Chapter 20: Antimicrobial Medications + Antibacterial Drugs

Question 1

How do antimicrobial medications work?

Answer 1

• usually act by interfering with the growth of microorganisms

Question 2

Why are antimicrobial medications unlike disinfectants? (2)

Answer 2

• must work inside a patient
• selective toxicity

Question 3

What is selective toxicity?

Answer 3

• damages pathogens withut harming host

Question 4

What are the spectrums of antimicrobial activity?

Answer 4

narrow and broad

Question 5

What is the narrow spectrum of antimicrobial activity?

Answer 5

• drug effective against limited range of organisms
  ex. Penicillin G affects only gram + bacteria

Question 6

What is the broad spectrum of antimicrobial activity?

Answer 6

• affects a wide range of organisms

Question 7

What is an advantage to the broad spectrum of antimicrobial activity?

Answer 7

• useful when identity of pathogen is not known

Question 8

What is a disadvantage to the broad spectrum of antimicrobial activity?

Answer 8

• bad for the normal microbiota

Question 9

Why is tetracycline part of the broad spectrum?

Answer 9

affects both gram + and - bacteria

Question 10

What are bacteriocidal antibacterial drugs?

Answer 10

kills bacteria

Question 11

What are bacteriostatic antibacterial drugs?

Answer 11

• prevents the growth of bacteria

Question 12

What are the 4 types of Antibacterial drug types?

Answer 12

1. Inhibition of cell wall synthesis
2. Protein synthesis inhibitors
3. Injury to plasma membrane
4. Inhibitors of nucleic acid synthesis

Question 13

how do antibacterial drugs inhibit cell wall synthesis? (3)

Answer 13

• Target peptidoglycan
• excellent selective toxicity
• most frequently used antibacterial drugs

Question 14

What type of antibacterial drugs are used to inhibit cell wall synthesis? (2)

Answer 14

• beta lactams:
  penicillin - G, amoxicillin, ampicillin, methicillin
  cephalosporins - cephalothin, cefepime
• Bacitracin
• Vancomycin

Question 15

How do beta lactams work?

Answer 15

• prevent production of peptidoglycan
• thus growing cells lyse
  note the beta lactam ring is present in chemicals (4 ring)

Question 16

How do bacteria resist penicillins? (3)

Answer 16

• produce penicillinases (beta lactamases)
• so semisynthetic penicillins developed
  ex. methicillin, desgined to resist penicillinases, but bacteria have adapted (methicillin-resistant S. aureus MRSA)

Question 17

What is bacitracin? (3)

Answer 17

• narrow spectrum antibiotic
• active against gram +
• toxic to humans

Question 18

How is bactracin used?

Answer 18

only used externally
ex. polysporin

Question 19

What is vancomycin? (2)

Answer 19

• very narrow spectrum but effective against S. aureus
• used as a last resort against MRSA

Question 20

What has the use of vancomycin led to? (3)

Answer 20

• vancomycin resistant enterococci (VRE)
• opportunistic pathogens cause nosocomial infection
• can transfer resistance genes to other bacteria

Question 21

Mechanically, how to beta lactams work? This is from the diagram on slide 4

Answer 21

• they competitively inhibit enzymes that help form cross-links between adjacent glycan chains