Principles of Antimicrobial Use Flashcards
What does “antimicrobial stewardship” means?
Careful & responsible management of antimicrobials through the use of a systematic approach.
List the steps of the systematic approach to antimicrobial use.
1) Indications for Abx
(a) Confirm presence of infection
(b) Identification of pathogens
2) Regimen (choice, ROA, dose, duration)
(a) Selection of antimicrobial & regimen
3) Monitoring & Plan
(a) Monitor response
What are some host factors that increase the risk of infection in an individual?
1) Disruption of natural protective barriers (innate immunity)
2) Age
- Young children -> Immature immune system
- Elderly -> Impaired & aged immune system
3) Immunosuppression
- Malnutrition
- Underlying diseases
- Drugs (i.e. immunosuppressants, chemotherapy, steroids)
4) Alterations to normal host flora
What are some localised subjective symptoms observed in patients with ongoing infections?
1) GI disturbances (N/V/D, abdominal distension)
2) Respiratory symptoms (cough, purulent sputum)
3) Urinary disturbances (dysuria, frequency, urgency)
4) Pain & inflammation at site of infection (erythema, swelling, warmth)
5) Purulent discharge (wound, vaginal, urethral)
What are some systemic subjective symptoms observed in patients with ongoing infections?
1) Fever, chills & rigours
2) Malaise / general tiredness
3) Palpitations
4) Shortness of breath
5) Mental status changes
6) Weakness
List some objective parameters used to help with the confirmation of a likely infection in an individual.
1) Vital signs
2) Laboratory test
3) Radiological imaging
What are some vital signs observed in an individual who is likely undergoing an infection?
1) Fever (Temperature > 38 degrees Celsius)
2) Hypotension (SBP < 100 mmHg)
3) Tachypnea (RR > 22 bpm)
4) Tachycardia (HR > 90 bpm)
5) Mental status (esp. in elderly) via drop in Glasgow coma scale
A patient is currently experiencing a fever of temperature above 38 degrees Celsius and does not display any other symptoms currently. Is there sufficient evidence to indicate Abx for this patient? Why so?
No! While fever is a hallmark of infection, there is a need to exclude other non-infectious causes of fever first.
Non-infectious causes of fever can include:
- Cancer
- Intracranial haemorrhage
- Drug fever (i.e. beta-lactams, antiepileptics, anti-convulsants & allopurinol)
- Hyperthyroidism & thyroid medications
Do inflammatory laboratory markers suffice as infection laboratory markers?
No
List the laboratory biomarkers used to indicate an infection in an individual.
1) Non-specific biomarkers
- Elevated or depressed total WBC (TW > 10 x 10^9 /L or TW < 4 x 10^9 /L)
- Increased neutrophils (% > 75%)
- Increased C-reactive protein (CRP) (infection > 40 mg/L)
2) Specific biomarkers
- Increased erythrocyte sedimentation rate (ESR)
- Increased procalcitonin (start Abx when > 0.5mcg/L)
At what concentration of procalcitonin should the use of antibiotics be encouraged in patients with ongoing infections?
> = 0.5 mcg/L
What are the conditions in which antibiotics should be discontinued in patients who had infections?
1) [procalcitonin] < 0.5 mcg/L
OR
2) Decrease by 80% from peak concentration
For a patient whose [procalcitonin] = 0.6 mcg/L, and shown to have decreased by < 80% from peak concentration, should the use of Abx be discontinued?
No. Continuation of Abx is encouraged when [procalcitonin] >= 0.5 mcg/L AND decrease in peak concentration < 80%.
Under what conditions should a change in Abx be considered in a patient suffering from an infection?
1) Increased [procalcitonin] compared to peak concentration
AND
2) [procalcitonin] >= 0.5 mcg/L
For a patient with chronic kidney disease who display signs of an infection, what should be considered when determining the need to initiate antibiotics?
Important to consider the trend of [procalcitonin], rather than absolute values.
- Compare pt. baseline [procalcitonin] against current values instead due to already elevated procalcitonin levels in CKD pt.
What should we look for when using radiological imaging to determine if a patient is currently infected?
Tissue changes, collections, abscesses & obstructions.
Why is it extremely important to obtain cultures before administering antimicrobials?
- Follow-up cultures are much less reliable than pre-treatment cultures.
- Empiric Tx may have been initiated & key pathogens may have been targeted already upon taking follow-up cultures.
- Inability to narrow down / de-escalate Abx Tx
- Development of Abx resistance
Differentiate between pathogens, colonisers & contaminants.
1) Pathogens: Capable of damaging host tissues & elicit host response, producing signs & symptoms of infection
2) Colonisers: Presence of normal flora & pathogenic organisms w/o eliciting host response
3) Contaminants: Typically acquired during collections/processing of host specimens w/o eliciting host response
Name a likely contaminant from blood culture.
1) Staphylococcus epidermidis
2) Bacillus spp.
Name a likely coloniser from urine culture.
Yeast
Explain the differences between empiric, definitive & prophylaxis antimicrobial therapy.
Empiric:
- Microbiological results are NOT available
- Abx use based on clinical presentation on likely site of infection, likely organism causing infection & likely susceptibility from antibiogram
Definitive/Culture-Directed:
- Abx use based on patient-specific microbiological (i.e. culture & susceptibility) results
Prophylaxis:
- Infection prevention
- E.g. surgical prophylaxis & post-exposure prophylaxis (STD, HIV)
What are the principles of antimicrobial use to achieve improved patient outcomes?
1) Timely initiation of appropriate agents (i.e. most effective, least toxic & narrowest-spectrum)
- Active antimicrobials should be administered ASAP esp. in severely ill pt.
2) Dosage individualised administration
3) Use Abx for shortest duration possible
What are the factors affecting the selection of antimicrobial agents to treat infections?
1) Host (patient) factors
2) Organism factors
3) Drug factors
Discuss the organism factors affecting the selection of antimicrobial agents.
1) Identity of infecting organism
- fungus, bacterium or virus?
- genus and species?
2) Susceptibility & resistance of infecting organisms
- Empiric: consider antibiogram
- Definitive: select active Abx according to AST
- Risk factor for multi-drug resistance
3) Consider combination therapy if required
