Antibiotic Resistance Flashcards
Define resistance?
Development of organism’s defences against chemotherapeutic agents leading to restriction of medical treatment of many infections
How is antibiotic resistance acquired?
Chromosomal mutation
R plasmids carrying resistance genes
Transfer of R genes within bacterium by transposons
What are integrons?
Genetic elements that contain genetic components mediating site-specific recombination that recognise and capture mobile gene casettes
What do integrons posses?
Site specific recombinase and specific recombination sites
What are integrons most commonly carried on?
Plasmids either directly or inserted in a transposon
What are gene cassettes?
Consist of a resistance gene attached to a recognition site
What is conjugation?
Resistance transfer by physical contact between bacteria via pili
What is transduction?
Plasmid enclosed in a bacterial phage and transferred to another bacteria of same species
What is transformation?
Naked DNA taken up by bacteria from the enviroment by cross-over mechanism
What are four main biochemical mechanisms of resistance?
- Enzymatic inactivation of the drug
- Altered drug binding site
- Decreased drug accumulation
- Development of alternative resistance pathways
What do beta lactamases inactivate?
Penicillins and cephalosporins
How are beta lactamases acquired?
Encoded on plasmids by transduction in Staph
Chromosomal or plasma mediated in gram -ve bacteria
What are 3 solutions to beta lactamases?
- Co-administer antibiotic with B-lactamase inhibitors
- Use semi-synthetics
- Use monobactams or carbapenems
What does acetyltransferase inactivate?
Chloramphenicol
What is acetyltransferase encoded by?
Plasmids
What does phosphorylation/adenylation/acetylation inactivate?
Aminoglycosides
What are phosphorylation/adenylation/acetylation encoded by?
Resistance genes carried on plasmids and transposons
What are 5 drug binding sites that can be altered?
30S
50S
Point mutation of DNA gyrase A
RNA polymerase
B-lactam binding site
How can decreased drug accumulation be achieved? (4 ways)
Increasing efflux pumps
Inhibiting porin synthesis
Altering permeability due to chromosomal mutations in polysaccharides
Mutations of envelope components
What is the main cause for antibiotic resistance?
Misuse of antibiotics
What are 4 future treatments of bacterial infections?
- use of mutated bacteria to compete
- Use of compounds which destroy biofilms
- use of urinary tract anti-septics
- use of bacteriophage lytic enzymes
