common mechanisms of bacteria resistance Flashcards
When is an organism considered resistant to a given drug?
When it is unlikely to respond to attainable levels of that drug in tissues
Define inherent/intrinsic resistance
when all strains of a species are naturally resistant to an antibiotic
In what two ways is resistance acquired?
- a spontaneous mutation during multiplication of bacterial DNA resulting in change of structure/function
- the gene/genes that code for resistance an spread from organism to organism or species to species.
What two ways can genes be carried between bacteria? (eg when spreading resistance)
Plasmids or transposons
Name the two mechanisms of Beta-lactam resistance
- Beta-lacatamase production
- Alteration of penicillin binding protein (PBP) target site
What are beta lactamases and what do they do?
Bacterial enzymes which cleave the beta lactam ring of the antibiotic and make it inactive
What is a common bacteria in the hospital which produces beta lactamases and is therefore resistant to penicillins/cephalosporins?
Staphylococcus aureus
What are the two ways to combat beta lactamase?
- introduce a second component to the antibiotic - a beta lactamase inhibitor
- modify the antibiotic side chain to create an antibiotic resistant to the enzymes effect
Give an example of two drugs which can treat beta lactamase producing Staph aureus?
co-amoxiclav
flucloxacillin
What are MRSA resistant to?
All penicillins and cephalosporins
How can mutations in PBPs make organisms resistant to penicillins and cepharosporins?
Mutations in penicillin binding protein, result in a modified target site to which beta lactams cannot bind.
What are ESBLs?
Extended spectrum beta lactamases - produced by some gram negative organisms which render them resistant to all beta lactam agents.
Explain the mechanism of glycopeptide resistance
In VREs (vancomycin resistant enterococci), the peptidoglycan precursor to which vancomycin normally binds has an altered structure.
