Antibacterials Flashcards
What is an antibacterial drug?
Chemical substance that kills or inhibits the growth of bacteria at a discrete target site
Define antibiotic
Antibacterial drug of microbial origin
E.g. Penicillin from mold
What do antibiotics target?
DNA synthesis = quinolones, folic acid antagonists
Protein synthesis = aminoglycosides, macrolides, tetracyclines
Cell wall synthesis = beta-lactams, glycopeptides
When should antibacterials be used?
Prevention of infections = undergoing surgery, meningitis contacts, asplenia, immunodef
Therapy of significant bacterial infection
What is a clinically significant bacterial infection?
Mean an infection that if left untreated will cause death, permanent harm or medium to long term disability
What factors need to be considered when asking what is the likely cause of infection?
Duration of illness
PMH
Occupational history
Travel history
Time of year
Age
Personal background
Anatomical site
What factors need to be considered when asking what ABX are likely to be effective?
Community or healthcare
Severity of infection
Immune status of pt
Baseline rate of resistance
What ADRs are associated with ABX
Toxicities
Allergic reactions
Idiosyncratic reaction
Ecological effects – C.diff, selection of resistance
Drug interactions
How can we measure the susceptibility of bacteria to antibacterials?
Disk sensitivity testing = diff ABX on an agar plant inoculated with the bacteria, examine zone of inhibition
MIC = minimum concentration of the ABX required to kill the bacteria
Outline the pharmacokinetics of ABX
Administration = oral, IV
Many ABX are only available IV
Physio-anatomical barrier = BBB, blood-retina barrier, prostate, bone
Body size and composition can influence PK
Why is therapeutic drug monitoring used?
Ensure adequate dose
Ensure non-toxic dose
Outline the pharmacodynamics of ABX
Time dependent killing = prolonged ABX presence at site of infection, but not high conc
Conc dependent killing = high ABX conc at site of infection, but not long time
Outline the genetic basis of ABX resistance
Chromosomal gene mutation
Horizontal
What are the methods of ABX resistance?
Antibiotic inactivation
Alteration of target site
Alteration of metabolic pathways
Reduced intracellular ABX accumulation – efflux pumps
Concerning antimicrobial stewardship, what are the intervention types?
1) persuasive = education, opinion leaders, reminders, audits
2) restrictive = formulary restriction, prior authorisation, automatic stop orders
3) structural = computerised records, rapid lab tests, quality monitoring
