Fig. 4.

Microbiological assay plate showing inactivation of meropenem (A) (central disk) or imipenem (B) by the OXA-198 enzyme. MH agar plates were inoculated with the carbapenem-susceptible E. coli ATCC25922 strain. A central disk of meropenem (10 μg) or imipenem (10 μg) was put on the dish with 4 satellite disks containing 20 μl of crude sonicated extract of E. coli TOP10 expressing OXA-198 (nitrocefin-specific activity, 1.05 μmol/min/mg) (1), 10 μl of extract (2), 5 μl of extract (3), and 20 μl of phosphate-buffered saline (4). MEM, meropenem; IPM, imipenem.