Antibiotics Flashcards
What is an antibiotic?
Chemicals produced by microorganisms or plants that inhibit the growth of, and/or kill bacteria
What is an antimicrobial?
An all encompassing term for all compounds which are active against one type of microbe, including:
- antivirals
- antibiotics
- antifungals
- antimalarials
What reasons can antibiotics be used for?
- treatment of bacterial infection
- prophylaxis to prevent bacterial infection (e.g pre/post surgery, contacts in outbreaks)
What are the targets from antibacterial action?
- cell wall synthesis inhibitors
- cell membrane
- nucleic acid synthesis
- protein synthesis
Are antibiotics specific for bacteria?
Not all
Some may share targets present in other eukaryotes and therefore we try to find antibacterial with selective toxicity
What is selective toxicity?
Ability of a drug to target sites relative to a specific organism and not cause side effects in the host
What are the classes of antibiotics in clinical use?
- Beta lactams
- glycopeptides
- aminoglycosides
- tetracyclines
- chloramphenicol
- macrolides
How do you decide which antibiotic to use?
Effectiveness is an interplay between patient, infecting organism and drug:
– Clinical evaluation : • Typical pathogen for that site • Agents proven to be effective for that infection – Laboratory evaluation: • Isolation of pathogen • Susceptibility of pathogen
How do we determine susceptibility of an antibiotic?
Disc susceptibility
E-test
What is the MIC?
- minimum inhibitory conc
- dilution of a drug that inhibits growth
What factors limit antimicrobial efficacy?
- speed of action
- sensitivity of target
- adverse events
What is the breakpoint concentration?
the concentration below which bacteria are classes as susceptible
What are the three different outcomes for treating an illness with multiple antibiotics?
- synergy (greater effect when combined)
- antagonism (less of an effect when combined)
- indifference (no increase or decrease of an effect when combined)
What are the pharmokinetics of antibacterial action?
- serum conc over time
- penetration to site of infection
What are the pharmacodynamics of antibacterial action?
- susceptibility/potency of a drug
- concentration/time dependent killing
- PAE (post antibiotic effect)
What routes can you give antibiotics?
- topical
- oral
- intravenous
- intramuscular
How do you choose the route and dosage of antibiotics?
using the PK properties of each drug and adverse reactions to decide
What are the differences between antibiotics and vaccines?
Antibiotics: Specificity - usually high Toxicity - potentially high Duration of effect - usually short Duration of treatment - may be prolonged Effectiveness - high
Vaccine: Specificity - very high Toxicity - usually Low Duration of effect - Usually low Duration of treatment - Usually short/may need a booster Effectiveness - Low-moderate
How does antibiotic resistance arise?
-mutations in chromosomal genes (clonal spread of resistant organism)
-acquisition of foreign DNA e.g plasmids this can be caused by:
The spread of a resistant organism
Transfer of plasmids to new strains/species
Mutation in and/or recombination of genetic material
What are the results of antibiotic resistance?
- 120,000 addition surgical site infections and infections after chemotherapy
- 6300 infection related deaths
- longer time to recover from infection
- some drugs no longer effective
- some surgeries/cancer treatments no longer viable due to risk of infection
What happened in the 2011 global call for action?
antibiotic resistance must be seen as a global crisis akin to AIDs appropriate measures must be taken to reduce impacts in a ll areas of human activity
