TABLE 3.

MtrD mutations eliminate the contribution of mtr and penB, but not that of penA, to penicillin and nafcillin resistancea

StrainmtrRmtrDpenMIC (μg/ml)
TETERYPENNAFTX-100
FA19++0.250.250.0150.25250
WV30 mtrR171 +0.252.00.031.0>16,000
WV31 mtrR171 mtrD::kan0.250.060.0150.0315
WV32++ penA4 0.250.250.1254.0250
WV33+ mtrD::kan penA4 0.250.060.1250.2515
WV34 mtrR171 + penA4 0.252.00.2516>16,000
WV35 mtrR171 mtrD::kan penA4 0.250.060.1250.2515
WV36 mtrR171 + penA4, penB 1.02.01.032>16,000
WV37 mtrR171 mtrD::kan penA4, penB 0.250.060.060.2531
  • a All abbreviations are as described in Table 2, footnote a. MICs are representative values from at least three determinations. +, wild type; −, no mutation in pen genes (see Table 1, footnote a).