during this period the mic50 of ampicillin for escherichia coli increased from 8 to 32 micrograms/ml , the mic90 of piperacillin from 16 to greater than 32 micrograms/ml and the mic90 of cefuroxime from 4-8 to 16 micrograms/ml .
C0002680
ampicillin
C0031955
piperacillin