lesson eight

Question 1

two antiparasitic agents

Answer 1

1. anti-protozoan drugs
2. anti-helminthic drugs

Question 2

quinine and derivatives for malaria

Answer 2

increasing resistance of malaria to the drugs

Question 3

antifungal agents

Answer 3

• fungi are eukaryotic organisms
• most successful agents affect the plasma membrane of fungi- which contains ergosterol instead of cholesterol
• all drugs have some toxicity (kidney)
• most common drug used for systemic fungal illness: amphotericin B

Question 4

amphotericin B

Answer 4

inhibits ergosterol synthesis in the cytoplasmic membrane of the fungal cell

Question 5

antiviral agents

Answer 5

• DNA/RNA synthesis inhibitors
• entry inhibitors
• uncoating inhibitor (M2 proton channel)
• nucleoside analogue
• protease inhibitors

Question 6

antiviral agent: azidothymidine AZT or zidovudine

Answer 6

inhibits the reverse transcriptase (synthesis of DNA from RNA) treats HIV

Question 7

bacteriostatic antibiotics

Answer 7

• stop the replication of bacteria
• do not kill the bacteria already present (erythromycin)

Question 8

bactericidal antibiotics

Answer 8

• kill the bacteria
• stop bacterial metabolism (penicillin)

Question 9

inhibition of cell wall synthesis

Answer 9

beta lactams:
- penicillins
- cephalosporins
- carbapenems
- monobactams
vancomycin bacitracin

Question 10

inhibition of protein synthesis

Answer 10

30s subunit
- tetracyclines
- aminoglycosides
50s subunit
- macrolides
- clindamycin
- linezolid
- chloramphenicol

Question 11

injury to the plasma membrane

Answer 11

polymyxins (topical)

Question 12

inhibit nucleic acid synthesis

Answer 12

DNA gyrase
- quinolones
RNA polymerase
- rifampin
folate synthesis
- sulfonamides
- trimethoprim

Question 13

inhibits the synthesis of essential metabolites

Question 14

specific antibiotics

Answer 14

• inhibit gram - or
• gram + or
• certain bacterial species

Question 15

broad spectrum antibiotics

Answer 15

• inhibits both gram - and gram + bacteria

Question 16

most susceptible to bacterial infection

Answer 16

• diabetics
• children
  -elderly
• burn wound: skin and soft tissue
• immunocompromised

Question 17

effects of antibiotics

Answer 17

• allergies (penicillin)
• pregnant women (tetracycline)
• children (pharmacokinetic and pharmacodynamic issues)
• people with liver of kidney damage

Question 18

antimicrobial side effects

Answer 18

• kidney
• liver
• rash, allergy
• GI upsets
• nerve damage
• ototoxicity
• teeth and bone formation in children
• cartilage formation in children

Question 19

antibiotic=not effective if used too late

Answer 19

• too many bacteria
• too much tissue damage
• formation of walled-off abscesses that can’t be penetrated by antibiotics
• poor absorption of drug

Question 20

why are IV antibiotics sometimes used

Answer 20

• GI problems
• only drug possible (vancomycin)
• rapid bioavailability

Question 21

clostridium perfringens

Answer 21

• gram + bacilli
• gangrene
• bacteremia and sepsis
• penicillin, clindamycin, metronidazole (anaerobic)

Question 22

pseudomonas aeruginosa

Answer 22

• gram -
• opportunistic pathogen
• inhabit soil and water
• needs very few nutrients
• can infect many body sites
• very common in burn patients and patients with cystic fibrosis
• has endotoxin, also produces exotoxins
• require broad spectrum drugs

Question 23

bacterial mutation to penicillin

Answer 23

• produced enzyme beta-lactamase or penicillinase: inactivation of penicillin by breaking the beta-lactam ring

Question 24

counteracting bacterial mutation to penicillin

Answer 24

• synthesis of semi-synthetic penicillins with a structure where the active portion of the antibiotics was protected from the enzymes

Question 25

4 ways bacteria become resistant to antibiotics

Answer 25

1. prevent penetration 2. destruction of drug 3. target site alteration 4. ejection of drug from bacterium

Question 26

r-factors

Answer 26

- plasmids that confer genes for resistance to antimicrobials - Genes coded on small circular independently replicating pieces of DNA called plasmids located in the cytoplasm of bacteria - Can be transferred from one bacteria to another by conjugation - R-factors can be transferred between different bacterial species

Question 27

why do bugs become resistant

Answer 27

- overuse - inappropriate treatment - incomplete treatment regimens

Question 28

what are superbugs

Answer 28

bacteria that can't be controlled by antibiotics

Question 29

what did the staphylococci do after semisynthetic drugs began to be used

Answer 29

- mutated again - MRSA: methicillin resistant s. aureus (superbug) - changes the penicillin binding site - penicillin binding protein 2 mutates to PBP2a

Question 30

superbug: VRE (vancomycin resistant enterococci)

Answer 30

- genetic mutations-several: in genes Van A, Van B, Van C - resistance developed after use of avoparcin in animal feed

Question 31

superbug: ESBL (extended spectrum beta-lactamase)

Answer 31

- Enterobacteriaceae like E. coli: genetic mutations, many resistance genes - Increasing problem in ICU, extended care - Resistance to penicillins and cephalosporins - ESBL can inactivate even the new really good beta-lactams like meropenem - NDM-1 (New Delhi metallobetalactamase is one of the latest enzyme variants)

Question 32

superbug: XDR-TB

Answer 32

- first seen in tugela ferry, south africa - resistant to both first and second line anti-TB drugs

Question 33

MIC (minimum inhibitory concentration)

Answer 33

- minimum amount of antimicrobial that will inhibit the growth of the microorganism - every important bacterial isolate must be tested - need to know for appropriate dosing levels and intervals

Question 34

what is a drug of choice

Answer 34

drug that is deemed to be the most effective with the least toxicity for a specific infection

Question 35

disk diffusion test

Answer 35

- for antimicrobial susceptibility - routine test, primarily for rapidly growing bacteria as the antibiotics on the disc will deteriorate with time 3 categories of sensitivity: S= sensitive or susceptible I= intermediate R= resistant

Question 36

kirby bauer or disk diffusion susceptibility test

Answer 36

- Interpretation: measure the zones of inhibition and compare to standard charts to get S,I,R - This is a one shot concentration of the antibiotic in each disc - You use this for infections like urinary tract infections, skin infections, but not for infections in sterile sites (like blood).

Question 37

e-test for MIC determination

Answer 37

- an easy way to determine MIC for a drug on a specific bacterial strain

Question 38

monitoring of serum antimicrobial levels

Answer 38

1. attain effective levels (over MIC) 2. prevent toxic side effects 3. ascertain dosing intervals

Question 39

MIC and SIR

Answer 39

personalize and control the dose