TABLE 4.

MICs of piperacillin alone and combined with inhibitors for ESBL-producing K. pneumoniae

Enzyme(s)MICa (μg/ml) of piperacillin + inhibitor (4 μg/ml):
TZBABCDEFG
pI 5.4, 5.6, 7.6, and 8.7 enzymes>64>64>64>64646464>64
TEM-1 + SHV-5 + SHV-7>64>6464>6432323232
SHV-13>64168168888
TEM-1 + SHV-1 + SHV-5>6432163216161616
SHV-4644482222
TEM-1 + SHV-2732168168161616
TEM-1 + SHV-53216161616161616
TEM-1 + ACT-1321616161681616
TEM-2616>64166464321632
TEM-9 + SHV-1832166488832
TEM-38168168488
TEM-10 + SHV-1 + SHV8>64166416321632
TEM-10 + SHV-18>64326416321632
CAZ-R, P/T-R strainb enzyme864166416161632
TEM-10432484888
TEM-1 + TEM-26 + SHV-144441616832
SHV-248484888
MIC50 (μg/ml)1632163216161616
MIC90 (μg/ml)>64>64326432321632
% Susceptible5044835083728955
  • a The MICs listed correspond to the inhibitory activity of piperacillin. For each ESBL-producing strain, the MIC of piperacillin alone was >64 μg/ml; none of the isolates were susceptible. TZB, tazobactam.

  • b CAZ-R, ceftazidime resistant; P/T-R, piperacillin-tazobactam resistant.