Ceftazidime avibactam

Antimicrobial susceptibility testing was carried out in accordance with the Clinical and Laboratory Standards Institute (CLSI) recommendations. The antimicrobial agents cefotaxime, ceftazidime, cefepime, cefoxitin, aztreonam, imipenem, meropenem, ceftazidime/avibactam, gentamicin, amikacin, ciprofloxacin, levofloxacin, sulfamethoxazole/trimethoprim and colistin (Sigma, USA) were used in the test. Antimicrobial susceptibility was determined using breakpoints approved by the CLSI [7] . Standard broth microdilution tests were performed with Mueller–Hinton broth (cation-adjusted; Oxoid Ltd., England) to determine the minimum inhibitory concentration (MIC) of the above antimicrobial agents. Tigecycline (Sigma, USA) was tested using fresh (<12 h) Mueller–Hinton broth. The MIC of cefiderocol (Shionogi, Japan) was determined using iron-depleted cation-adjusted Mueller–Hinton broth (ID-CAMHB) prepared with Chelex® 100 resin (Bio-Rad Laboratories, USA). For quality control, E. coli ATCC 25922 was used. As there are no CLSI breakpoints for Tigecycline, the FDA standard was adopted. The EUCAST guidelines were used to interpret the colistin MIC.