FIG 2 .

Effects of TZP on E. coli 907355 Bla_TEM-1 levels and β-lactamase enzyme activity. (A) Detection of Bla_TEM-1 in E. coli ATCC 25922 (lane 2), ATCC 35218 (lanes 3 to 5), and 907355 (lanes 6 to 9) by Western immunoblotting. Strains were cultured in medium containing no antibiotic (lanes 2, 3, and 6), 4 µg/ml tazobactam (lanes 4 and 7), 4 µg/ml piperacillin (lanes 5 and 8), or 4/4 µg/ml TZP (lane 9) prior to protein sample collection. Molecular mass standards are shown in lane 1 (kilodaltons are indicated to the left of the blot). The estimated molecular mass of Bla_TEM-1 is 31.5 kDa. This experiment was repeated on independently collected samples and yielded similar results. (B) Determination of Bla_TEM-1 activity in E. coli 907355 via a nitrocefin hydrolysis assay after growth in the presence or absence of 4/4 µg/ml TZP. ATCC 35218 Bla_TEM-1 activity is included as a comparison but was not determined (ND) in the presence of TZP due to lack of growth. Units on the y axis denote the micromoles of nitrocefin hydrolyzed per milligram of total protein per minute. The values above each bar on the graph represent the means of 3 experiments, and the error bars indicate the standard deviations of the means.