How CDC Tracks Invasive Staph Infections

An invasive Staphylococcus aureus (S. aureus) infection is one found in a normally sterile part of the body. CDC's Invasive Staphylococcus aureus Infection Surveillance Program collects data on how often these infections happen and how that is changing, so that public health and health care professionals can research them and improve prevention.

The program is part of the Healthcare-Associated Infections – Community Interface (HAIC) activity of CDC's Emerging Infections Program (EIP).

What it monitors

• Changes in the incidence of invasive infections with both methicillin-resistant and methicillin-sensitive S. aureus (MRSA and MSSA), split by where they began:
• • hospital-onset (HO);
  • health care-associated community-onset (HACO);
  • community-associated (CA).
• Groups of patients who would benefit from better prevention and treatment.
• The impact of established prevention strategies.
• The molecular and microbiological traits of the strains causing infections.

How it works

Trained staff at 7 EIP sites run active, population- and laboratory-based surveillance: they regularly query clinical laboratories for test results among people living in defined areas. CDC and EIP staff clean and analyze the data and publish annual reports and peer-reviewed papers. The data can also be explored in CDC's Antimicrobial Resistance & Patient Safety Portal, which adds case rates and deaths over time.

A case is S. aureus isolated from a normally sterile site in a resident of a surveillance area — blood, cerebrospinal fluid, pleural, peritoneal or pericardial fluid, bone, joint (synovial) fluid, or an internal site such as a lymph node or the brain.

Where

In Connecticut and Georgia, MSSA is tracked in a smaller area than MRSA: the South Central Connecticut and Naugatuck Valley Planning Regions, and Fulton County.

What 2024 showed

• Invasive S. aureus infections were most often health care-associated community-onset.
• Compared with 2023, invasive MRSA rose in the community-associated and HACO categories, while hospital-onset MRSA fell slightly.
• Invasive MSSA fell in all three categories.

Annual reports are published for each year back to 2005; those through 2015 are MRSA reports.

Research using the data

Studies drawing on the program include work on MRSA bloodstream infection trends at six EIP sites from 2005 to 2022, nursing homes with high rates of invasive MRSA, health disparities in hemodialysis-associated S. aureus bloodstream infections in 2017–2020, the public health importance of invasive MSSA in 8 U.S. counties in 2016, and how MRSA bloodstream infection trends from 2005 to 2013 differed by strain type and health care exposure.

Sources

• Centers for Disease Control and Prevention: "Invasive Staphylococcus aureus Infection Surveillance."