TABLE 1.

Results of susceptibility testing using various methodologies to determine the presence of the heterogeneous vancomycin-intermediate Staphylococcus aureus phenotype

Isolate	Vancomycin MIC, mg/L					Daptomycin MIC, mg/L
	VITEK2*,†	Standard Etest*,†	Macro Etest*,‡	GRD Etest*,‡	BMD§	Etest*,†	BMD¶
Surveillance	0.5	1	2	1.5	2	1.0	Not done
Following nine days of vancomycin therapy	1	1	3	1.5	2	1.0	1.0
Following 37 days of daptomycin therapy	4	3	8	6	4	≥4.0	> 4

^*bioMérieux Inc, USA;

^†VITEK2 and standard Etest for vancomycin and daptomycin were performed at the Hamilton Regional Laboratory Medicine Program, Hamilton, Ontario;

^‡Etest using 2.0 McFarland inoculum (Macro Etest) and the glycopeptide resistance determinant (GRD) Etest was performed at the National Microbiology Laboratory, Winnipeg, Manitoba;

^§Broth microdilution (BMD) testing performed at the Ontario Agency for Health Protection and Promotion, Central Public Health Laboratory, Toronto, Ontario;

^¶BMD testing performed at the Hamilton Regional Laboratory Medicine Program using Sensititre (TREK Diagnostics Inc, USA). MIC Minimum inhibitory concentration