Table 3.

Effect of PBP4 overproduction on vancomycin susceptibility

Strain or isolateVancomycin MIC (μg/ml)a
Broth microdilutionbE-test
ParentParent + pJF3(pbp4)Parent + pRN5543ParentParent + pJF3(pbp4)Parent + pRN5543
RN450M222222
Mu3222323
Mu50636838
HIP58271231212412
HIP5836828868
HIP6297636636
  • a Microdilution MICs were determined at 1-μg/ml increments of vancomycin.

  • b In order to keep pressure on plasmid pJF3, 5 μg of chloramphenicol per ml was also added. Failure to do so resulted in loss of the plasmid.