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Case 6: Methicillin-Resistant Staphylococcus aureus (MRSA) Skin and Soft Tissue Infections

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A Resistance to methicillin and cephalexin results from production of an altered penicillin-binding protein by S. aureus that has reduced affinity for binding to beta-lactam antibiotics.

This answer is correct. The resistance to methicillin and cephalexin results from the production of an altered penicillin-binding protein (penicillin binding protein 2a) that has reduced affinity for binding to beta-lactam antibiotics. The mecA gene has been identified as the gene responsible for the formation of the altered penicillin-binding protein; the mecA gene is part of a mobile genetic element known as the staphylococcal cassette chromosome mec (SCCmec) that is inserted into the staphylococcal chromosome. The production of beta-lactamase causes resistance to penicillin, but it does not result in methicillin resistance.


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