Infectious Disease Pt.3 Flashcards
Why are antibiotics used for?
Prophylaxis – trying to prevent an infection –> in most cases, not appropriate and just drive resistance
Empiric therapy
Specific therapy
When are antibiotics needed?
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
When you believe there is a probable infection, you should consider….
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
How can you determine which organisms are most likely?
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
How to determine which drug is the best?
- 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
QTC Interval Prolongation is a concern when….
- an antibiotic capable of such s/e is used in a patient with CV effects
- In a normal pt, less of a concern
Tetracycline’s and Fluroquinones are contraindicated in….
Kids
Pregnancy
When choosing an antibiotic, one must consider….
- Frequency of admin
Route of admin
Monitoring of serum levels and toxicity
Narrow vs. Broad spectrum
What is the difference between narrow vs. broad spectrum antibiotics?
- 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
When is combination therapy appropriate?
- For most infections, one drug should suffice
- In diffiocult to tx diseases, use two things together to get a synergistic effect (e.g. TB)
Define synergism
- When 1 antibiotic enhances the activity of another
Synergistic Therapy for Enterococci
- E. faecalis
Penicillin and AMG
- Penicllin alters cell wall allowing the AMG to penetrate the bacteria
Amoxicillin and Clavulanic Acid is an example of….
- Synergism
- Clavulanic acid inibits beta-lactamases allowing amoxicillin to enter the bacteria
What are some disadvantages to using multiple antibiotics?
Increased risk of toxicities
Increased risk of colonization with resistant organisms
Higher costs
False sense of security
Antibiotic use in pregnancy:
a) Safe
b) Caution
c) Avoid
Safe: Penicllins, cephalosporins, erthryomycin base
Caution: AMG, vancomycin, clindamycin, trimethoprim, nitrofurantoin
Avoid: tetracycline, fluroquinones, TMP-SMX, erthryomycin estolate, sulfonamides
What are important pt (host) factors to consider?
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
In regards to serious infections, the route of admin is… Why?
- Parenteral
- ensures adequate blood levels
- are usually able to step down to oral therapy to complete the course of antibiotics
How is a dose determined?
- Depends on the infection as well as patient factors
What are some reasons for antibiotic failure?
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
