Wk 6. Antibiotics part 1

Question 1

1. What is selective toxicity? Why is it important?

Answer 1

Injuring a target cell or organism without injuring other cells or organisms in intimate contact with the target. Makes antibiotics safer.

Question 2

2. What is the difference between bactericidal and bacteriostatic?

Answer 2

Bactericidal – kills bacteria

Bacteriostatic – slows growth, phagocytes eliminate bacteria

Question 3

3. What are ranges and chances of drug resistance with narrow-spectrum and broad-spectrum antibiotics?

Answer 3

Narrow: smaller range
less resistance
Broad: larger range
more resistance

Question 4

4. What is acquired resistance? What are four ways bacteria become resistant to antibiotics? How do we lessen the chance for resistance?

Answer 4

Bacteria become less susceptible or lose sensitivity to drug.
1) Reduce drug concentration at sites, 2) Alter drug receptors, 3) Synthesize an antagonist, & 4) Produce drug-metabolizing enzymes.
Treat infection, not colonization, and use correct drug in correct concentration for entire course of therapy.

Question 5

5. What is the difference between the MIC and MBC?

Answer 5

MIC – amount of drug required to halt growth

MBC – amount of drug required to kill 99.9%

Question 6

6. Explain the importance of conjugation. What bacteria are most affected?

Answer 6

Conjugation allows the DNA code for drug resistance to be passed to other bacteria. Gram negative bacteria.

Question 7

7. What are two examples of suprainfections?

Answer 7

Candidiasis (yeast infection), Clostridium difficile infection (CDI) – 3 or more unformed stools in 24 hours with C. difficile or toxin from C. difficile in stools.

Question 8

8. What is the difference between an additive and potentiative effect?

Answer 8

Additive – sum of the effect

Potentiative – greater than the sum of the effects

Question 9

9. How do penicillins kill bacteria?

Answer 9

Disrupts cell wall (inhibits cross-linkages between peptidoglycan strands and lyses cell wall bonds)

Question 10

10. What is the major adverse effect of penicillins?

Answer 10

Allergic reactions

Question 11

11. What are some common signs and symptoms of anaphylaxis and serum sickness to penicillins?

Answer 11

Laryngeal edema, bronchoconstriction, severe hypotension, nausea and vomiting, tachycardia
Rash, hives, pruritis, arthralgias, fever

Question 12

12. Which three penicillins can be taken with food?

Answer 12

Penicillin V, Amoxicillin, Augmentin

Question 13

13. Why is Penicillin G given IM?

Answer 13

Destroyed by gastric acid

Question 14

14. What lab abnormality can occur with Penicillin G or V when administered with potassium supplements?

Answer 14

Hyperkalemia

Question 15

15. What types of enzymes can destroy the penicillin molecule?

Answer 15

General beta-lactamases and penicillinases. Cephalosporinases deactivate cephalosporins.

Question 16

16. What is the advantage of Nafcillin over other penicillins?

Answer 16

Penicillinase-resistant

Question 17

17. Amoxicillin has what kind of bacterial spectrum?

Answer 17

Broad-spectrum

Question 18

18. How does clavulanic acid prevent amoxicillin from being deactivated?

Answer 18

Clavulanic acid inhibits beta-lactamase

Question 19

19. What are other beta-lactam antibiotic groups other than the penicillins?

Answer 19

Cephalosporins, carbapenems

Question 20

20. How do cephalosporins kill bacteria?

Answer 20

Inhibits cell wall synthesis

Question 21

21. Each subsequent generation of cephalosporins show more activity against what type of bacteria? How does each subsequent generation penetrate into the cerebral spinal fluid?

Answer 21

Gram negative bacteria and anaerobes, more resistant to beta-lactamases.
Each subsequent generation is more likely to reach the cerebral spinal fluid.

Question 22

22. What percentage of penicillin-allergic patients will have an allergic reaction to a cephalosporin?

Answer 22

1%

Question 23

23. What is the adverse effect seen with some cephalosporins and alcohol?

Answer 23

Antabuse-like effects: weakness, pulsating headache, chest pain, abdominal cramps

Question 24

24. What is the drug interaction is seen between IV calcium and IV cephalosporins?

Answer 24

Lung and renal precipitates.

Question 25

25. How does vancomycin kill bacteria? What bacteria does it kill?

Answer 25

Inhibits cell wall synthesis. Gram-positive bacteria.

Question 26

26. For what types of infection is vancomycin reserved? How is it given for CDI?

Answer 26

Severe C. difficile infections (CDIs), MRSA, & Staph. Epidermidis. Must be given PO for CDI, because cannot cross between GI tract and bloodstream.

Question 27

27. What are the signs and symptoms of Red Man Syndrome seen with the rapid infusion of vancomycin?

Answer 27

Red rash, hives, flushing, and pruritis on face & upper body. Hypotension, tachycardia. From histamine release, NOT an allergic reaction.

Question 28

28. Creatinine (Cr) is monitored with vancomycin therapy to avoid what? What is an indication for stopping vancomycin?

Answer 28

Renal failure. Stop if Cr rises 50%.

Question 29

29. Aztreonam is used to treat what type of infection? Why?

Answer 29

Gram-negative aerobic bacteria. Only attaches to PBPs on gram-negative aerobic bacteria.