TABLE 1.

β-Lactam susceptibility and β-lactamase activity of TEM-1- and TEM-30 (IRT-2)-producing E. coli transformants according to the type of promoter upstream from the blaTEM-1B and blaTEM-30B genes

Strain and blaTEM gene (promoter)MIC (μg/ml)aβ-Lactamase activity (U/mg) (mean ± SD)
AMC (≤4->16)TIC (≤16->64)TCC (≤16->64)PIP (≤8->64)TZB (≤8->64)CEP (≤8->32)
E. coli
    ATCC 25 922444218NDb
    NM554222112ND
Transformant NM554
    blaTEM-1B (P3)328,19232128186.8 ± 3.3
    blaTEM-1B (Pa/Pb)128>8,19225651223213.8 ± 2.1
    blaTEM-1B (P4)512>8,1921,0241,0241286438 ± 9
    blaTEM-1B (P5)1,024>8,1922,048>1,02451212887.4 ± 8
    blaTEM-30B (P3)2561283281814 ± 4.4
    blaTEM-30B (Pa/Pb)2,048512128642832.6 ± 5.6
    blaTEM-30B (P4)4,0962,04851264328120 ± 7.9
  • a Drug abbreviations: AMC, amoxicillin with 2 μg of clavulanate per ml; TIC, ticarcillin; TCC, ticarcillin with 2 μg of clavulanate per ml; PIP, piperacillin; TZB, piperacillin with 4 μg of tazobactam per ml; CEP, cephalothin. The MIC breakpoints (in micrograms per milliliter) are shown in parentheses after the drug abbreviations.

  • b ND, not determined.