1121. Public health importance of methicillin-sensitive Staphylococcus aureus (MSSA): results from pilot surveillance in five counties, 2014–2015
Session: Poster Abstract Session: MRSA/VRE Epidemiology
Friday, October 9, 2015
Room: Poster Hall
Background: Strategies for preventing Staphylococcus aureus infections have focused primarily on methicillin-resistant S. aureus (MRSA) rather than methicillin-sensitive S. aureus (MSSA).  We conducted a pilot of public health surveillance for invasive MSSA infections to describe the public health impact of MSSA and whether populations at risk for MSSA vs MRSA differed.

Methods: Active, population-based and laboratory-based surveillance was performed for invasive MRSA and MSSA in 5 counties from 4 states for 3–6 months during 2014–2015 (surveillance population: 4.0 million).  A case was isolation of MRSA or MSSA from a normally sterile body site in a surveillance area resident.  Cases were healthcare-associated if occurring on day ≥4 of hospitalization or in a patient with ≥1 healthcare exposure risk factors (hospitalization, long-term care facility [LTCF] residence, surgery, or dialysis in the prior year; or central venous catheter within 2 days prior).  Descriptive analyses were performed and multivariate logistic regression used to obtain adjusted odds ratios (aORs) and confidence intervals (CIs) for independent factors more associated with MRSA than MSSA.

Results: Complete case reports were obtained for 855 invasive S. aureus cases: 329 (38.5%) MRSA and 526 (61.5%) MSSA.  The % MRSA varied across sites (range: 34%–52%).  The site with the lowest %MRSA had the highest invasive S. aureus incidence (range: 23.1–49.2 cases/100,000 persons).  Most healthcare-associated cases (56.8%) and in-hospital deaths (55.1%) were from MSSA.  Patients with MSSA also tended to be younger (median age: 58 [MSSA] vs 63 years [MRSA], P=0.002) and healthier (16.7% [MSSA] vs 7.6% [MRSA] without underlying medical conditions, P=0.0001).  In multivariable analysis of patient and healthcare risk factors, female gender (aOR 1.40, 95% CI, 1.04–1.89), chronic pulmonary disease (aOR 1.47, 95% CI, 1.02–2.13), decubitus ulcer (aOR 2.81, 95% CI, 1.43–5.52), intravenous drug abuse (aOR 1.81, 95% CI, 1.08–3.03) and prior LTCF residence (aOR 3.81, 95% CI, 2.56–5.69) were associated with MRSA.  Notably, 65.3% of cases in previous LTCF residents were MRSA versus 34.1% in other patients (P<0.0001).

Conclusion: Strategies for preventing MSSA infections are needed to reduce the burden of healthcare-associated infections and deaths from S. aureus.  MRSA-specific prevention efforts appear to be particularly needed in LTCFs.

Isaac See, MD1, Nicole Gualandi, RN, MS/MPH1, Ghinwa Dumyati, MD, FSHEA2, Mackenzie Koeck, MPH3, Ruth Lynfield, MD, FIDSA3, Lauren Pasutti, MPH4, William Schaffner, MD, FIDSA, FSHEA5, Dwayne Wright, MD2 and Shelley S. Magill, MD, PhD1, (1)Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA, (2)University of Rochester Medical Center, Rochester, NY, (3)Minnesota Department of Health, St. Paul, MN, (4)California Emerging Infections Program, Oakland, CA, (5)Department of Health Policy, Vanderbilt University School of Medicine, Nashville, TN

Disclosures:

I. See, None

N. Gualandi, None

G. Dumyati, None

M. Koeck, None

R. Lynfield, None

L. Pasutti, None

W. Schaffner, None

D. Wright, None

S. S. Magill, None

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