TABLE 1.

MICs of 12 β-lactams for the 12 clinical K. ascorbata isolates, recipient strain E. coli XL-1, and the E. coli XL-1 transformant producing KLUA-1

β-Lactam(s)aNo. of isolates for which MIC (μg/ml) was:MIC (μg/ml) for E. coli XL-1 recipient
<0.030.060.1250.250.51248163264128R+R−
Amoxicillin11442>1284
Amoxicillin + CA3b34211
Ticarcillin2343>1280.5
Ticarcillin + CA5b24140.125
Piperacillin14431281
Piperacillin + TZ4b331120.12
Cephalothin273>1280.5
Cefuroxime165641
Cefoxitin144321
Cefotaxime372128<0.03
Ceftriaxone26414<0.03
Ceftazidime65140.06
Cefepime9214<0.03
Aztreonam46280.12
Imipenem1650.25<0.03
  • a CA, 2 μg of clavulanic acid per ml; TZ, 4 μg of tazobactam per ml.

  • b MIC, <0.125 μg/ml.

  • c R−, E. coli recipient; R+, E. coli with recombinant plasmid producing KLUA-1.