Abx Selection Flashcards
Primary Prophylaxis Def
Prevention of first infection in susceptible populations (e.g., surgical, HIV opportunistic infection, etc.)
Secondary Prophylaxis def
Prevention of subsequent infection (e.g., recurrent UTI, HIV opportunistic infection, spontaneous bacterial peritonitis, etc.)
Empiric therapy def
Treatable infection is suspected but unproven; treatment is based on most likely organism(s) and susceptibilities
Targeted therapy
- aka (2)
- def
- Definitive and specific therapy
- Treatment of proven infection usually with organism identification and antibiotic susceptibilities available
Concentration-dependent bacterial killing def
Rate and extent of bacterial killing increases with increasing antibiotic concentration above the minimum inhibitory concentration (MIC)
Two examples of concentration dependent bacterial abx
aminoglycosides and fluoroquinolones
How are concentration dependent bacteria typically dosed
Are usually used in high-dose intermittent therapy regimens and they are usually dosed less frequently
Concentration-independent bacterial killing
- aka
- def
- aka time dependent
- Extent of bacterial killing dependent on time of drug exposure
Two examples of concentration-independent bacterial killing
beta-lactams and vancomycin
concentration-independent bacterial killing typical dosing
Are usually used in multiple daily doses or in extended or continuous infusions, usually with lower doses
Antibiotic therapy de-escalation def
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
When is antibiotic therapy intensification used
When there is a treatment failure or a non-response
Three types of antibiotic therapy intensification
- Broaden antimicrobial spectrum by adding another antibiotic to the current agent or selecting a new one with a broader spectrum
- Add or switch to an antibiotic with a different mechanism of action
- Re-evaluate potential causes for treatment failure
Specific questions that should be asked when gathering the history from a patient with a suspected infection
All part of the patient interview:
- Sick contacts (e.g. children in daycare, tuberculosis case contact)
- Unusual pets Bird, reptiles carry odd diseases
- Exposures (e.g., occupational, recreational, etc.)
- Recent travel (endemic infectious pathogens, developing countries)
- Medications – any that cause immunosuppression
5 common antibiotic classes usually requiring dosing adjustments based on renal function
- Beta-lactams
- Fluoroquinolones
- Aminoglycosides
- Vancomycin – always, can cause nephrotoxicity
- Trimethoprim-sulfamethoxazole (TMP/SMX)
Types of infections requiring bactericidal antibiotic therapy (4)
- endocarditis
- meningitis
- osteomyelitis
- immunocompromised patients (neutropenia due to cancer chemotherapy and other causes)
Situations usually adequately treated by bacteriostatic antibiotic therapy
Adequate for many infections in immunocompetent patients
May be more appropriate for organisms that release toxins as a result of bacterial lysis
Types of infections usually managed with home intravenous therapy
Stable infections requiring prolonged IV treatment:
- osteomyelitis
- prosthetic joint infections
- endocarditis
ID 2 abx combinations demonstrating antimicrobial synergy
- Enterococcal endocarditis treated by penicillin + aminoglycoside
- Trimethoprim + sulfamethoxazole (TMP/SMX) Bactrim as a product is a synergistic product
Two kinds of infections often managed with combination antibiotic therapy to prevent development of resistance
- Tuberculosis - different abx combos depending on global location of exposure
- Helicobacter pylori infections
4 Potential disadvantages of combination antibiotic therapy
- Additive drug toxicity (e.g., vancomycin enhances nephrotoxicity of aminoglycosides)
- Increased risk of colonization with resistant organisms – “collateral damage”
- Drug inactivation/ antagonism (antimicrobial action of combination is less than that of either agent alone) ex: penicillin and tetracycline
- Increased cost
ID 3 potential causes of antimicrobial failure
- drug selection
- host factors
- Microorganism factors
Drug selection as a cause of abx failure (5)
- Inappropriate spectrum of activity
- Inappropriate route of administration (e.g., malabsorption)
- Subtherapeutic dosing
- Drug interactions
- Poor penetration into site of infection
Host factor as a cause of abx failure (2)
- Immunosuppression results in inadequate host defenses to augment antimicrobial effects
- Need for surgical intervention (e.g., abscess drainage)
Microorganism as a cause of abx failure (1)
resistant to selected antibiotic(s)
6 abx with good oral bioavailability
- fluoroquinolones
- clindamycin
- doxycycline
- linezolid
- metronidazole
- TMP/SMX (bactrim)