Hospital-acquired MRSA (HA-MRSA) per 1000 patient-days over time. Legend: X axis: years. Colonized patients are represented as dotted line and bacteremic patients as solid line. Left Y axis: number of HA-MRSA colonized patients per 1000 patient-days. Right Y axis: number of HA-MRSA bacteremic patients per 1000 patient-days. Chi2 test for trends: p < 10−7 for both colonized and bacteremic patients.