Principles of antimicrobial use Flashcards
What is an infection?
organism/pathogen invades host tissues and elicit inflammatory/immune host responses
What is sepsis?
life-threatening organ dysfn caused by dysregulated host response to infection
What are the 4 things in a systemic approach to antimicrobial use?
- Confirm presence of infection
- Identify likely pathogens
- Select antimicrobial agents and regimen
- Monitor response
Which 2 steps fall under indication for Abx?
- Confirm presence of infection
2. Identification of (likely) pathogens
Which step falls under the ‘regimen (choice, route, dose, duration)’
Step 3: Selection of antimicrobial and regimen
Which step falls under the ‘monitoring and plan’?
Step 4: Monitor response
How to confirm presence of infection?
a. Any risk factors for infection
b. subjective evidence
c. objective evidence
d. Possible site of infection
- looking for diagnosis
What are 4 risk factors to look at for infection?
- Disruption of natural protective barriers (innate immunity)
- Age
- Immunosuppression
- Alterations in normal flora of the host with conditions that promotes overgrowth of MO
What to look at for subjective evidence?
- Localised symptoms (diarrhoea, N/V, dysuria, pain, purulent discharge)
- Systemic symptoms (feverish, SOB, weakness/tiredness, etc.)
What to look at for objective evidence?
- Vital signs (Fever, Hypotension, Tachypnoea, HR, Mental status)
- Lab test (non-specific biomarkers, acute-phase reactants)
- Radiological imaging
CONSIDER TREND; baseline VS current values
Guidelines for starting of ABx: When procalcitonin levels are?
> = 0.5 ug/L: ABx encouraged
Guidelines for continuing of ABx: When procalcitonin levels are?
decrease by 80% from peak concentration; and >= 0.5 ug/L: Continue Abx
Guidelines for stopping of ABx: When procalcitonin levels are?
< 0.5 ug/L: Stop Abx
How do we find the possible site of infection?
- Clinical presentation
- Risk of infections
- O and S evidence
- Common sites are UTI, Resp tract, soft tissues, intra-abdominal
What is considered a pathogen?
Organisms capable of damaging host tissue and eliciting a host response and signs and sx of an infection
What is a coloniser? Example?
Presence of normal flora/pathogenic organisms without eliciting a host response
e.g. yeast from urine culture
What is a contaminant?
Example?
Presence of MO typically acquired during collection/processing of host specimens w/o evidence of host response
e.g. S. epidermidis (from skin) + bacillus spp.
What is empiric therapy? and when to use empiric therapy?
- When micrological results are unavailable
- Clinical presentation of likely site of infection
- Likely susceptibility
- Antibiogram
What is definitive therapy? and when to use definitive therapy?
- Culture-directed therapy
- based on pts specific microbiological (culture and susceptibility tests)
What is prophylaxis therapy? and when to use prophylaxis therapy?
- Abx given to prevent infection
e. g. surgical prophylaxis; post-exposure prophylaxis
Benefits of combination therapy?
- Extend spectrum of activity
e. g. pip-tazo + vancomycin (covers MRSA) for HA-pneumonia
e. g. pip-tazo + ciprofloxacin (to broaden; cover p.aeruginosa) for VA-pneumonia - Achieve synergistic bactericidal effect (however, note that indifference/antagonism happens too)
e. g ampicillin + gentamicin or amipicllin + ceftriaxone for enterococcus endocarditis - Prevent development of resistance
e. g. TB treatment
Limitations of combination therapy?
- Inc toxicity and allergic rxns
- Inc risk of DDI
- Inc cost
- Selection of MDR bacteria
- Inc risk of superinfections
- Concern for antagonistic effect (VS synergisitc)
What are some host factors to consider when choosing the ABx?
- Age
- G6PD def
- History of allergies and ADR
- Cross-reactivity btw penicillins and other b-lactams
- Preg/lactation
- Renal/hepatic impairment
- Status of host immune fn (use bactericidal drugs for immunocompromised + combination therapy as more vulnerable to polymicrobial infection)
- Severity of illness
(may need broader spectrum e.g. covering Pseudomonas) - Recent Abx use
What are some drug properties to consider when choosing the ABx?
- Active against suspected organism
- Ability to reach site of infection (CNS penetration)
- PK-PD
- ROA
- Side effects
- DDI
- Cost