Antibiotic resistance Flashcards
Causes of antibiotic resistance:
- Mix of sensitive/resistant bacteria exposed to antibiotics: Sensitive = die Resistant = dominant colonising
- Antibiotic-resistant strains = transferable to other people
Innate resistance mechanism
Usually relates to permeability/entry of the antibiotic into the cell
Acquired resistance mechanism
- Acquisition of a gene that encodes an antibiotic resistance
- New mutation or horizontal transfer
- Usually an antibiotic-modifying enzyme or a target alteration
Decreased permeability resistance
- E.g. Vancomycin and gram negative bacilli. Gram negative have outer cell membrane = impermeable to vancomycin
Target modification resistance
- Flucloxacillin – MRSA - altered penicillin binding protein does not bind β-lactams
Enzymatic degradation resistance
- Gentamicin – aminoglycoside modifying enzymes – inactivate these antibiotics
Drug efflux resistance
Multiple antibiotics, especially gram negative organisms pump drugs back out
Antibiotic era
term used to describe the time since the widespread availability of antibiotics to treat infection
Post-antibiotic era
term used to describe the time after widespread antibiotic resistance has reduced the availability of antibiotics to treat infection
Implications for antibiotic use
Empirical therapy and targeted therapy
Empirical therapy
- treating best guess whilst cultures are tested
- risks of under treatment and risk of excessive broad spectrum treatment if resistant risk used
Targeted therapy
- Requires use of alternatives which may be expensive, toxic or last line.
Monitoring of antimicrobial resistance
- Sensitivity testing: Culture micro-organism in the presence of antimicrobial agent and determine whether MIC is above a predetermined ‘breakpoint’ level – if above it is resistant
Uses of sensitivity testing
- To inform antibiotic therapy
- Provide epidemiological data
worldwide resistance hotspot
- carbapenem resistance in the Indian subcontinent
