Unique Characteristics

The unique characteristics of the military-related study group prompted the authors to raise questions about its applicability across the general population.

One issue noted was the special situation of active-duty servicemembers, who are generally young, healthy, have open access to healthcare, yet have increased risk of SSTIs due to military training and related exposures. In fact, the study found that the rates of SSTIs and both bacteremia and SSTIs due to MRSA were higher in active duty personnel than others in the study group.

Because of the makeup of the TRICARE population, non-active-duty beneficiaries made up about 85% of the patients studied. Rates of bacteremia and SSTIs declined in both active-duty and non-active-duty groups, however, and the authors note that, “while the overall rates of disease were likely influenced by the characteristics of the Department of Defense population, the observed trends were consistent with investigations in other U.S. populations.”

Another way this study differed from previous research was the diverse locations of MTFs – urban, suburban and rural. In addition, TRICARE beneficiaries, because of the typically younger age of servicemembers and their families, tend to have lower rates of comorbid medical conditions, which are associated with increased S aureus bacteremia risk. Other large studies have tended to be conducted at urban tertiary-care centers, where many patients may have chronic kidney disease requiring hemodialysis and/or intravenous drug use.

In addition, most TRICARE beneficiaries have ready access to healthcare services and a reliable income, either while on active duty or following retirement, the study points out, explaining, “such factors may mitigate socioeconomic differences that have been associated with increased risk of MRSA infections.”

An advantage to looking at this population, however, was the ability to look at hospital-onset and community- infections simultaneously, according to the authors.

“The lines between the hospital and community settings have become less distinct in recent years,” they write. “Whether the changes in S aureus epidemiology, overall, were driven by changes within either the hospital or community settings, or both, remains uncertain. Improved infection-control practices may be affecting rates of both hospital-onset and healthcare-acquired community-onset MRSA bacteremia.”

Despite the positive trends, background information in the article notes that SSTIs have become a significant issue for the military. It states that, during training, 4% to 6% of troops deal with skin and soft-tissue infections and that S aureus has been isolated from 91% of such cases, with MRSA accounting for 70% of S aureus isolates.

Because of that and other resistant infection threats, the authors caution that vigilance on prevention and treatment needs to continue.

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1: Landrum ML, Neumann C, Cook C, Chukwuma U, Ellis MW, Hospenthal DR, Murray CK. Epidemiology of Staphylococcus aureus blood and skin and soft tissue infections in the US military health system, 2005-2010. JAMA. 2012 Jul 4;308(1):50-9. PubMed PMID: 22760291.