Fig. 4
From: A novel family VIII carboxylesterase hydrolysing third- and fourth-generation cephalosporins
Disc diffusion assay for confirming the hydrolysis of antibiotics by EstSTR1. This assay was performed by incubating purified EstSTR1 with antibiotics, including 3 mM cephalothin, 1 mM cefoxitin, 1 mM cefotaxime, and 1 mM cefepime in 50 mM Tris–HCl (pH 8.0) for 2 h at 35 °C. The reaction mixtures were adsorbed onto a paper disk and placed on agar seeded with E. coli BL21(DE3). The diameters of the inhibition zones around the discs appeared after an 8 h at 37 °C. The negative controls were samples containing antibiotics only and the positive controls were reaction mixtures containing CMY-10 and antibiotics. Antibiotics: LOT cephalothin, FOX cefoxitin, TAX cefotaxime, FEP cefepime