TABLE 5.

Mutations in ampC promoter and attenuator regions and cephalosporinase specific activity of selected E. coli isolates

StrainMutations in promoter and attenuatoraCephalo- sporinase sp actb
DH5αSame as E. coli K-12 control1.00
EC689−73, −66, −28, +172.59 ± 0.26
EC3076−76, +22, +26, +27, +322.04 ± 0.13
EC3194−76, +22, +26, +27, +322.67 ± 0.12
EC3358No mutations detected2.40 ± 0.09
Control strains
    CDC10−73, −28, 1-bp insert between −35 and −10, +1713.6 ± 2.2
    CDC110−73, −32, +5814.6 ± 1.3
    CDC3100−76, 2-bp insert between −35 and −10, +22, +26, +27, +3217.2 ± 3.7
  • a Key mutations associated with enhanced AmpC production are indicated by bold type.

  • b Specific cephalosporinase activities are relative values based on the activity in the wild type strain DH5α.