Microbio - Antimicrobials 2 Flashcards
What are reasons for antibiotic misuse
No infection present
Selection of incorrect drug
Inadequate or excessive dose
Inappropriate drug therapy (lack of evidence for optimum therapy time)
Expensive agent used when cheaper is available
What proportion of people using antimicrobials experience adverse events and what are the most common
5%
GI upset
Fever and rash
Renal dysfunction
Acute anaphylaxis
Hepatitis
What are the CHAOS of things to consider when prescribing antimicrobials
C Choice of correct antimicrobial depends upon the…
H Host characteristics (i.e. renal failure, pregnancy, allergy, age, genetics, hepatic function)
A Antimicrobial susceptibilities of the…
O Organism itself and also the…
S Site of infection (i.e. bone, CSF, urine)
What are the ideal features of antibiotics when considering choice
Narrow spectrum
Bactericidal
Based on bacteriological diagnosis
Considers local sensitivity patterns
Considers patient characteristics
Cheap cost
What pharmacological factors should be considered when choosing a drug
Pharmacokinetics (absorption, distribution, elimination)
Route of administration
Dosage (age, renal/hepatic function, drug monitoring)
What consideration for antibiotics administration should be made in those who are septic
May have hypotension → perfusion of the intestines will be low → oral drug absorption may be compromised
When are IV antibiotics indicated
The infection is serious
Patient is not absorbing orally
There is a deep infection
Treat CNS infection
What is the minimum inhibitory concentration
This is the minimum drug concentration that is required to inhibit the growth of the organism in a culture
What is the break point for MICs
Break point = A “line”, whereby if the MIC falls above this line (i.e. higher concentration required for inhibition), then the antibiotic is unlikely to be useful at the usual doses
→ reported as resistant
What is the Agar Disc Diffusion Method (EUCAST)
The disc is impregnated with antibiotic which diffuses out from the disc into the agar medium
As distance from disc increases, concentration of the antibiotic decreases logarithmically
The border of the clear zone is the MIC
In what conditions are broad spectrum empirical antibiotics indiacted
Serious or deep-seated infection
Nosocomial pneumonia
Severe sepsis/septic shock
What are the methods for identifying organisms
Gram-staining (send as much specimen as possible → higher volume of sample means higher sensitivity)
- CSF
- Joint aspirate
- Pus
Rapid antigen detection
Immunofluorescence
PCR
Why does the site of infection impact decisions for antibiotics
Local concentration of the antimicrobial will be affected by factors such as:
* pH at the infection site
* Lipid-solubility of the drug
* Ability to penetrate the blood-brain barrier
Special considerations are needed for endocarditis and osteomyelitis
Why would oral administration of Abx be considered over other routes
Easier, can be taken at home
IV to PO switch recommended if the patient is stabilised (But NOT in osteomyelitis and endocarditis)
When would IM Abx NOT be useful
Long-term requirement
Bleeding tendency
Locally irritant
