Background Currently it can take up to 5 days to rule out bloodstream infection. With the low yield of blood cultures (approximately 10%), a significant number of patients are potentially exposed to inappropriate therapy that can lead to adverse events. More rapid rule out can accelerate deescalation or cessation of antimicrobial therapy, improving patient outcomes. Methods A method is described, termed enzymatic template generation and amplification (ETGA), that universally and sensitively detects DNA polymerase activity liberated from viable bacteria and fungi isolated from blood culture samples as a measure of bloodstream infection. ETGA was applied in a diagnostic test format to identify negative blood cultures after an overnight incubation. Performance data for a prototype (Cognitor) and automated (Magnitor) version of the test are presented. Results The Cognitor manual assay displayed analytical reactivity for a panel of the 20 most prevalent causes of bloodstream infection, with a detection range of 28–9050 CFU/mL. Validation with 1457 clinical blood cultures showed a negative predictive value of 99.0% compared to blood culture incubation for 5 days. Magnitor showed an improved detection range of 1–67 CFU/mL, allowing for detection of bacteria-supplemented blood cultures after 2–8 h incubation, and Candida albicans-supplemented blood cultures at 16–22 h, 5–15 h faster than blood culture. Removing an aliquot from a blood culture bottle and replacing the bottle into the incubator was shown not to result in contaminating organisms being introduced. Conclusions The described method displays excellent breadth and detection for microbial cells and demonstrates the capability of confirming negative blood cultures after an overnight incubation in a blood culture instrument.

Background Diagnosis of bloodstream infections (BSI) and treatment with appropriate antimicrobials is dependent upon fast and accurate information about the microorganism(s). The long time taken for a blood culture result, microbial identification and antimicrobial susceptibility testing (AST), can lead to poor antimicrobial stewardship. Many antimicrobial change decisions are based on the results of a Gram stain, with this being the first result available. Having results from a rapid test, direct from blood, which can confirm BSI and characterize the causative pathogen(s) would provide an improvement in antimicrobial stewardship and patient care. Methods SepsiSTAT® is a rapid molecular test, developed by Momentum Bioscience Ltd, for the detection of BSI, with a time-to-result of < 4 hours. It uses whole blood to detect viable microorganisms whilst also providing molecular characterization. Microorganisms are extracted from the sample using a proprietary process involving capture on magnetic microbeads. This is followed by Enzymatic Template Generation and Amplification (ETGA®) for ultra-sensitive, universal detection of viable bacterial and fungal species, based on detecting microbial DNA polymerase activity. Simultaneously, molecular characterization also provides genus/species identification. The detection limits of SepsiSTAT® were evaluated for a broad panel of microorganisms, representing 80% of BSI reported to Public Health England (2018 report). Results These results show a median detection limit (n=5) of < 10 cfu/mL in blood for microorganisms representing 77.4% of reported BSI, including key organisms such as E. coli, S. epidermidis and C. albicans. Notably, S. aureus, P. aeruginosa, E. faecalis, P. mirabilis and S. marcescens were all detected at < 1 cfu/mL. Conclusion SepsiSTAT® can detect microbes in low numbers, with a turnaround time substantially faster than traditional blood culture. Future development will aim to shorten time-to-results to < 3 hours, further benefiting patient outcomes and antimicrobial stewardship. Future studies in a clinical setting will seek to further demonstrate the efficacy and rapid turnaround time of the SepsiSTAT® test. Disclosures All Authors: No reported disclosures