Principles of Antimicrobial Therapy Flashcards
What are the 3 important factors of antimicrobials?
Host, Bacterial Pathogen, Antimicrobial drugs
Goals of antimicrobial treatment
To kill bacteria, avoid resistance and avoid toxicity
Categories of antimicrobial therapy
- Prophylaxis (prevention)- no infection
- Pre-emptive (preventing spread)- infection
- Empiric* (resistance builds)- symptoms
- Definitive- pathogen isolation
- Suppressive- Resolution
Empiric selection
Without IDing the causative organisms and patterns
Serious disease (life-threatening)
When shouldn’t antimicrobials be used?
Fever or leukocytosis alone
Cats with lower UT symptoms
Diarrheas in dogs and cats
Pancreatitis
What helps with IDing microbes and drugs?
The source of infection
Genitourinary tract infections
Gram - aerobes
Abdominal infections
Initially gram - aerobes followed by anaerobes
Skin infections
Staph. spps (gram +)
Abscess infections
Anaerobes and Pasteurella spp.
UTIs
E. coli (60-65%)
Proteus mirabillis (15-20%)
T/F: You shouldn’t need to treat Kennel cough with antimicrobials
TRUE
Most uncomplicated cases are self-limiting
1st tier (1st line) antimicrobial drugs
Clear diagnosis
No risk factors for resistance
2nd tier (2nd line) antimicrobial drugs
Antimicrobial susceptibility tests are mandatory if needed
3rd tier (3rd line) antimicrobial drugs
Reserved for highly resistant infections
Strongly discouraged
If necessary, use in consult with specialists
Considerations when using antimicrobial drugs
Reserved drugs
Multidrug resistance, ESBL
Safety
Convenience
Bactericidal concentration required in case of…
- Existing immunosuppression/ neutropenia
- Life-threatening/ serious infections
Drug concentration in tissue depends on …
Concentration in blood
Protein binding in plasma
Lipid solubility
Ionic charge (pH)
Binding to exudate or tissue
Presence of inflammation
Excretion pathway
Bacteriostatic drugs
Need to maximize the serum peak concentration to ↑ efficacy and reduced resistance
Peak concentration several fold MIC
Drug toxicity to the host
Hypersensitivity
Direct toxicity
Inhibition of normal microflora
Immunosuppression
Drug interactions
Therapeutic index (TI)
Dose toxic to host : effective therapeutic dose
Consider _______________ in food animals
Withdrawal time
Resistance avoidance
Use only if necessary
Perform susceptibility tests when applicable
ID optimal duration for treatment
Envision drug combos
Favor synthetic drugs when possible
MIC (minimum inhibitory concentration)
Lowest concentration of the antibiotic that results in inhibition of visible growth
Below MIC = no effect
MBC (minimum bactericidal concentration)
Lowest concentration of the antibiotic that kills 99.9% of the original inoculum in a given time (lab)
If the MBC/MIC is over 4 then the antibiotic is _______
Bacteriostatic
If the MBC/MIC is = to or less than 4 then the antibiotic is _______
Bacteriocidal
MPC (mutant prevention concentration)
High dose gets rid of all bacteria- severe infections (measured in serum)
Post antibiotic effect
Persistent suppression of bacterial growth after short exposure to the abx
Exhibited by conc. dependent drugs
Concentration (dose dependent drugs)
Cmax : MIC = dose 10-12 x more than MIC (can be over, never under)
Time-dependent drugs
T> MIC 50-100%
Transfer of bacterial resistance
Horizontal gene transfer
Vertical gene transfer
Gene amplification
Mutation
Horizontal gene transfer
Most common
Conjugation, transduction and transformation
Vertical gene transfer
Parent to offspring during bacterial reproduction
Gene amplification
Resistance gene is present in multiple copies within the bacterium, ↑ its expression and leading to ↑ resistance
Mutation
Mutation in a gene that codes for a target protein of abx
