TABLE 1.

β-Lactamase expression and MICs of ceftazidime against selected P. aeruginosa isolates before and after complementation with ampD

IsolateSourceaampD genotypebCeftazidime MIC (μg/ml) before/aftercampD complementationβ-Lactamase activity (mU) before/aftercampD complementation
BasalInduced
PAO1Reference+0.064/0.06424/22218/152
PA258Clinical64/1.0010,100/2712,000/1,500
17107BClinical100/0.25504/10947/345
17107B-1Variant, in vivo>256/0.751,090/144,120/521
17107B-2Variant, in vivo>256/0.381,560/2.42,260/223
17107B-3Variant, in vivo>256/89,160/347,950/177
17107B-4Variant, in vivo>256/1.0012,000/912,600/288
19676AClinical+50/−38/−957/−
19676A-1Variant, in vitro+200/−687/−2,200/−
19676A-2Variant, in vivo+96/9611,000/7,81012,700/11,400
19676A-3Variant, in vivo+>256/>25617,300/13,50016,700/16,000
PAO579Clinical+0.8/−19/−550/−
PAO579-1Variant, in vivo+12.5/−114/−275/−
PAO579-2Variant, in vitro+200/−984/−627/−
PAO579-3Variant, in vitro+200/−1,130/−647/−
  • a Variants from in vivo and in vitro biofilm experiments have previously been published (1).

  • b +, ampD gene present; −, ampD gene interrupted by insertion of IS1669.

  • c Before, isolates transformed with pNB100; after, isolates transformed with pNB101. A “−” sign indicates no transformation was performed with pNB101. One milliunit of β-lactamase is defined as 1 nmol of nitrocefin hydrolyzed per min per mg of protein.