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6 Cards in this Set
- Front
- Back
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What is Minimum Inhibitory Concentration and how can it be determined?
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Lowest Concentration of an antimicrobial required to inhibit visible growth of the microorganism.
Measured by: Agar Dilution Epsilometer Test Disk Susceptibility Test |
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Define Cmax
Define Breakpoint |
Cmax = maximum concentration that a drug achieves in the tested area after administration
Breakpoint - Point when bacteria will not respond. Breakpoint = MIC |
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Penicillins are most effective on which type of bacteria?
What is their mechanism of action? |
Gram positive bacteria (although some semi-synthetic penicillins have action against gram -ve)
Inhibit cell wall synthesis via interaction with transpeptidation reaction. Bind to transpeptidase enzymes (PBPS) and inhibit their action. No transpeptidation = no cell wall cross-linking = poor cell wall which cannot maintain strength. AB-PBP complex also releases autolysins to digest existing cell wall |
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How does MIC increase following mutations in PBPs?
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Single mutation - slight increase in MIC
Multiple mutations - MIC creep Construction of mosaic PBP genes - speeds up increase in MIC *Mosaic gene - contains genes from many organisms |
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What is natural competance?
Name two bacterial species which are naturally competant |
Ability to take up naked linear DNA from environment
S. pneumoniae and H. influenzae =mechanism by which mutations may be passed from one cell to another |
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What is a B Lactamase?
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An enzyme produced by bacteria which provides resistance to B lactam antibiotics
Lactamase enzyme breaks open the 4 membered B Lactam ring of B Lactam antibiotics deactivating the drugs antimicrobial properties |
