TABLE 2.

Insertional inactivation of MtrD eliminates the intermediate- and high-level chromosomally mediated penicillin resistance of strains FA140 and FA6140a

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
FA140 mtrR140 + penA2, penB2 1.02.01.08.0>16,000
WV24 mtrR140 mtrD::kan penA2, penB2 0.250.060.060.12531
FA6140 mtrR171 + penA4, penB, ponA1 4.02.04.032>16,000
WV22 mtrR171 mtrD::kan penA4, penB, ponA1 1.00.060.251.031
  • 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).