Making It Easier to Categorize Patients With SAB

Staphylococcus aureus bacteremia.

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Staphylococcus aureus bacteremia (SAB) is uniquely characterized by its capacity to involve metastatic infections in nearly every organ system in the body. Approximately 20% of patients with SAB die within 30 days of nfection, and thus it’s important to address the limitations of categorizing the disease, according to a results of a study recently published in Journal of Infection.

Currently, patients with SAB are put into 1 of 2 therapy durations based on whether they have complicated or uncomplicated disease. Patients are grouped into largely comparable groups by clinicians, but this approach neglects to consider SAB’s intrinsic heterogeneity, the authors noted. Risk factors for metastatic infection and confirmed metastatic infection are not differentiated in most scoring methods, they said.

Further, including predisposing host characteristics, features of bacteremia, and the clinical course key restrictions in the definition of complicated SAB causes issues because SAB increases the risk of metastatic infection but SAB cases are not metastatic infections.

“As a result, it is possible for patients at risk for metastatic infection but without its confirmed presence to be diagnosed with and treated presumptively for complicated SAB,” the authors wrote. “In addition, the current classification can discourage a precise clinical diagnosis, since SAB encompasses a much wider range of clinical manifestations than uncomplicated and complicated SAB. Explicitly defining patient characteristics and SAB diagnosis would allow a more personalized treatment including shorter durations of intravenous (IV) therapy and more convenient routes of administration.”

“Clinicians need a classification for SAB that directs the diagnostic work-up and individualizes antibiotic treatment. This framework can also be used to identify knowledge gaps for future research.”

The classification proposed in the study begins after the patients’ initial positive blood culture. Each patient with SAB would have an evaluation, including physical examination, echocardiography, and repeat blood cultures. The patients would then be classified as having a high or low risk of metastatic infection. Only patients identified as high risk for complications could then undergo a more extensive diagnostic work-up to find or exclude these specific complications.

The classification proposed in the study begins after the patients’ initial positive blood culture.

Meanwhile, patients identified with no risk factors present at baseline or with negative results from the initial work-up would be noted as “low-risk SAB” would not receive the more extensive diagnostic work-up. “Ideally, the result of the more in-depth diagnostic work-up would delineate the extent and nature of the patient’s S aureus infection. This ‘final clinical diagnosis,’ and not a designation of complicated SAB solely on the basis of the presence of factors that are associated with metastatic infections, would correspond with a certain treatment strategy for the average patients with this clinical picture, including route of administration, duration, and load reduction,” the authors explained.

The last step, the authors noted, was “to establish the final treatment plan for the individual patient by further streamlining or changing the duration of the treatment based on clinical factors.” The investigators note, however, “for this classification to work in clinical decision-making, it must be able to accurately identify the absence of metastatic infections in patients with SAB, even when traditional evaluations fail to identify one.”

The classification of patients with SAB proposed in the study has the potential to resolve the inadequacies of only identifying uncomplicated and complicated SAB. This format consists of 4 steps. The first step is risk stratification for the presence of metastatic infection. If positive, then the clinician is directed to do a diagnostic work-up to find the infection. The “final clinical diagnosis” is determined with a general direction for treatment. And finally, treatment can be individualized for the patient. Also, “this framework guides the clinician and a context for future research to improve patient outcome and individualized treatment,” the authors noted.

REFERENCE

Kouijzer IJE, Fowler VG, Ten Oever J. Redefining Staphylococcus aureus bacteremia: a structured approach guiding diagnostic and therapeutic management. J Infect. 2023;86(1):9-13. doi:10.1016/j.jinf.2022.10.042