TABLE 3.

β-Lactamase activities for various strains tested

StrainGeneβ-Lactamase activitya
Without cefotaximeWith cefotaxime
Xc11blaXCC-13,670 ± 803,550 ± 144
Xc11RMblaXCC-17 ± 2ND
Xc11RM(pFJ-ampR1)blaXCC-13,200 ± 443,120 ± 25
Xc17blaXCC-104,190 ± 304,150 ± 78
Xc6blaXCC-113,590 ± 723,320 ± 89
Xv64blaXAV-110,000 ± 889,960 ± 58
Xv3240Unknownb38 ± 18ND
Xcm38c28 ± 7ND
Sm6blaSM-11,590 ± 715,890 ± 147
  • a The specific activity of the β-lactamase is defined as nanomoles of nitrocefin hydrolyzed per minute per milligram of protein and the mean ± standard deviation is shown for each strain. Cells were grown without cefotaxime or with cefotaxime at a final concentration of 8 μg/ml. ND, not determined.

  • b Presence of the gene not determined.

  • c —, no blaXCC-1 homologue detected by Southern hybridization.