Unit 8 Antimicrobial Chemotherapy Flashcards
(55 cards)
Antimicrobial activity is the ability to
Produce the death of the organism
Or
Prevent the development and multiplication of microorganisms
Antimicrobial
Substance with Antimicrobial activity that can be used for the treatment of infectious diseases because of its effectiveness and lack of toxicity
Categories Antimicrobial
Antibacterial
Antiviral
Antifungal
Antiparasitic
Selective toxicity
Harms the microorganisms but not the human cells
Therapeutic target
The structures we target in order to kill a microorganism like it’s fundamental structures
Characteristics we aim for Antimicrobial
Minimum toxicity for the host
Active at low concentration
Antimicrobial activity
Narrow spectrum
Selectively active on some species
Broad spectrum
Active against large number of microorganisms
Bacteriostatic
Inhibit the growth of microorganisms
The performance of the patient’s defense mechanisms in essential here
Bactericidal
Kills the microorganisms
Depends on the concentration, if it’s low it could be static
Mechanism of action
The specific biochemical interaction through which an antimicrobial produces its pharmacological effect.
Why an antibiotic might not work against a bacteria
Depends on the structure of the bacteria and the mechanism of action
Mode of action of B-lactam
Bind to the proteins PBP involved in cell wall synthesis
Efficacy of antibiotics depends on
A target for the antibiotic must exist
Antibiotic shouldn’t be inactivated or modified
Sufficient amount of antibiotic must reach the target
Two types of antibiotic resistance
Intrinsic : possessed by all the bacteria of a specie by innate genetic characters.
Acquired : by certain individuals of a specie due to chromosomal mutations, selective pressure or horizontal transmission
How is the resistance of an antibiotic passed to the whole population
-Horizontal transmission
-selective pressure
-mutation
and selection by the use of antibiotics by killing the sensitive population and leaving the mutant
Antibiotic resistance by inactivation : 3 mechanisms
Hydrolysis
Transference of a chemical group
Reduction/oxidation
Resistance by modification of the target exemples
Alteration of peptidoglycan structure
Modification of PBPs
Interference with protein synthesis
Mutation in rRNA
Interference with DNA synthesis (mutation in gyrase and topoisomerase)
Resistance by active efflux pump
Expel antibiotics outside of the cell
Different level of specificity
Can affect all classes of antibiotics
Produce a low level resistance
Reduction of permeability
Can generate resistance to what
Affects the transport through the outer membrane
Due to changes in the number, size or specificity of the porins
Can generate resistance to hydrophilic b-lactam and fluoroquinolone
Low level resistance
Mechanisms of bacterial resistance
Modification of the target
Reduced permeability to antibiotics
Active efflux pump
New metabolic pathways
Enzymatic inactivation
The mechanisms of resistance to b-lactam antibiotics are
Destruction by b-lactamase
Modification of the target PBPs, no recognition
Reduction of permeability
Efflux pumps
How do b-lactamase works
When is it the most effective
Break the b-lactam ring. More effective in gram- because Periplasmic space is bigger
Enterobacteriaceae (type of b-lactamase)
TEM 1
Extended spectrum b-lactamase
Carbapenemase
