfopristin
linezolid (23S of 50S)

Question 3

Drugs that affect Nucleic acid synthesis

Answer 3

Fluoroquinolones
Sulfonamides
Trimethoprim

Question 4

Miscellaneous and urinary antiseptics

Answer 4

Metronidazole

Nitrofurantoin

Question 5

What is a bacteriostatic drug?

Example?

Answer 5

reversible inhibition of growth. Helps individuals immunity in combating pathogen

e. g. Tetracycline
- once stopped bacterial growth reoccurs

Question 6

Bactericidal

Answer 6

irrversible inhibition of growth

Question 7

Selective toxicity

Answer 7

Ability to injure or kill an invading microorganism without harming host cells

Question 8

Postantibiotic effect

Answer 8

Killing action continues once drug plasma levels are below measurable levels (very effective-longer efficacy)

Question 9

Examples of Broad spectrum drugs

when should you use these and what are they prone to?

Answer 9

Tetracycline
chloramphenicol
Prone to increased risk of resistance
Don’t want use these unless in serious infection

Question 10

Narrow spectrum drug example

Answer 10

Isoniazid (anti TB drug- very specific)

Question 11

Extended spectrum drug

Answer 11

Ampicillin

Amoxicillin

Question 12

Minimal inhibitory concentration (MIC)

Answer 12

Lowest concentration of ab that prevents visible growth.

- measured by broth or tube dilution method or disc sensitivity

Question 13

Minimal Bactericidal Concentrtion (MBC)

Answer 13

lowest conc. of ab that results in a 99.9% decline in colony count after overnight broth dilution incubations

Note: the MBC of a truly bactericidal agent is equal or just slightly higher than MIC

Question 14

Combination therapy

Mechanism of synergism

Answer 14

Sequential blockade (e.g. trimethoprim + Sufamethaoxazole)
Blockade of drug-inactivating enzymes (eg clavulanic acid + amoxicillin)
Enhanced drug uptake ( eg. increased permeability to aminglycosides after B-lactam tx.)

Question 15

Antimicrobial Chemoprophylaxis

- Rules:

Answer 15

• Should always be directed toward a specific pathogen.
• No resistance should develop.
• Use should be of limited duration (1 off dose).
• Conventional therapeutic dose should be employed.
• Should only be used in situations of documented drug efficacy.