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Center for Community Health & Prevention

Surveillance & Prevention

URMC / Center for Community Health & Prevention / Surveillance & Prevention / Emerging Infections Program / Invasive Staphylococcus aureus Surveillance

Invasive Staphylococcus aureus Surveillance

Purpose

To perform active population-based surveillance for invasive Staphylococcus aureus (iSA) infections in Monroe County, New York. 

Goals and Objectives

  • Invasive Staphylococcus aureus infectionMonitor changes in incidence and epidemiologic characteristics of invasive Methicillin-resistant S. aureus (MRSA) and invasive Methicillin-sensitive S. aureus (MSSA) infections in Monroe County, New York.
  • Classify infections into one of three epidemiologic classes: hospital-onset (HO), healthcare-associated community-onset (HACO), and community-associated (CA).
  • Describe the molecular epidemiologic patterns and microbiologic characteristics of iSA.

Activities

MRSA laboratory and population surveillance began in 2005 and was expanded in 2015 to include MSSA (collectively called iSA). An iSA case is defined as isolation of S. aureus from a normally sterile site in a Monroe County resident. Normally sterile sites include blood, bone, cerebrospinal fluid, joint fluid, pericardial fluid, peritoneal fluid, pleural fluid, muscle, or surgically obtained sterile fluid or deep tissue.

Cases are reviewed and classified into one of three epidemiologic subclasses defined below:

  • Hospital-onset (HO): If the S. aureus culture was obtained ≥3 days after hospitalization
  • Healthcare-associated community-onset (HACO): If the S. aureus culture was obtained in an outpatient setting or <3 days after hospitalization in a patient with ≥1 prior major healthcare exposures such as history of hospitalization, surgery, dialysis, or residence in a long-term care facility in the previous year
  • Community-associated (CA): If the S. aureus culture was obtained in an outpatient setting or <3 days after hospitalization in a patient with no documented prior major healthcare exposures. 

The figure below shows iSA incidence by year and S. aureus resistance type (MRSA or MSSA) with MSSA accounting for two third of cases. Despite infection prevention efforts focusing primarily on MRSA prevention, MSSA contributes significantly to the overall iSA burden. 

graph

The figure below shows the year-to-year changes in iSA rates by S. aureus resistance type and epidemiologic classification since 2019. In 2023, the incidence of HO-iSA and HACO-MRSA increased significantly since the 2019 baseline. Although HACO-MSSA and CA-iSA significantly increased from 2020 to 2021, their 2023 rates remained stable relative to 2019 rates.

change in rate graph

The Monroe County iSA data is combined with other EIP sites across the country; see the latest national trends here.

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