Trends in Staphylococcus aureus Bloodstream Infections in Nursing Homes in Monroe County, New York

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSIs) are common in hospitals and nursing homes. Infection prevention efforts reduced MRSA BSI in hospitals but the trend in nursing homes is not well described. In addition, the contribution of methicillin sensitive S. aureus (MSSA) to the total burden of invasive S. aureus (iSA) in nursing homes remains unknown. Methods: As part of the CDC Emerging Infections Program, we conduct population-based surveillance for iSA infections in Monroe County, New York. Case patients were county residents with S. aureus isolated from a sterile site. Our analysis was limited to data from 2009–2018 for MRSA and 2015–2018 for MSSA and to cases classified as hospital-onset (HO, positive culture ≥3 calendar days after admission) or nursing home-onset (NHO, positive culture in nursing homes or within 3 days of hospital admission from a nursing home). Risk factors for iSA BSI in nursing homes were compared using the χ² and Student t tests in SAS version 9.4 software. Results: During 2009–2014, 664 MRSA cases occurred and 427 (64%) were BSIs. Of these, 228 (53%) were NHO and 199 (47%) were HO. The BSI incidence per 100,000 population of NHO cases declined from 7.9 in 2009 to 2.8 in 2014, mirroring the decline in HO incidence from 8.7 in 2009 to 3.1 in 2014 (Fig. 1). During 2015–2018, 203 MRSA cases (163 BSIs, 80%) and 235 MSSA cases (163 BSIs, 69%) occurred. Of the 163 MRSA BSIs, 94 (58%) were NHO and 69 (42%) were HO, whereas of the 235 MSSA BSIs, only 56 (34%) were NHO and 107 (66%) were HO. MRSA BSI incidence per 100,000 population in both settings plateaued during 2015–2018 (Fig. 1) and MSSA NHO BSI incidence was lower than HO (1.9 NHO vs 3.6 HO). The total iSA BSI incidence was similar in both settings (5.9 vs 5.0 per 100,000 population in HO and NHO, respectively). NHO MSSA and MRSA cases have similar risk factors for BSI; 45 (30%) had decubitus ulcers, 34 (23%) were on chronic dialysis, 41 (27%) had a CVC in place within 2 days of BSI onset, and 63% had prior healthcare exposures. Most of these developed within 4 weeks of hospital discharge (Fig. 2). Conclusions: The incidence of MRSA BSI in nursing homes has declined since 2009 but plateaued starting in 2015. Compared to MRSA, MSSA caused fewer BSIs in nursing homes; however, iSA risk factors, including previous healthcare exposure, were similar. Continued study is needed to identify interventions effective against all iSA infections in nursing homes.

Funding: None

Disclosures: None