Antimicrobial Agents Intro

Question 1

What are the 3 classes of antimicrobial agents?

Answer 1

antibacterial
antivirals
antifungals

Question 2

T-F–life destroys life among the lower species?

Answer 2

True

Question 3

When was penicillin discovered? by who

Answer 3

1929, fleming

Question 4

When was sulfanilamide discovered?

Answer 4

1936

Question 5

The ideal antimicrobial agent acts selectively on what? What 4 ways is this achieved?

Answer 5

1. the pathogen and not the host

2. unique cell structure, unique biochem paths, altered component affinities, prodrug converted only by pathogen

Question 6

Review/memorize the 5 factors that determine cidal vs. static activity

Answer 6

1. drug’s mechanism
2. microbe’s state of growth
3. concentration of drug on organism
4. type of microbe
5. drug’s spectrum of activity

Question 7

What is the general rule of thumb for antibiotics in the blood?

Answer 7

should exceed the

MIC by 2-8X to offset tissue barriers to infection site

Question 8

What does narrow spectrum antibiotic mean?

Answer 8

mainly effective against G+ or G- microbes, lower risk for superinfections

Question 9

What does extended spectrum antibiotic mean?

Answer 9

affects a variety of G+ and G- bacteria

Question 10

What does broad spectrum antibiotic mean?

Answer 10

Affects both G+ and G-, and other organisms

Question 11

Are all the broad spectrum antibacterials bacteriostatic or bactericidal?

Answer 11

bacteriostatic

Question 12

What reflects the margin of
safety expected when using an antimicrobial agent
at its effective dose?

Answer 12

Chemotherapeutic index

TD50/ED50

Question 13

Does clinical effectiveness depend on maximal efficacy more or less than potency?

Answer 13

maximal efficacy

Question 14

Review the list of factors influencing efficacy

Answer 14

1. Host-immune function, pharmacokinetics, age, preg, genetics, allergy, eidemiologic exposure, compliance
2. Microbe-type and variability, body burden, growth rate, environment/site
3. drug drug interaction- synergy, antagonism, PK effects

Question 15

What are the 3 reasons for antimicrobial drug resistance?

Answer 15

1. Misdiagnosis
2. inherent microbial resistance
3. Acquired microbial resistance

Question 16

What are the 3 ways microbial resistance is acquired?

Answer 16

a. Drug fails to reach target
b. Drug is inactivated
c. Drug target is altered

Question 17

What are the common ways of genetic drug resistance? non-genetic?

Answer 17

1. chromosomal resistance, sex-plasmid and transposon mediated (transformation, transduction, conjugation)
2. growth latency, anaerobic conditions, protoplasts

Question 18

Review some epidemiology of resistance problems

Answer 18

2 million patients get infection in hospital–90,000 of them die
-70% of bacteria causing infections are drug resistant

Question 19

What are the 3 major drug resistant bacteria?

Answer 19

strep pneumoniae, MRSA, VRE

Question 20

What are 4 methods of avoiding drug resistance?

Answer 20

1. use only when needed
2. select the best antibiotic for the organism
3. use doses to establish effective concentrations for effective times
4. Use multiple drug therapy only when indicated

Question 21

When is combination antimicrobial therapy valid? 4

Answer 21

1. severe infection of unknown cause
2. polymicrobial infections
3. enhancement of antibacterial effects in treatment of specific infections
4. prevent emergence of resistant microorganisms

Question 22

What are the 3 potential results of combination antimicrobial therapy?

Answer 22

1. antagonism
2. addition
3. synergism

Question 23

What are the 2 main characteristics of antagonism between drugs?

Answer 23

a. Cidal plus static agents

b. Metabolizing enzyme induced

Question 24

What are the 3 main types of synergy in combination antimicrobial therapy?

Answer 24

a. Blockade of sequential steps in pathway
b. Inhibition of drug-inactivating enzyme
c. Enhancement of drug uptake

Question 25

What are the 3 main disadvantages of combination antimicrobial therapy?

Answer 25

1. Super-toxicity 2. Antagonism 3. Selection for drug-resistant bugs INCREASED COST TOO

Question 26

Prophylaxis represents 30-50% administered antibiotics in the US. When is prophylaxis commonly used?

Answer 26

1. pre-surgery in patients with indwelling medical devices 2. prevent wound infection following surgery 3. sexual contacts of patients with STDs

Question 27

Review the general considerations for appropriate antibiotic use?

Answer 27

1. General health of patient (immune function, severity of infection) 2. Where advisable, narrow spectrum agents preferred 3. Nosocomial infections – drug resistance 4. Cost 5. Cidal vs static 6. Dose alteration 7. Drug delivery • Oral, parenteral (IV, IM, insoluble salts), topical

Question 28

What are 4 adverse effects of antimicrobial therapy?

Answer 28

1. Allergy 2. super infection 3. organ toxicity 4. Selection of resistant microorganisms