Bacterial Genetics & Antibiotic Resistance Flashcards
What targets do antibiotics have?
Inhibit cell wall synthesis Inhibit peptidoglycan synthesis Inhibit protein biosynthesis Inhibit DNA and RNA replication Inhibit folate metabolism (bacteria produce folate while we need it in diet)
What does penicillin do?
Inhibits synthesis of cell walls and proteoglycan
What do macrolides and streptogramins do?
Inhibit protein biosynthesis
What does rifampicin and ciprofloxacin do?
Inhibits DNA and RNA replication (unwinds DNA)
What are the major biochemical mechanisms of resistance?
Mutation of drug target Breakdown of antibiotic Modification of antibiotic Efflux of antibiotic Plasmid transfer Transposable elements Resistance genes by transformation
What is an example of an antibiotic which obtains resistance from mutation of the drug target and how does it do it?
Rifampicin - normally inhibits RNA polymerase but this will undergo several different mutations
What is the consequence of rifampicin resistance?
- TB use combination with other drugs
- TB limit to prophylaxis
- can also mean target site is not resistant to streptomycin and ciprofloxacin
What is an example of an antibiotic which obtains resistance from breakdown of an antibiotic and how?
- beta lactam
- normally inhibits cell wall synthesis
- bacteria acquire new gene and degrade beta lactam
What is an example of an antibiotic which obtains resistance from antibiotic modification and how?
- aminoglycoside
- bacteria acquire the genes encoding the antibiotic modifying enzymes and add small molecules to them so don’t bind
What is an example of an antibiotic which obtains resistance from efflux and how?
- tetracycline
- chloramphenicol
- fluoroquinolones
- beta lactams
- bacteria can upregulate existing pump by mutation or acquire genes for new pump
How does plasmid transfer occur?
- To acquire new genes
- from one cell to another
- involves replication
What is a transposon?
- sequence that can change its position in a genome
- encode transposase gene required for insertion and excision
What is the difference between simple and complex transposons?
- simple carry additional genes
- complex are multiple genes with multiple copies
What are integrons?
- element carrying multiple resistance genes
- transfer whole set of resistance genes together
How does transformation occur?
- transfer naked DNA
- released from lysed bacterial cell
- via homologous recombination
- e.g. strep pneumoniae penicillin resistance
