TABLE 2.
Total number of clones when testing concentrations above the MIC
| Antibiotic (Ab) | Ab concentration MICa | No. clones MICb | No. clones 2× MICb | No. clones 4× MICb | No. clones 8× MICb |
|---|---|---|---|---|---|
| Penicillin | 64 | 16 | 8 | 0 | 0 |
| Ampicillin | 8 | 50 | 9 | 5 | 0 |
| Cephalothin | 32 | 15 | 4 | 2 | 0 |
| Cefoxitin | 64 | 0 | |||
| Cefotaxime | 0.25 | 67 | 1 | 0 | 0 |
| Cefepime | 0.125 | 45 | 0 | 0 | 0 |
| Aztreonam | 0.25 | 19 | 3 | 0 | 0 |
| d-cycloserine | 32 | 24 | 0 | 0 | 0 |
| Polymyxin B | 0.5 | >1,000 | 0 | 0 | 0 |
| Chloramphenicol | 8 | 16 | 0 | 0 | 0 |
| Gentamicin | 4 | 0 | |||
| Amikacin | 16 | 0 | |||
| Tetracycline | 4 | 0 | |||
| Chlortetracycline | 4 | 0 | |||
| Doxycycline | 4 | 0 | |||
| Nalidixic acid | 4 | 0 | |||
| Norfloxacin | 0.125 | 0 | |||
| Nitrofurantoin | 1 | 0 |
a
The minimum concentration of antibiotic (μg/ml) needed to inhibit the growth of E. cloni cells (Lucigen). This concentration (MIC) was used to screen clones for cryptic antibiotic resistance.
b
The number of clones indicates the number of colonies that appeared if transformants showed resistance at the MIC, 2× the MIC, 4× the MIC, and 8× the MIC.