L5 - Antibacterial chemotherapy Flashcards
Is food poisoning due to the virus or the toxin?
can be both
often toxin present WITHOUT virus
What is endogenous infection?
disease from commensal microbiota
What is exogenous infection?
disease from microbes that do not reside in the body e.g. TB
define antibiotics?
natural substances produced by one micro-organism that kill/inhibit another
define antibacterial agents?
compounds capable of killing/inhibiting bacteria - include semisynthetic/synthetic
define antibacterial drugs?
compounds that show selective toxicity against bacterial cells
define antibacterial chemotherapy?
use antibacterial drugs to treat bacterial infections
what are the recurring themes of antibacterial action?
substrate analogues
steric hindrance
enzyme inactivation
disruption/subversion
what is selective toxicity?
organism is killed without any damage to the host
What are the recurring themes for selective toxicity?
gets into bacterial cells more easily than mammalian
targets structures not present/different in mammalian cells
pro-drug only activated in bacteria
Names of 2 segments of antibiotic discovery?
Golden age - 1945-1970
Discovery void - 1990-2021
what % of antibacterial drug prescriptions are for oral use in primary care?
> 80-90%
What % of antibiotics prescribed are inappropriate?
50%
What is the process for uncomplicated infections?
choice of drug based on physical examination
empiric “best-guess” therapy
What is the process for complicated infections?
Hospitalised
refine drug choice based on lab diagnosis
susceptibility testing
What are 3 types of antibac susceptibility tests?
Disk diffusion assay
Etest - MIC
Broth/agar dilution
What is MIC?
minimum inhibitory concentration
What are factors that influence the choice of antibacterial drugs for therapeutic use?
Plasma concentration/half life
tissue distribution/concentration at site
dosing forms (oral/topical/IV)
potential adverse side effects
What are pharmacokinetics (PK)?
what the body does to the drug
What are pharmacodynamics (PD)?
What the drug does to the bacterium
What are pharmacokinetic considerations (CSF, urine)?
Cerebrospinal fluid:
B-lactams (good)
Aminoglycosides, vancomycin (bad)
Urine:
B-lactams, Trimethropin (good availability)
macrolides (bad)
Why is combination therapy good?
broad spectrum - single agent may not cover everything
boost activity via synergism
reduce resistance
What are adverse effects of antibiotics?
antibiotics resistance
endotoxin release (when lots of bacteria die at once = clinical deterioration - septic shock
superinfection e.g. C.diff
What happens in C.diff infection?
antibiotic-associated diarrhoea
gut flora ruined by antibiotics
