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6 Cards in this Set

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Regarding alterations of critical enzymes, beta lactam antibiotics inhibit bacteria by binding covalently to penicillin binding proteins(PBPs) also called transpeptidases in the cytoplasmic membrane. TRUE/FALSE
TRUE. These target proteins are necessary for the synthesis of the peptidoglycan that forms the cell wall of bacteria.
What is the result of PBP alteration?
Alterations of PBPs that prevent successful binding can lead to beta lactam resistance.
How is Gram + bacteria influenced by PBP alteration?
In G+ bacteria, resistance to beta lactam antibiotics may be associated either with a decrease in the affinity of the PBP for the antibiotic or with a decrease in the number of PBPs produced by the bacterium.
Regarding the bypass of antibiotic inhibition, how is this related to auxotrophs?
Another mechanism for acquiring resistance to specific antibiotics is by the development of auxotrophs, which have growth factor requirements different from those of the wild strain.
These mutants require substrates that normally are synthesized by the target enzymes and thus, if the enzyme is blocked and the substrates are present in the environment, the organisms are able to grow despite inhibition of the synthetic enzyme.
Why is the auxotroph bypass mechanism particularly concerning?
Because bacteria are able to create additional pathways to meet growth requirements in response to a particular pathway being blocked by the antibiotic.
Can you give an example of the above mechanism?
Thymidine dependent bacteria like enterococci are able to utilize exogenous supplies of thymidine for enzyme activity and are thus highly resistant to trimethoprim which blocks endogenous production of thymidine by bacterial enzymes.