TABLE 3.

Complementation of the AmpC hyperproduction phenotype of the PAO1 ampD mutant (PAΔD) with plasmids harboring wild-type ampD (pUCPAD), ampDE (pUCPADE), ampDh2 (pUCPADh2), and ampDh3 (pUCPADh3)

StrainCeftazidime MIC (μg/ml)Avg β-lactamase sp acta ± SD
BasalInduced
PAO11152 ± 13
PAΔD876 ± 18250 ± 45
PAΔD(pUCP24)860 ± 21260 ± 52
PAΔD(pUCPAD)11.7 ± 0.989 ± 32
PAΔD(pUCPADE)11.4 ± 0.639 ± 14
PAΔD(pUCPADh2)11.5 ± 0.573 ± 25
PAΔD(pUCPADh3)12.7 ± 1.338 ± 16
  • a Relative values of β-lactamase activity considering 1 the basal activity of the reference strain PAO1 (19 nmol of nitrocefin hydrolyzed/min/mg of protein). For induction experiments, the strains were grown in the presence of 50 μg/ml cefoxitin for 3 h.