Antimicrobial resistance - Dr Becker Flashcards
What is the clinical definition of resistance?
Bacterial ability to survive antimicrobial therapy and cause therapeutic failure
What is the microbiological definition of resistance?
bacterial strains that survive at higher antibiotic conc. compared to wild type population (those without resistance genes)
What are the different resistance strategies that bacteria use?
- Stops antibiotic from reaching target
- Modifies or bypasses the target
How do bacteria stop antibiotics from reaching the target?
- Efflux pumps
- Decrease permeability of cell wall
- Destroys antibiotic by producing bacterial enzymes
- Modifies the antibiotic by adding dif. chemical groups
How do bacteria modify or bypass the target?
- Camouflage
- Express alternative proteins
- Reprogram target
“Shoot High”
Use highest possible dose
For conc. dependent drugs, to enhance efficacy
“Shoot Regular”
Administer drug at time intervals
For time dependent drugs, to enhance efficacy
Inform owner of importance of compliance
” Shoot Fast”
treat early and for the shortest time possible
What are examples of MIAs?
Medically important antimicrobials
- 3rd and 4th gen cephalosporins
- Macrolides
- Fluproquinolones
These are critically important drugs and only used for life threatening situations
MRSA
Methicillin Resistant Staph. Aureus
- Gram + skin commensal
- Has mecA gene encoding penicillin binding proteins (PBPs)
-Low affinity to most B lactams
-Major role in nosocomial infections
Acquired in hospitals, livestock, and communities
MRSP
Methicillin Resistant Staph. pseudintermedius
- Gram + skin commensal in dogs
- mecA resistant gene
-Multi drug resistant bacteria leading to therapy failure
Acquired from POST SURGICAL wound infections
ESBL
Extended Spectrum Beta Lactamase
- Makes enterobacteriaceae
- Gram neg bacteria that can hydrolyze and inactivate beta lactams
- High risk for food borne transmission, effects gut commensal
What is antibiotic selection?
Bacteria with acquired resistance pass it to other bacteria
Antibiotics will kill suseptible bacteria while resistant bacteria continues to multiply and cause infection
What is intrinsic resistance?
Naturally acquired
Species specific (to gram neg or gram pos)
What is acquired resistance?
Resistance by mutation in existing DNA
or by transformation, transduction, or conjugation of new DNA
