Antibacterial agent 58 (example 23) significantly lowers MIC value of Ceftazidime (MIC=1, 2, 8 mcg/ml for E. coli NCTC 1335 1, E. coli M50, and E. coli 7MP, respectively). Antibacterial agent 58 significantly lowers MIC values of the antibacterial agent Ceftazidime (MIC=0.2~2 mcg/ml for class A ESBL; 2-8 mcg/ml for class C ESBL; 4-8 mcg/ml for KPC ESBL)[1]. From WO2013030735A1, example 23. Class A ESBL: E.coli W 13353; E.coli W3351; E.coli W 13352 Class C ESBL: E.coli M 50; E.coli 7 MIP; E.coli B 89 KPC ESBL: K.pneumoniae H 520; K.pneumoniae H 521; K. pneumoniae H 522 Class D ESBL: A.Baumannii13301; A.baumannii 13304