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Antibiotics and Antibiotic Resistance - Coggle Diagram
Antibiotics and Antibiotic Resistance
Antimicrobial chemotherapy
selective toxicity - needs to be toxic to bugs, not us
The therapeutic index helps us to do this -
high is good
Therapeutic index = Toxic dose to us / therapeutic dose against bugs
Allergenicity is another topic that is unrelated
Types of antibiotics
bacteriocidal - kills bacteria (irreversible
bacteriostatic - stops growth (reversible)
Minimum Inhibitory Concentration (MIC)
is lowest dose for stasis (most commonly reported)
Spectrum of therapy
Broad spectrum
good for unknown bacterial agent with serious effects
Narrow spectrum
good for known bacterial agent
Mechanisms of resistance
Enzymatic modification or degradation
β-lactamase cleaves cleaves β-lactams
clavulanic acid
inhibits β-lactamase
Augmentin is amoxicilling with clavulanic acid
aminoglycoside phosphotransferase
an enzyme phosphorylates the antibiotic to change the charge so it doesn't work anymore
Alter the target of the antibiotic
spontaneous mutation
enzymatic modification
methylation of rRNA (erythromycin is affected by this)
new biosynthetic pathway yields altered target (vancomycin is affected by this)
Less common methods
change flux of antibiotic
Pumping the antibiotics right out of the cell (tetracycline [doxycycline]) affected by this - results in decreased uptake
MAR pumps are issues that cause antibiotic resistances
innate resistance (inherent to the bacteria)
Permeability barrier of gram neg bacteria
lack of peptidoglycan in Mycoplasma (wall less bacteria)
acquire genes for new enzymes that are resistant
Methicillin is affected by this in a resistant S. aureus some 3000 years ago (penicillin binding proteins permanently changed in chromosome)
Genetics of resistance
antibiotic resistance plasmid
need a new enzyme to do something - that requires a plasmid
chromosomal point mutation
protein target changed, now isn't recognized by antibiotic
R (resistance) plasmids
Multiple resistance genes
Spontaneous point mutations
If the patient has a high bacterial load, a rare resistance mutant can arise (highly relevant for tuberculosis)
weird case
Penicillin resistance of Streptococcus pneumoniae