Infectious Disease Pt.3

Question 1

Why are antibiotics used for?

Answer 1

Prophylaxis – trying to prevent an infection –> in most cases, not appropriate and just drive resistance

Empiric therapy

Specific therapy

Question 2

When are antibiotics needed?

Answer 2

Obvious bacterial infections (pneumonia, wound infection, UTI, etc.) require antibiotics

Probable bacterial infections (patient with fever and symptoms, but no local findings) are more of a problem

Question 3

When you believe there is a probable infection, you should consider….

Answer 3

Consider age, other illnesses, travel history, etc.

Examine chance that symptoms could be due to other things

Consider likelihood of viral infection

Consider urgency of the situation

Ex. Possible acute endocarditis – may damage heart valves within days

Question 4

How can you determine which organisms are most likely?

Answer 4

Will depend upon the site of infection and circumstances leading up to it

Age of the patient may also provide clues (and may limit antibiotic selection)

Immunosuppressed patients may present with bacteria not seen in normal patients

Question 5

How to determine which drug is the best?

Answer 5

• Consider pt allergies? Are they real?
• Penetration issues –> Will it penetrate the CNS for tx of meningitis as example
• Location of the infection –> e.g. acidic pH of an abscess may alter activity
• S/e of antibiotic
• Bactericidal vs. bacteriostatic
• Consider cost and EDS status

Question 6

QTC Interval Prolongation is a concern when….

Answer 6

• an antibiotic capable of such s/e is used in a patient with CV effects
• In a normal pt, less of a concern

Question 7

Tetracycline’s and Fluroquinones are contraindicated in….

Answer 7

Kids
Pregnancy

Question 8

When choosing an antibiotic, one must consider….

Answer 8

• Frequency of admin
  Route of admin
  Monitoring of serum levels and toxicity

Narrow vs. Broad spectrum

Question 9

What is the difference between narrow vs. broad spectrum antibiotics?

Answer 9

• May use a broad spectrum as empiric therapy, but then tailor once culture and sensitivity has been done
• Want to choose the narrowest spectrum possible

Question 10

When is combination therapy appropriate?

Answer 10

• For most infections, one drug should suffice
• In diffiocult to tx diseases, use two things together to get a synergistic effect (e.g. TB)

Question 11

Define synergism

Answer 11

• When 1 antibiotic enhances the activity of another

Question 12

Synergistic Therapy for Enterococci

Answer 12

• E. faecalis

Penicillin and AMG
- Penicllin alters cell wall allowing the AMG to penetrate the bacteria

Question 13

Amoxicillin and Clavulanic Acid is an example of….

Answer 13

• Synergism
• Clavulanic acid inibits beta-lactamases allowing amoxicillin to enter the bacteria

Question 14

What are some disadvantages to using multiple antibiotics?

Answer 14

Increased risk of toxicities

Increased risk of colonization with resistant organisms

Higher costs

False sense of security

Question 15

Antibiotic use in pregnancy:

a) Safe
b) Caution
c) Avoid

Answer 15

Safe: Penicllins, cephalosporins, erthryomycin base

Caution: AMG, vancomycin, clindamycin, trimethoprim, nitrofurantoin

Avoid: tetracycline, fluroquinones, TMP-SMX, erthryomycin estolate, sulfonamides

Question 16

What are important pt (host) factors to consider?

Answer 16

Renal or hepatic function
-May affect not only the choice of antibiotic, but also it’s dose

Immunosuppressed
- Either from drugs, radiation or disease
- May need bactericidal antibiotics

Prosthetic devices

Ex. Infection of joint of knee replacement –> difficult to eradicate from device that do not have a blood supply –> Some drugs that penetrate biofilms better, etc.

Age
Some antibiotics should not be used in children
Higher mortality rates from infection is seen in elderly
Elderly may present differently with infection

Drug-drug interactions
Drug-disease interactions
Patient preference
Adherence

Question 17

In regards to serious infections, the route of admin is… Why?

Answer 17

• Parenteral
• ensures adequate blood levels
• are usually able to step down to oral therapy to complete the course of antibiotics

Question 18

How is a dose determined?

Answer 18

• Depends on the infection as well as patient factors

Question 19

What are some reasons for antibiotic failure?

Answer 19

Noncompliance
Under dosing
Inaccessible site (abscess)
Prosthetic material
Resistance
Superinfection –> a resistant organism –> often implies when a second infection results as a use of the first infection –> antibiotic driving the second infection
Some patients will not survive