Antibiotics - Morris Flashcards
How does MRSA acquire resistance?
Acquires SCCmecA
Produces altered PBPs
Beta lactamase inhibitor wont make a difference
Piperacillin - and Pip tazo spectrum of activity
Piperacillin = broad gram negative
PipTazo - Broad gram neg and anaerobes
Gut anaerobes are known for making
Beta lactamase
3rd gen Cephalosporins considered
Extended spectrum Beta lactams
Which carbapenem is very resistant to Pseudomonas?
Ertapenem!
Greatest value of the cephalosporins?
Effective against ESblactamases
Staph aureus resistant first due to
a beta lactamase
Mechanism of action of Vanco - (hint) how is it different from the beta lactams
- Binds directly D-ala D-ala
- Skips the PBPs -
- prevents crosslinking
Because of the size and shape of vanco what can’t it bind to?
Gram negative cell walls
what are some of the toxicities of Vanco?
Renal failure, nephrotoxic
VISA - vancomycin intermediately susceptible Staph - mechanism
Thickened cell wall
reduced access of vanco
VRSA-
Alteration of the D-ala to D-Lac
preventing binding prevent crosslinking
DNA gyrase is a …(type 2 Top)
Topoisomerase 2
- A tetramer
GryA GyrB 2 subunits each
works ahead of the replication fork
Topoisomerase 4 made up of (Type 2 top)
ParC and ParE
Works AFTER the replication fork
In Gram negatives the FQs target mainly…
DNA gyrase - GyrA especially
in Gram positives the FQs target
Topoisomerase 4 - Esp ParC
Moderate level of resistance to FQs occurs when
GyrA is mutated in Gram negs
ParC is mutated in Gram pos
High level resistance to FQs occurs when
Both enzymes mutated
FQ resistance can also be mediated by
- Efflux pumps (on outer cell membrane)
- Gram negatives have porins to reduce accumulation of the drug (also on cell membrane)
TMP-SMX are
Bacteriostatic
block folic acid metabolism (S before T)
Drugs classified as protein synthesis inhibitors
Macrolides Aminoglycosides Tetracyclines Clindamycin Oxazolidinones
Aminoglycosides notorious for there
Nephro and OTOtoxicity
Aminoglycosides - mechanism of action
Bind 30S ribosome
AND
CIDAL - make cell leaky by binding Mg and Ca
They also have a post-antibiotic effect
Which bacteria are most resistant to aminoglycosides?
Gram positives - thick cell wall hard to penetrate
