TABLE 4.
Ability of β-lactamase inhibitors to reduce MICs of study drugs ≥8-fold in tests with E. cloacae, E. aerogenes and C. freundii
| Druga | Inhibitorb | No. of isolates with reduced MIC requirement in β-lactamase group (no. of strains tested)c:
|
||
|---|---|---|---|---|
| ESBL (16) | AmpC (17) | OBL (15) | ||
| CAZ | C1 | 8 | 0 | 0 |
| C2 | 9 | 0 | 0 | |
| C4 | 9 | 0 | 0 | |
| S8 | 10 | 2 (2)d | 0 | |
| CTX | C1 | 10 | 0 | 0 |
| C2 | 10 | 0 | 0 | |
| C4 | 11 | 0 | 0 | |
| S8 | 14 | 3 (3) | 1 (1) | |
| CTR | C1 | 11 | 0 | 1 |
| C2 | 10 | 0 | 1 | |
| C4 | 12 | 0 | 0 | |
| S8 | 15 | 2 (2) | 0 | |
| AZT | C1 | 10 | 0 | 0 |
| C2 | 9 | 0 | 1 | |
| C4 | 9 | 0 | 0 | |
| S8 | 9 | 1 (1) | 1 | |
| POD | C1 | 10 | 0 | 0 |
| C2 | 9 | 0 | 0 | |
| C4 | 8 | 0 | 0 | |
| S8 | 9 | 1 (1) | 6 (6) | |
a
See footnote b of Table 2.
b
C1, C2, and C4, 1, 2, and 4 μg of clavulanate per ml, respectively; S8, 8 μg of sulbactam per ml.
c
See footnote a of Table 2.
d
The number in parentheses indicates the number of strains for which the MIC of the test drug alone was ≥2 μg/ml, thus fulfilling current NCCLS screening criteria for ESBL production by E. coli and Klebsiella spp. If the criteria were extended to these organisms, these strains would therefore be false positives for ESBL production in the inhibitor-drug combination tests.