Lecture 12: Antibiotics Part 1

Question 1

Antibacterials are produced by organisms to do what?

Answer 1

To eliminate bacterial competitors and predators

Question 2

How do selectively toxic antibiotics work?

Answer 2

• Target cell structure, enzymes, or pathways that are unique to bacteria
• Don’t harm human cells

Question 3

How do broad spectrum antibiotics work? In what situation would they be given?

Answer 3

• Inhibit/kill many species/classes of bacteria
• Can kill Gram-positive and Gram-negative bacteria
• Given first when infection is suspected but ID is not available

Question 4

How do narrow spectrum antibiotics work?

Answer 4

• Inhibit/kill a few species/classes of bacteria
• Often correlated with cell wall type
• Typically kills Gram-positive OR Gram-negative bacteria

Question 5

Why are Gram-negative bacteria typically more resistant to antibiotics?

Answer 5

Because of their restrictive double membrane

Question 6

Antibiotics can be bacteriostatic and/or bactericidal. What does bacteriostatic vs. bactericidal mean?

Answer 6

1. Bacteriostatic: inhibits bacterial cell division and can be reversed when the antibiotic is removed
   - Requires the immune system to clear the bacteria
2. Bactericidal: kills the bacteria and will not grow even in the absence of the antibiotic

Question 7

Define minimum inhibitory concentration (MIC).

Answer 7

Lowest concentration of an antimicrobial that will inhibit the detectible growth of a microorganism after overnight incubation

Question 8

_____ will determine if a particular bacterium is resistant, intermediate, or susceptible to an antibiotic.

Answer 8

MIC breakpoints

Question 9

Where can you find guidelines for breakpoints and antibiotics?

Answer 9

Clinical and Laboratory Standards Institute (CLSI) documents

Question 10

What parts of bacteria could antibiotics target?

Answer 10

Question 11

Give an overview of the history of antibiotics.

Answer 11

Question 12

How are antibiotics prescribed (i.e. what things to consider)?

Answer 12

• Not all drugs have breakpoints and not all drugs work for all sites
• What antibiotic to report and when to report are determined by CLSI and hospital/clinical lab
• Hospitals don’t carry all antibiotics
• Patient allergies and tolerance to the antibiotic

Question 13

What is antibiotic stewardship?

Answer 13

The effort to measure and improve how antibiotics are prescribed by clinicians and used by patients

Question 14

Antibiotics are responsible for what fraction of emergency department visits for adverse drug effects?

Answer 14

1 out of 5

Question 15

Antibiotics are the most common cause of emergency department visits for what in children under 18?

Answer 15

Adverse drug events

Question 16

What are 5 reasons why antibiotics can be toxic?

Answer 16

Question 17

What is the most prescribed antibiotic in the US?

Answer 17

β-lactams

Question 18

What are β-lactams defined by?

Answer 18

β-lactam ring

Question 19

What do β-lactams target? How?

Answer 19

Target cell wall
- Bind to the penicillin binding protein (PBP) and block peptide cross-linking

Question 20

What are the 5 classes of β-lactams?

Answer 20

1. Penicillins
2. Cephalosporins
3. Carbapenems
4. Monobactams
5. Clavams

Question 21

What distinguishes the different types of β-lacatams?

Answer 21

R group

Question 22

What is vancomycin? What does it target and how?

Answer 22

• Glycopeptide
• Targets cell wall
• Binds to the acyl-D-ala-D-ala terminal group and blocks cross-linking

Question 23

What type of bacteria is vancomycin effective against?

Answer 23

Effective against Gram-positive bacteria

Question 24

Why is vancomycin not effective against Gram-negative bacteria?

Answer 24

Cannot cross the outer membrane of Gram-negative bacteria