Detection of relevant pathogens and contaminants in blood cultures after implementation of single-sampling strategy and initial specimen diversion.

PURPOSE: Blood culture collection with all bottles filled from a single venipuncture (single-sampling strategy, SSS) is increasingly used. More data on the effects of SSS on blood culture contamination is needed. After combined implementation of SSS and initial specimen diversion (ISDT) in our region, we evaluated the proportion of sampling events with at least four bottles, with growth of relevant pathogens and with growth of coagulase-negative staphylococci (CoNS) before and after the intervention. METHODS: We retrospectively reviewed all blood cultures collected from adults in emergency departments in our region in southern Sweden during six years before and 18 months after the intervention. RESULTS: Among 117 142 sampling events included in the analysis, the proportion where at least four bottles were obtained increased from 87.6 to 92.3% (p < 0.001), while growth of relevant pathogens remained unchanged at 13.6%. In the subset of sampling events with no more than one species, there was a decrease in the proportion with CoNS in 1–2 out of 4 bottles (4.0 to 3.3%, p < 0.001), while events with CoNS in 3–4 out of 4 bottles increased (0.39 to 0.49%, p = 0.029). CONCLUSION: We confirm positive effects of SSS and ISDT on adequate sample volume and a net decrease in the proportion of sampling events with growth of CoNS. Conversely, we observed an increase in CoNS in multiple bottles, probably caused by contamination. This possible drawback with SSS has not been reported before and should be studied further.