Table 3.

Susceptibilities of constructed mutants to β-lactams

Antimicrobial agentMIC (μg/ml)a
N116N151N119N153N133N154
Penicillins
 Penicillin G5120.13160.0610.13
 Cloxacillin>4,096644,096451264
 Nafcillin1,02482560.25328
 Amoxicillin640.1310.130.50.13
 Piperacillin80.0610.060.50.06
 Carbenicillin1280.250.250.250.250.25
 Sulbenicillin640.250.250.250.250.25
Cephems
 Cefamandole8,19222560.5322
 Cefuroxime4,09622560.25162
 Cefoperazone160.1320.0610.13
 Cefotaxime640.0620.0610.06
 Ceftizoxime1280.0620.0320.06
 Ceftriaxone160.2510.1310.13
 Cefsulodin40.250.50.130.50.25
 Ceftazidime20.250.250.250.50.25
 Cefpirome40.25160.0680.25
 Cefepime20.0620.0320.06
 Cefozopran20.2580.1340.25
 Cefoselis20.1340.0340.13
 Cefoxitin5120.580.1320.5
Oxacephems
 Moxalactam320.50.50.511
 Flomoxef1280.2520.250.50.25
Carbapenems
 Imipenem0.250.50.130.250.50.5
 Meropenem10.0160.130.0160.060.016
 S-46610.50.030.130.030.250.03
Monobactam, Aztreonam320.130.130.130.250.25
  • a N116 produced MexAB-OprM, N119 produced MexCD-OprJ, N133 produced MexXY-OprM, and N151, N153, and N154 were deficient in the three efflux systems.