Table 2

Characterization of isogenic susceptible-PBLR P. aeruginosa clinical isolates

PatientIsolateaTreatment before emergence of resistancebMIC (μg/ml)bResistance mutation(s)cExpression of resistance gened:
CAZFEPPTZATMIMPMERTOLampDdacBoprDampC basalampC inducedemexBmexFmexDmexY
53-B7TOB, CIP, PTZ, IMP188820.120.25WTWTWT<5199<2<5<58.3
3-F41286412825664644D28GG427DT276A; W278X2,1124,143<2<51314
73-A2IMP, CIP, PTZ, TOB122420.120.12WTWTWT<51,218<2<5<5<5
3-D81286412812864644WTG366S; A394PNo OprDf1,3512,84626<5<5<5
81-H9PTZ, CAZ, TOB8883264640.5WTWTΔoprD<52504.0<5<5<5
2-A11283212812864644Ins. 1 bp (C) in 481T428PΔoprD1,7223,0586.5<5<5<5
141-A10TOB, CIP, IMP,CAZ11443220.5WTWTW339X<5200<2<5<5<5
1-C532161283264641Q155XWTW339X3172,26714<5<521
162-G5FEP, TOB, IMP, CIP, CAZ1441610.120.5WTWTWT<5536<2<5<5<5
2-I41281281286464642ΔampDEM200I; del D201ΔoprD1,4383,388<2<5<512
173-D9IMP, PTZ228820.250.5WTWTWT<5443<2<5<5<5
3-F51664643264160.5V10GWTNoOprDf671,068<2<5<5<5
  • a Resistance mechanisms for strains 2-A1, 1-C5, and 2-I4 had been previously partially characterized (17, 25).

  • b TOB, tobramycin; CIP, ciprofloxacin; PTZ, piperacillin-tazobactam; IMP, imipenem; CAZ, ceftazidime; FEP, cefepime; ATM, aztreonam; MER, meropenem; TOL, ceftolozane.

  • c WT, wild-type sequence.

  • d Relative mRNA expression compared to wild-type PAO1. According to previous works (4), breakpoints used to define overexpression were ≥10-fold for ampC, mexF, mexD, and mexY (5 to 10 borderline) and ≥3-fold for mexB (2 to 3 borderline).

  • e Induction experiments were carried out with 50 mg/ml cefoxitin.

  • f Although these strains showed a wild-type oprD sequence, OprD was not expressed when outer membrane proteins (OMPs) were analyzed through SDS-PAGE.