TABLE 5.

Basal and cefoxitin- and ceftazidime-induced β-lactamase activities of double mutant PAΔDDh3 and triple mutant PAΔDDh2Dh3

StrainAvg β-lactamase sp acta ± SD
BasalCefoxitin (50 μg/ml)Ceftazidime (0.5 μg/ml)Ceftazidime (20 μg/ml)
PAO1152 ± 131.6 ± 0.2NAb
PAΔDDh2Dh3976 ± 165977 ± 1141,050 ± 125995 ± 85
PAΔDDh3210 ± 371,010 ± 35780 ± 641,088 ± 122
  • a Relative values of β-lactamase activity considering 1 the basal activity of reference strain PAO1 (19 nmol of nitrocefin hydrolyzed/min/mg of protein).

  • b NA, not applicable (since the MIC for PAO1 is 1 μg/ml).