E4: Antibiotics Basics

Question 1

How can Antibiotics be classified based on their type of Action?

Answer 1

Antibiotics: Based on effects:

Bactericidal (able to kill microbes)

Bacteriostatic (able to slow the growth of microbes)

Question 2

How can Antibiotics be classified based on the range of antimicrobial activity?

Answer 2

Based on their range of antimicrobial activity:

1. Narrow-spectrum: one of limited number of bacteria
2. Broad-spectrum: G+ MO’s & significant # of G- MO
3. Extended-spectrum: Wide variety of MO’s

Question 3

What are the (6) classes of Antibiotics based on MoAs?

Answer 3

inhibitors of;

1. Folate Synthesis
2. DNA Gyrase
3. RNA Polymerase
4. Protein Synthesis (Ribosomal)
5. Cell wall synthesis
6. Cell membrane

Question 4

What are the (3) methods used to assess microbial sensitivity to drugs?

Which are used to determine the MIC?

Answer 4

Used to determine MIC:

• Broth Dilution test
• E-test method

Used to determine Antibiotic effectiveness:

• Disk diffusion method (Kirby-Bauer test)

Question 5

What is the MIC and how is it determined?

Answer 5

Minimum Inhibitory Concentration (MIC):

• Lowest drug concentration that inhibits microbial growth in vitro

Determined via;

• Broth Dilution test
• E-test method

Question 6

Acquired resistance can occur through which (2) routes?

Answer 6

Acquired Resistance occurs through either;

1. Mutation and selection
2. Transfer of genes encoding resistance factors.
   
   1. Most common mechanism is bacterial conjugation and exchange of plasmids containing resistance (R) factors

Question 7

What are the (3) mechanisms responsible for microbial resistance to a drug?

Answer 7

Mechanisms responsible for microbial resistance to a drug

1. Inactivation of the drug by microbial enzymes
2. Decreased accumulation of the drug by the microbe
3. Reduced affinity of the target macromolecule for the drug

Question 8

Selection of an Antibiotic for a particular infection requires consideration of what?

Answer 8

Host factors:

• Pregnancy
• Drug allergies
• Age
• Immune status
• Presence of concomitant diseases

Drug characteristics:

• Antimicrobial activity
• Pharmacokinetic properties
• Adverse effect profile (Toxicity)
• Cost
• Convenience

Question 9

When are Combinations of Antibiotics typically used?

Answer 9

Combination drug therapy is generally used

• Treatment of mixed infections
• Empiric treatment of serious infections
• Prevention of antibiotic resistance

Exception; In some cases, combination therapy with synergistic drugs is used for the treatment of infections caused by a single microbial species

Question 10

What is Antibiotic Prophylaxis?

When is it used?

Answer 10

Antibiotic prophylaxis:

• The use of antimicrobial therapy to prevent infection complications

Used to prevent;

• Infections during surgical and other invasive procedures
• Transmission of infectious diseases to persons at increased risk