Date Published: March 5, 2019
Publisher: Public Library of Science
Author(s): Catherine G. Sutcliffe, Lindsay R. Grant, Angelina Reid, Grace K. Douglass, Robert C. Weatherholtz, Robin Hubler, Alvaro Quintana, Raymond Reid, Del Yazzie, Mathuram Santosham, Katherine L. O’Brien, Laura L. Hammitt, Herminia de Lencastre.
Native Americans in the southwestern United States have a higher risk for many infectious diseases and may be at higher risk for Staphylococcus aureus due to the high prevalence of risk factors for S. aureus. Recent data on invasive S. aureus infections among Native Americans are limited.
Active population- and laboratory-based surveillance was conducted in 2016–2017 on the Navajo Nation to document the rate of invasive S. aureus. A case of invasive S.aureus infection was defined as a Native American individual with S. aureus isolated from a normally sterile body site whose reported community of residence was on or around the Navajo Nation.
One hundred and fifty-nine cases of invasive S. aureus from 152 individuals were identified. The median age of cases was 56.3 years and 35% were female. Thirty-five percent of cases had community-acquired infections. Ninety-three percent of cases had underlying medical conditions, including diabetes (60%) and obesity (42%), 28% of cases had a documented prior S. aureus infection, and 33% were infected with methicillin-resistant S. aureus. The annual incidence of invasive S. aureus and of invasive methicillin-resistant S. aureus was 64.9/100,000 persons and 21.2/100,000 persons, respectively.
This community has a high burden of invasive S. aureus infections. Further research is needed to identify prevention strategies and opportunities for intervention.
Staphylococcus aureus (SA) is a common cause of bacterial infections in the United States (US), causing non-invasive skin and soft tissue infections as well as invasive infections, including sepsis, pneumonia and necrotizing fasciitis. SA, particularly methicillin-resistant SA (MRSA), is responsible for a large number of hospitalizations and healthcare costs and is associated with significant all-cause mortality each year in the US [1–3]. In 2011, there were an estimated 80,461 cases and 11,285 deaths due to invasive MRSA in the US . Historically, MRSA infections were acquired in healthcare settings, but the proportion of community-acquired infections attributable to MRSA increased in recent years .
From May 1, 2016 to April 30, 2017, 169 isolates of invasive SA were identified. They were contributed by 159 cases of invasive SA from 152 individuals (5 individuals had 1 recurrent infection; 1 individual had 2 recurrent infections during the study period).
This study, which provides the first population- and laboratory-based estimates of invasive SA disease for the Navajo Nation, demonstrates a high burden of disease in this community. Most disease occurred among older adults and individuals with underlying medical conditions. Prior SA infections were reported for a quarter of cases, and recurrent infections were detected for four individuals in the 12-month study period, suggesting that exposure to SA in this community is common.
The burden of invasive SA was high with cases occurring predominantly among older adults with underlying medical conditions. The incidence of invasive MRSA on Navajo Nation was higher than the general US population. This has important implications for prevention strategies, treatment algorithms, healthcare utilization and expenditure planning. Continued surveillance is necessary to establish trends in the incidence of invasive SA and MRSA disease over time. Additional research priorities include establishing community colonization prevalence and identifying risk factors for both colonization and invasive disease to guide prevention strategies.