TABLE 2.
Insertional inactivation of MtrD eliminates the intermediate- and high-level chromosomally mediated penicillin resistance of strains FA140 and FA6140a
| Strain | mtrR | mtrD | pen | MIC (μg/ml)
|
||||
|---|---|---|---|---|---|---|---|---|
| TET | ERY | PEN | NAF | TX-100 | ||||
| FA19 | + | + | − | 0.25 | 0.25 | 0.015 | 0.25 | 250 |
| WV30 | mtrR171 | + | − | 0.25 | 2.0 | 0.03 | 1.0 | >16,000 |
| WV31 | mtrR171 | mtrD::kan | − | 0.25 | 0.06 | 0.015 | 0.03 | 15 |
| FA140 | mtrR140 | + | penA2, penB2 | 1.0 | 2.0 | 1.0 | 8.0 | >16,000 |
| WV24 | mtrR140 | mtrD::kan | penA2, penB2 | 0.25 | 0.06 | 0.06 | 0.125 | 31 |
| FA6140 | mtrR171 | + | penA4, penB, ponA1 | 4.0 | 2.0 | 4.0 | 32 | >16,000 |
| WV22 | mtrR171 | mtrD::kan | penA4, penB, ponA1 | 1.0 | 0.06 | 0.25 | 1.0 | 31 |
a
MIC of TET (tetracycline), ERY (erythromycin), PEN (penicillin G), NAF (nafcillin), and TX-100 are representative values for three or more determinations. +, wild type; −, no mutation in pen genes (see Table 1, foonote a).