Decreasing incidence of Staphylococcus aureus bacteremia over 9 years: Greatest decline in community-associated methicillin-susceptible and hospital-acquired methicillin-resistant isolates

摘要

Background: The impact of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) emergence on the epidemiology of S aureus bacteremia (SAB) is not well documented. Methods: This was an observational study of adult (aged ??18 years) inpatients with SAB in a single 808-bed teaching hospital during 2002-2003, 2005-2006, 2008-2009, and 2010 with period-stratified SAB rate, onset mode, patient characteristics, and outcome. Results: We encountered a total of 1,098 cases over the entire study period. The rate decreased steadily over time (from 6.64/103 discharges in 2002-2003 to 6.49/103 in 2005-2006, 5.24/103 in 2008-2009, and 5.00/103 in 2010; P =.0001), with a greater decline in community-associated cases (0.99/103, 0.77/103, 0.58/103, and 0.40/103, respectively; P =.0005) compared with health care-associated cases (5.65/103, 5.72/103, 4.66/103, and 4.60/103, respectively; P =.005). The decline was principally in MSSA (3.11/103, 2.21/103, 2.24/103, and 1.75/103, respectively; P =.00006), including both community-associated (P = .0002) and health care-associated cases (P =.006). Although overall rate changes in MRSA were not significant (P =.09), hospital-onset MRSA decreased markedly (P .00001), whereas CA-MRSA increased (P =.03). The all-cause 100-day mortality rate did not change significantly (25.6% for 2002-2003, 25.2% for 2005-2006, 28.1% for 2008-2009, and 32.2% for 2010; P =.10). Differences in MSSA/MRSA-associated mortality decreased (20.1% vs 30.6%, P =.03 for 2002-2003; 18.1% vs 28.9%, P =.05 for 2005-2006; 21.7% vs 32.9%, P =.05 for 2008-2009; and 29.3% vs 34.9, P =.5 for 2010). Conclusions: SAB incidence is decreasing, with the greatest decline in community-associated MSSA and hospital-onset MRSA cases. Most health care-associated cases currently are community-onset. MRSA/MSSA-related mortality is comparable. These changes are likely related to the emergence of CA-MRSA and the inpatient-to-outpatient shift in health care. ? 2013 by the Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.