Abx Selection

Question 1

Primary Prophylaxis Def

Answer 1

Prevention of first infection in susceptible populations (e.g., surgical, HIV opportunistic infection, etc.)

Question 2

Secondary Prophylaxis def

Answer 2

Prevention of subsequent infection (e.g., recurrent UTI, HIV opportunistic infection, spontaneous bacterial peritonitis, etc.)

Question 3

Empiric therapy def

Answer 3

Treatable infection is suspected but unproven; treatment is based on most likely organism(s) and susceptibilities

Question 4

Targeted therapy

• aka (2)
• def

Answer 4

• Definitive and specific therapy

- Treatment of proven infection usually with organism identification and antibiotic susceptibilities available

Question 5

Concentration-dependent bacterial killing def

Answer 5

Rate and extent of bacterial killing increases with increasing antibiotic concentration above the minimum inhibitory concentration (MIC)

Question 6

Two examples of concentration dependent bacterial abx

Answer 6

aminoglycosides and fluoroquinolones

Question 7

How are concentration dependent bacteria typically dosed

Answer 7

Are usually used in high-dose intermittent therapy regimens and they are usually dosed less frequently

Question 8

Concentration-independent bacterial killing

• aka
• def

Answer 8

• aka time dependent

- Extent of bacterial killing dependent on time of drug exposure

Question 9

Two examples of concentration-independent bacterial killing

Answer 9

beta-lactams and vancomycin

Question 10

concentration-independent bacterial killing typical dosing

Answer 10

Are usually used in multiple daily doses or in extended or continuous infusions, usually with lower doses

Question 11

Antibiotic therapy de-escalation def

Answer 11

After starting broad-spectrum empiric therapy in order to avoid inadequate initial therapy, the spectrum of the antimicrobial regimen is narrowed based on clinical improvement, culture and susceptibility results, and/or laboratory results

Question 12

When is antibiotic therapy intensification used

Answer 12

When there is a treatment failure or a non-response

Question 13

Three types of antibiotic therapy intensification

Answer 13

1. Broaden antimicrobial spectrum by adding another antibiotic to the current agent or selecting a new one with a broader spectrum
2. Add or switch to an antibiotic with a different mechanism of action
3. Re-evaluate potential causes for treatment failure

Question 14

Specific questions that should be asked when gathering the history from a patient with a suspected infection

Answer 14

All part of the patient interview:

1. Sick contacts (e.g. children in daycare, tuberculosis case contact)
2. Unusual pets Bird, reptiles carry odd diseases
3. Exposures (e.g., occupational, recreational, etc.)
4. Recent travel (endemic infectious pathogens, developing countries)
5. Medications – any that cause immunosuppression

Question 15

5 common antibiotic classes usually requiring dosing adjustments based on renal function

Answer 15

1. Beta-lactams
2. Fluoroquinolones
3. Aminoglycosides
4. Vancomycin – always, can cause nephrotoxicity
5. Trimethoprim-sulfamethoxazole (TMP/SMX)

Question 16

Types of infections requiring bactericidal antibiotic therapy (4)

Answer 16

• endocarditis
• meningitis
• osteomyelitis
• immunocompromised patients (neutropenia due to cancer chemotherapy and other causes)

Question 17

Situations usually adequately treated by bacteriostatic antibiotic therapy

Answer 17

Adequate for many infections in immunocompetent patients

May be more appropriate for organisms that release toxins as a result of bacterial lysis

Question 18

Types of infections usually managed with home intravenous therapy

Answer 18

Stable infections requiring prolonged IV treatment:

• osteomyelitis
• prosthetic joint infections
• endocarditis

Question 19

ID 2 abx combinations demonstrating antimicrobial synergy

Answer 19

• Enterococcal endocarditis treated by penicillin + aminoglycoside
• Trimethoprim + sulfamethoxazole (TMP/SMX) Bactrim as a product is a synergistic product

Question 20

Two kinds of infections often managed with combination antibiotic therapy to prevent development of resistance

Answer 20

1. Tuberculosis - different abx combos depending on global location of exposure
2. Helicobacter pylori infections

Question 21

4 Potential disadvantages of combination antibiotic therapy

Answer 21

1. Additive drug toxicity (e.g., vancomycin enhances nephrotoxicity of aminoglycosides)
2. Increased risk of colonization with resistant organisms – “collateral damage”
3. Drug inactivation/ antagonism (antimicrobial action of combination is less than that of either agent alone) ex: penicillin and tetracycline
4. Increased cost

Question 22

ID 3 potential causes of antimicrobial failure

Answer 22

1. drug selection
2. host factors
3. Microorganism factors

Question 23

Drug selection as a cause of abx failure (5)

Answer 23

1. Inappropriate spectrum of activity
2. Inappropriate route of administration (e.g., malabsorption)
3. Subtherapeutic dosing
4. Drug interactions
5. Poor penetration into site of infection

Question 24

Host factor as a cause of abx failure (2)

Answer 24

1. Immunosuppression results in inadequate host defenses to augment antimicrobial effects
2. Need for surgical intervention (e.g., abscess drainage)

Question 25

Microorganism as a cause of abx failure (1)

Answer 25

resistant to selected antibiotic(s)

Question 26

6 abx with good oral bioavailability

Answer 26

1. fluoroquinolones
2. clindamycin
3. doxycycline
4. linezolid
5. metronidazole
6. TMP/SMX (bactrim)