Antibiotic Factors

Question 1

Empiric Therapy

Answer 1

broad spectrum antibiotics before pathogen identification

Question 2

Critically ill patients

Answer 2

antibiotic therapy initiated immediately or concurrently with collection of diagnostic specimens

Question 3

Bacterial endocarditis and osteomyelitis

Answer 3

may hold antibiotic therapy until appropriate testing done

Question 4

Directed therapy

Answer 4

de-escalated to agent with narrowest effective spectrum of activity, after identification of pathogen is known

Question 5

Considerations for empiric therapy

Answer 5

• knowledge of likely pathogens to cause specific infections
• anticipated antimicrobial susceptibility
• information from patient history and physical exam

Question 6

Bactericidal (these effects can be specific to different organisms)

Answer 6

= organisms are killed by acting on the cell wall, cell membranes, or DNA

Question 7

Bacteriostatic (these effects can be specific to different organisms)

Answer 7

inhibit bacterial replication without

killing the organism by inhibiting protein synthesis

Question 8

Reasons for combination therapy

Answer 8

• broaden spectrum coverage for empiric therapy
• achieve synergistic bactericidal activity against a pathogen
• prevent emergence of resistance

Question 9

Disadvantages of combination therapy

Answer 9

• increased cost
• greater risk of toxicity
• super infection with resistant bacteria
• antagonism

Question 10

Selecting antimicrobial therapy efficacy

Answer 10

clinical and bacteriologic effect
FDA-approved vs. non-approved indications
many problems with newer agents since patients are usually excluded, (small sample sizes)

Question 11

Selecting antimicrobial therapy in vitro microbiologic activity

Answer 11

spectrum of activity, susceptibility tests, resistance trends and mechanisms

Question 12

selecting antimicrobial therapy pk

Answer 12

• absorption -> may be impaired by disease state, surgery, drug therapy
• distribution -> achievable in bloodstream, and sites of infection
• metabolic
• elimination -> not the same as metabolism
• tissue distribution (assessed via micro dialysis)

Question 13

selecting antimicrobial therapy pd

Answer 13

• study of biochemical and physiological effects of drugs and their MOA.
• in-vitro concentration dependent activity
• in-vivo effects time above MIC

Question 14

selecting antimicrobial therapy adverse effects

Answer 14

• risk/benefit analysis

problems with new agents are small sample sizes

Question 15

selecting antimicrobial therapy drug-drug and drug food interactions

Answer 15

• isoenzymes that effect CYP450 (rifampin, voriconazole
• complexation/chelation (Fluoroquinolones and divalent/trivalent cations), tetracyclines, acronym ZICAM, enteral nutriotion products

Question 16

Criteria for selection antimicrobial therapy

Answer 16

misuse
- prolonged empiric use without evidence of infection
- treatment of a positive culture in absense of infection
- failure to narrow empiric therapy when pathogen is identified
- prolonged prophylactic therapy
Excessive use of certain agents

Question 17

Criteria for switch to oral therapy

Answer 17

overall clinical improvement
lack of fever for 24 hours
decreasing WBC count
Functioning GI Tract
Acceptable agent with good availability

Question 18

Assessment of clinical failures

Answer 18

• reevaluate therapy after 2-3 days
• check for incorrect dx, incorrect antibiotic selection, and host factors
• incorrect organism
• laboratory errors