A 65-year-old woman who has been in the hos- pital for three weeks receiving cefotaxime to treat Klebsiella pneumonia develops a urinary tract infection. Urine cultures are positive for Enterococcus faecium. Treatment with vanco- mycin is attempted but is unsuccessful. Which of the following aided in this microorganism’s ability to persist despite vancomycin treat- ment?
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(A) Alteration of microorganism’s gyrase
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(B) Methylation of microorganism’s rRNA at a ribosome-binding site
(C) Microorganism’s ability to produce b-lacta- mase
(D) Mutation in terminal amino acid of micro- organism’s cell wall component
(E) Mutation in the microorganism’s penicil- lin-binding protein