Antimicrobial Therapies Flashcards
What is an antibiotic?
Antimicrobial agent produced by a microorganism that kills or inhibits other microorganisms
What does Antimicrobial mean?
Chemical that selectively kills or inhibits microbes
What does bactericidal mean?
Kills bacteria
What does bacteriostatic mean?
Stops bacteria growing
What does antiseptic mean?
Chemical that kills or inhibits microbes
Usually used topically to prevent infection
When is a bacterium considered resistant?
When it can grow at or above the breakpoint of the antibiotic conc. required to inhibit growth
What is the breakpoint?
Estimate of the clinically achievable conc of a given antibiotic in a host tissue
How does AB resistance lead to increased mortality, morbidity and cost?
Increased time to effective therapy
Requirement for additional approaches - e.g surgery
Use of expensive therapy (newer drugs)
Use of more toxic drugs e.g vancomycin
Use of less effective ‘second choice’’ antibiotics
What is the difference between positive and negative gram bacteria?
Gram-negative has 2 membranes but gram-positive has 1
What are the 4 distinct mechanisms of antibiotic resistance?
Altered target site
Inactivation of antibiotic
Altered metabolism
Decreased drug accumulation
What happens during the altered target site mechanism?
Acquisition of alternative gene —> drug no longer binds where
it wants to
Gene that encodes a target-modifying enzyme
What happens during the inactivation of antibiotic mechanism?
Enzymatic degradation or alteration —> rendering antibiotic
ineffective
—> enzyme cleaves antibiotic —> stops working
What happens during the altered metabolism mechanism?
Increased production of enzyme substrate can outcompete antibiotic inhibitor
Bacteria switch to other metabolic pathways
—> re-routes metabolism or massively increase expression of target
—> need more drug to inhibit it
—> may not be possible to give person that much drug
What happens in the decreased dug accumulation mechanism?
Reduced penetration of AB into bacteria cell or increased effluent of AB out of the cell
—> drug does not reach concentration required to be effective
What are the sources antibiotic resistance genes?
Plasmids —> can be moved around easily
Transposons —> can shuttle DNA
Naked DNA —> take up DNA from decade bacteria released into environment
