Sensitivity for S aureus based on vancomycin MIC is as follows: ≤ 2 mcg / mL (≤ 1.4 micromol / L): Sensitive 4 to 8 mcg / mL (2.8 to 5.5 micromol / L): Intermediate > 8 mcg / mL (> 5.5 micromol / L): Resistant However, infections due to S aureus with a vancomycin MIC ≥ 2 mcg / mL (≥ 1.4 micromol / L) may respond suboptimally to standard dosing even when the daily AUC is 400 to 600, so the threshold for changing to an alternative therapy should be low for patients with poor clinical response and an MIC of ≥ 2.