Table 2.
Minimal inhibitory concentrations of cefalotin and ceftazidime against Escherichia coli isolates.
| MIC of E. coli isolates (μg/mL) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Isolate | Antimicrobial | Parent type | -1 ∗ | -2 | -3 | -4 | -5 | -6 | -7 | -8 | -9 |
| E4 | Cefalotin† | 4 | 8 | 32 # | 80 # | 240 # | 240 # | 320 # | 320 # | 320 # | 320 # |
| Ceftazidime‡ | 0.125 | 0.25 | 2 | 4 | 16 # | 16 # | 32 # | 32 # | 64 # | 128 # | |
| E11 | Cefalotin | 0.5 | 2 | 16 | 32 # | # | # | # | # | # | # |
| Ceftazidime | 1 | 4 | 8 # | 8 # | 16 # | 32 # | 32 # | 64 | 128 # | 128 # | |
| E21 | Cefalotin | 2 | 8 | 16 | 16 | # | # | # | # | # | # |
| Ceftazidime | 0.5 | 1 | 4 | 4 | 8 # | 16 # | 16 # | 32 # | 32 # | 64 # | |
No mark: susceptible or intermediate to cefalotin or ceftazidime; #: resistant to cefalotin or ceftazidime. Breakpoints for cefalotin were as follows: susceptible ⩽ 8 μg/mL, intermediate 16 μg/mL, and resistant ⩾ 32 μg/mL. Breakpoints for ceftazidime were as follows: susceptible ⩽ 2 μg/mL, intermediate 4 μg/mL, and resistant ⩾ 8 μg/mL.
∗Escherichia coli isolates at various generations that were induced by cefalotin or ceftazidime.
†MIC values of cefalotin were determined for E. coli isolates induced by cefalotin.
‡MIC values of ceftazidime were determined for E. coli isolates induced by ceftazidime.