TABLE 2

Antibiotic susceptibilities of E. coli strains, combination CAZ-AVI, and effect of PMBN

StrainMIC (mg/liter)a
CHLPAβNNORNALCIPPIPAVIPMBNCAZCAZ + AVI 1CAZ + AVI 2CAZ + AVI 4CAZ + PMBNAVI + PMBNCAZ + PMBN + AVI 1CAZ + PMBN + AVI 2CAZ + PMBN + AVI 4CPTIPMMEMATMERT
AG10085120.12540.032165120.50.250.250.250.0380.030.03ND0.1250.1250.020.1250.02
ARS1002565121,024>1,02464>1,024128>1,02410.50.50.250.12580.060.030.03320.250.0682
ARS1085122561,024>1,024256>1,024321,0243210.50.25280.030.030.03>1280.250.25>1284
ARS14432256512>1,024128>1,02481,0241,0248823280.50.50.5>1280.250.06>1280.5
ARS1508256>1,024>1,0245121,02481,024512212480.1250.02ND>1280.50.06>1282
ARS23764256512>1,0241281,024321,024128210.06280.030.03ND>1280.1250.5>1284
ARS2731,024512512>1,02464>1,02485121283210.25840.030.02ND>1280.251>1288
ARS30116512512>1,024256>1,024161,0242,0483216832160.50.5ND>1280.250.03>1282
  • a CHL, chloramphenicol; PAβN, phenylalanine-arginine β-naphthylamide; NOR, norfloxacin; NAL, nalidixic acid; CIP, ciprofloxacin; PIP, piperacillin; AVI, avibactam (1, 2, or 4 mg/liter); PMBN, polymyxin B nonapeptide (used at MIC/10 for combination); CAZ, ceftazidime; CPT, ceftaroline; IPM, imipenem; MEM, meropenem; ATM, aztreonam; ERT, ertapenem; ND, not determined because of intrinsic susceptibility preventing the reading of a reliable endpoint.