Linear regression coefficients among vancomycin and daptomycin susceptibilities and cell wall thicknessesa

VariablebLinear regression coefficientc
Cell wall thickness (nm) (46d)DPT length (cm) (52)VCM length (cm) (52)VCM MICDPT MIC
BHI broth (53)MH broth (53)BHI broth (53)MH broth (53)
24 h48 h24 h48 h24 h48 h24 h48 h
Cell wall thickness (nm)0.8830.8620.8610.9030.8160.8290.6520.7820.6530.679
DPT length (cm)0.8140.7840.8110.7430.8020.5890.7140.5690.674
VCM length (cm)0.8920.8950.8080.8390.7150.8070.6440.634
VCM MIC, BHIb, 24 h0.9550.8990.9240.6760.7790.5760.605
VCM MIC, BHIb, 48 h0.8950.9210.7470.8140.6730.708
VCM MIC, MHb, 24 h0.8940.6860.7760.6240.658
VCM MIC, MHb, 48 h0.6810.7780.6310.699
DPT MIC, BHIb, 24 h0.9270.7740.733
DPT MIC, BHIb, 48 h0.7620.807
DPT MIC, MHb, 24 h0.829
DPT MIC, MHb, 48 h
  • a Linear regression analysis was performed on the values of vancomycin and daptomycin susceptibility and cell wall thickness. The susceptibility tests were performed with various culture conditions and methods (see the text). The values of cell wall thickness are from our previous report (9). P values are <0.0001 for all tests.

  • b Abbreviation: VCM, vancomycin; DPT, daptomycin; BHIb, brain heart infusion broth; MHb, Mueller-Hinton broth; MIC, minimum inhibitory concentration (mg/liter). DPT length, VCM length, etc., refer to length of bacterial growth on the antibiotic gradient gel. The MICs were read at 24 and 48 h of incubation.

  • c No. of tested samples is given parenthetically after each variable.

  • d For cell wall thickness and length of growth with DPT, no. of samples is 45.