TABLE 2.
Results of antimicrobial susceptibility testing with ceftazidime-avibactam (CZA), ceftolozane-tazobactam (C/T), and cefiderocol (FDC) for 66 Pseudomonas aeruginosa isolates stratified by MRGNa classification
| Total or MRGNa type (n) | MIC50b |
MIC90b |
No. (%) of isolates susceptiblec |
||||||
|---|---|---|---|---|---|---|---|---|---|
| CZA | C/T | FDC | CZA | C/T | FDC | CZA | C/T | FDC | |
| Total (66) | 8 | 4 | 1 | >256 | 96 | 6 | 31 (47) | 34 (52) | 46 (70) |
| Non-MRGN (18) | 4 | 3 | 0.25 | 16 | 12 | 3 | 16 (89) | 15 (83) | 16 (89) |
| 3-MRGN (10) | 4 | 4 | 0.25 | 64 | 24 | 6 | 6 (60) | 7 (70) | 8 (80) |
| 4-MRGN (38) | 32 | 12 | 2 | >256 | >256 | 8 | 9 (24) | 12 (32) | 22 (58) |
MRGN (multidrug-resistant Gram-negative) bacteria are classified according to KRINKO (the German Commission for Hospital Hygiene and Infection Prevention) as unsusceptible to the lead compounds of 3 (3-MRGN) or 4 (4-MRGN) of the following antibiotic classes: acyl ureidopenicillins (piperacillin-tazobactam or piperacillin), third- or fourth-generation cephalosporins (ceftazidime and cefepime), fluoroquinolones (ciprofloxacin), and carbapenems (meropenem and imipenem) (12).
MIC50/90 is defined as the MIC in micrograms per milliliter at which 50%/90% of isolates were inhibited, respectively.
Susceptibility breakpoints determined by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) were 8 μg/mL for CZA, 4 μg/mL for C/T, and 2 μg/mL for FDC, respectively.