TABLE 2.
The frequency of inoculum effect among susceptible carbapenemase-producing Enterobacteriaceae isolatesa,b
| Antimicrobial Agent | Total % (n/n) | Metallo-β-Lactamase, % (n/n) |
KPC, % (n/n) | OXA-48-like, % (n/n) |
P-value |
|||||
|---|---|---|---|---|---|---|---|---|---|---|
| All MBL | NDM | IMP | VIM | MBL vs. KPC vs. OXA-48-like | MBL vs. KPC | MBL vs. OXA-48-like | ||||
| Cefiderocol | 95.9 (164/171) | 98.4 (121/123) | 100 (58/58) | 94.5 (37/39) | 100 (26/26) | 88.6 (31/35) | 92.3 (12/13) | 0.027 | 0.022 | 0.262 |
| E. coli (n = 49) | 93.9 (46/49) | 94.6 (35/37) | 100 (16/16) | 88.2 (15/17) | 100 (4/4) | 100 (7/7) | 80.0 (4/5) | |||
| ECC (n = 34) | 100 (34/34) | 100 (34/34) | 100 (24/24) | 100 (10/10) | NA | NA | NA | |||
| K. pneumoniae (n = 74) | 94.6 (70/74) | 100 (38/38) | 100 (13/13) | 100 (5/5) | 100 (20/20) | 85.7 (24/28) | 100 (8/8) | |||
| Aztreonam-avibactam | 95.2 (180/189) | 94.2 (129/137) | 94.2 (65/69) | 92.9 (39/42) | 96.2 (25/26) | 97.4 (37/38) | 100 (14/14) | 0.845 | 0.686 | >0.999 |
| E. coli (n = 50) | 82.0 (41/50) | 78.4 (29/37) | 76.5 (13/17) | 82.4 (14/17) | 66.7 (2/3) | 87.5 (7/8) | 100 (5/5) | |||
| ECC (n = 44) | 100 (44/44) | 100 (44/44) | 100 (31/31) | 100 (13/13) | NA | NA | NA | |||
| K. pneumoniae (n = 79) | 100 (79/79) | 100 (40/40) | 100 (14/14) | 100 (5/5) | 100 (21/21) | 100 (30/30) | 100 (9/9) | |||
a
The inoculum effect was investigated on CPE isolates with a cefiderocol MIC ≤ 4 mg/L or aztreonam-avibactam MIC ≤ 4/4 mg/L at standard inoculum.
b
ECC, Enterobacter cloacae complex; MBL, metallo-β-Lactamase; NA, not applicable.