Association of Hyperglycemia With Outcomes in Staphylococcus aureus Bacteremia in Community-Dwelling Adults

Abstract

Bacteremia due to Staphylococcus aureus is commonly seen in both healthcare-associated infections and in older adults.1,2 The mortality and morbidity associated with these infections continue to be high. In this issue, Bader3 reports an association of hyperglycemia with mortality and nonhome discharge in community-dwelling older adults with S. aureus bacteremia. The study of Bader3 is actually a reanalysis of data collected in 2003 to 2004 with application to community-dwelling adults only. This, however, is not a study of community-acquired or community-onset bacteremia because 37% of these patients had nosocomial bacteremia and 47% had an intravascular device. The source of bacteremia is a potentially important factor in assessing the probability of mortality. This was not defined by the author. The author chose to select patients for analysis whether they had S. aureus bacteremia with fever and an elevated white blood cell count, but elderly patients may have sepsis with bacteremia while lacking fever and/or leukocytosis. This may have resulted in some selection bias. Levels of hemoglobin A1c did not differ between those who did and did not survive. The hyperglycemia noted in these patients was more likely acute and secondary to the bacteremia and not a pre-existing or predisposing factor. The notion that hyperglycemia correlates with poor outcome in critically ill patients, including those with S. aureus bacteremia, is not new.4,5 Based on these observations, studies attempting to correlate tighter control of hyperglycemia with improved outcomes in Intensive Care Unit (ICU) patients have been conducted and published. No evidence of improved mortality with tighter control of hyperglycemia has been observed.6,7 Current recommendations for the management of hyperglycemia in critically ill patients reflect the lack of evidence-based support for tight control.8 Significant changes in the management of S. aureus bacteremia have occurred in the years since the completion of this study. Several important interventions have been recognized to result in improved mortality as follows: the timely use of appropriate therapy9; consultation by an infectious diseases specialist10; the possible use of alternative therapy in persistent or complicated cases11,12; the recognition that vancomycin is suboptimal in methicillin-susceptible S. aureus bacteremia and in methicillin-resistant S. aureus bacteremia with vancomycin minimal inhibitory concentrations of 2 μg/mL or higher13,14; the timely removal of intravascular devices15; and early heart valve surgery in infective endocarditis.16 In addition, the use of transesophageal echocardiography, the routine follow-up blood cultures to recognize complicated cases of S. aureus bacteremia, and the search for secondary foci of bacteremia have become routine.17 It is not possible to predict the outcomes of patients observed in this study if such interventions introduced in recent years had been applied in their care or whether the differences in patients with hyperglycemia would persist. Specifically, in the absence of follow-up blood culture data, it is impossible to distinguish the effect of persistent/complicated S. aureus bacteremia on hyperglycemia. In managing a patient with S. aureus bacteremia, the control of hyperglycemia is just one of many important considerations, and lacking evidence-based support from prospective studies, we cannot recommend tighter control of hyperglycemia than that recommended in current guidelines.8 Marked, persistent hyperglycemia during treatment of S. aureus bacteremia should be a warning to clinicians that all are not well and that additional diagnostic and therapeutic interventions may interrupt the progression to death or complications with a resulting discharge to a nonhome setting.