Mechanisms of Antimicrobial Resistance Flashcards
Sources of mechanisms of resistance (2)
Innate vs. acquired
Do antibiotics cause resistance?
No, they select for it in bacterial populations
How do bacteria acquire new genetic information?
Transduction, transformation, conjugation
Targets for antimicrobial action (5)
- Folate metabolism
- DNA synthesis
- Protein synthesis
- Cell wall synthesis
- Cell membrane
Mechanisms for antimicrobial action (5)
- Folate metabolism INHIBIT
- DNA synthesis INHIBIT
- Protein synthesis INHIBIT
- Cell wall synthesis INHIBIT
- Cell membrane DISRUPT
How many mechanisms of antimicrobial action does each antibiotic typically have?
One
How many mechanisms of resistance can overcome each antimicrobial action?
Multiple
How many mechanisms of resistance does each bacteria possess?
Multiple
Mechanisms of Resistance (5)
- Altered targets
- Bypass inhibited pathway
- Antibiotic inactivation
- Decreased influx
- Increased efflux
PBP enzyme mutations
- example of altered target resistance
- mecA gene in MRSA encodes PBP that can’t be bound by abx
- beta lactam resistance
Ribosomal subunit protection
- example of altered target resistance
- tetracycline resistance, similar mechanisms in aminoglycosides and lincosamides
- tetM and tetO encode proteins that alter ribosomal subunit conformation, preventing binding
Altered gyrase/topoisomerase
- example of altered target resistance
- quinolone resistance
- gyrA, gyrB, gyrC encode proteins that can’t be bound by fluoroquinolones
Altered peptidoglycan precursor
- example of altered target resistance
- vancomycin resistance
- vanA allows VRE to produce different peptidoglycan precursor that can’t be bound by abx
DHPS or DHFR mutations
- example of altered target resistance
- TMP-SMX can’t bind enzyme and inhibit them
Folate scavenging
- example of bypassing pathway resistance
- Enterococcus can salvage folate from environment
- resistance to TMP-SMX
