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Decreasing Incidence of Staphylococcus Aureus Bacteremia Over 9 Years: Greatest Decline in Community-Associated Methicillin-Susceptible and Hospital-Acquired Methicillin-Resistant Isolates

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) in-patients 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 ¼ .0001), with a greater decline in community-associated cases (0.99/103, 0.77/103, 0.58/103, and 0.40/103, respectively; P ¼ .0005) compared with health care associated cases (5.65/103, 5.72/103, 4.66/103, and 4.60/103, respectively; P ¼ .005).  The decline was principally in MSSA (3.11/103,2.21/103, 2.24/103, and 1.75/103, respectively; P ¼ .00006), including both community-associated (P ¼ .0002) and health care associated cases (P ¼ .006).  Although overall rate changes in MRSA were not significant (P ¼ .09), hospital-onset MRSA decreased markedly (P < .00001), whereas CA-MRSA increased (P ¼ .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 ¼.10). Differences in MSSA/MRSA-associated mortality decreased (20.1% vs 30.6%, P ¼ .03 for 2002-2003; 18.1% vs 28.9%, P ¼ .05 for 2005-2006; 21.7% vs 32.9%, P ¼ .05 for 2008-2009; and 29.3% vs 34.9, P ¼ .5 for 2010).

Conclusions: SAB incidence is decreasing, with the greatest decline in community-associated MSSA and hospital-onset MRSA cases.  Most healthcare 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.

Author: Khatib R, Sharma M, Iyer S, Fakih MG, Obeid KM, Venugopal A, Fishbain J, Johnson LB, Segireddy M, Jose J, Riederer K

Citation: American Journal of Infection Control 2013; 41:210-213. DOI: 10.1016/j.ajic.2012.03.038.

Published: 01/01/2013

Publication Type: Journal article

Publisher: American Journal of Infection Control