Intermittent negative blood cultures in Staphylococcus aureus bacteremia; A retrospective study of 1071 episodes

Abstract

Abstract Background Recommended management of Staphylococcus aureus bacteremia (SAB) includes follow up blood culture sets (BCs) to determine the duration of bacteremia. Duration of bacteremia is an important prognostic factor in SAB and follow up BCs have a critical role in differentiation of uncomplicated and complicated SAB. However, intermittent negative BCs occur in SAB. Clinical guidelines for SAB management do not specify an approach to follow up BCs collection or define the number of negative BCs required to demonstrate resolution of bacteremia. This study assessed the frequency of intermittent negative BCs in SAB and used these finding to formulate a recommendation for collection of follow up BCs. Methods This retrospective study reviewed 1071 episodes of SAB. Clinical and microbiological data including the duration of bacteremia and the occurrence of intermittent negative BCs (those preceded and followed by positive cultures) were considered. Results Intermittent bacteremia occurred in 13% (140/1071) of episodes. A single negative BCs on days 1-3 had a predictive value of 87-93% for resolution of bacteremia although this was improved if all BCs collected within the same day were considered. Conclusions Intermittent negative BCs are common in SAB. Given this we would not recommend accepting a single negative BCs as demonstrating resolution of the bacteremia. This is particularly important if a patient is to be classified as having an uncomplicated SAB.