Ch.20

Question 1

What is a semi-synthetic antibiotic?

Answer 1

• chemically altering structure of antibiotics to make new compounds in a lab
• its semi synthetic because base of compund is a naturally occuring living microbe

Question 2

How does toxicity correlate to therapeutic index and how is it calculated?

Answer 2

• Toxicity is relative and expressed as therapeutic index
• Calculated as the lowest dose toxic to patient divided by dose used for therapy

Question 3

If an antibiotic has a high therapeutic index, what does this mean?

Answer 3

• high therapeutic index = less toxic

Question 4

What does it mean when a drug is bacteriostatic?

Answer 4

• chemicals inhibit bacterial growth

Question 5

What does it mean to be a broad spectrum vs narrow spectrum antibiotic?

Answer 5

• Broad-spectrum antibiotics affect a wide range of microrganisms
  – treat acute life-threatening diseases –> especially when no time to culture for identification
• Narrow-spectrum antibiotics affect limited range
  – Requires identification and susceptibility of pathogen
  – Less disruptive to microbiome
  – know more about pathogen –> narrow spectrum

Question 6

Which type (broad or narrow spectrum) antibiotics most likely to disrupt the normal microbiota? How come?

Answer 6

• broad spectrum antibiotics because it disrupts more of microbiome

Question 7

What does the half-life of an antimicrobial medication indicate?

Answer 7

• Half-life of medication is time it takes for serum concentration to decrease by 50%
• Dictates frequency of doses required to maintain effective level in body

Question 8

What is the synergistic effect when administering antimicrobial medication? Why are medications administered synergistically?

Answer 8

• Some medications enhance one another
• causes the total effect of two drugs to be greater than the sum of the individual effects of each drug

Question 9

What is an antagonistic effect when administering antimicrobial medications?

Answer 9

Some medications interfere with others

Question 10

What is selective toxicity? What allows for selective toxicity in a medication?

Answer 10

• Selective toxicity: causes greater harm to microbes than to human host
• medication attacks pathogen by targeting the differences between the cell structure and composition of a bacterial cell vs structure of human host so it leave the human host cell by itself

Question 11

What kinds of antibiotics are inhibited by Beta-lactamases? How do beta-lactamases inhibit these antibiotics?

Answer 11

• Pencillin, cephalosporisins, carbapenems, monobacterams
• breaks β-lactam ring; destroys activity of antibiotic

Question 12

What part of the bacteria do protein synthesis inhibitors typically act on?

Answer 12

ribosomes

Question 13

How do Sulfonamides inhibit microorganisms?

Answer 13

• competive inhibitors: competitively inhibit enzyme needed and sulfamides bind to enzyme instead
• Inhibit many Gram-positives and Gram-negatives

Question 14

How do bacteria become resistant to antibiotics? What are the mechanisms?

Answer 14

1. medication-inactivating enzymes: bacteria produces enzymes that interfrere w/ drug
2. alteration of target molecule: structural changes to prevent binding
3. decreased uptake of medication: changes in gram-negative membrane
4. increased eliminiation of medication: efflux pumps remove compunds