TABLE 4.

Levels of β-lactamase specific activity under basal and cefoxitin-induced conditions

StrainAvg β-lactamase sp acta ± SD
BasalInducedb
PAO12.8 ± 0.4230 ± 20
PAΔnagZ3.9 ± 0.895 ± 7.8
PAΔDDh2Dh33,792 ± 1213,935 ± 11
PAΔDDh2Dh3nagZ288 ± 321,019 ± 64
  • a Specific activity is in units of nanomoles of nitrocefin hydrolyzed per minute per milligram of protein.

  • b Induction was carried out by culturing the strains in the presence of 50 μg/ml cefoxitin for 3 h 37°C.