Molecular diagnosis of bloodstream infections with a new dual-priming oligonucleotide-based multiplex PCR assay

Mortality from bloodstream infections (BSIs) correlates with diagnostic delay and the use of inappropriate empirical treatment. Early PCR-based diagnosis could decrease inappropriate treatment, improving patient outcome. The aim of the present study was to assess the clinical utility of this molecular technology to diagnose BSIs. We assessed a new dual-priming oligonucleotide-based multiplex PCR assay, the Magicplex Sepsis Test (MST) (Seegene), along with blood culture (BC). A total of 267 patients from the intensive care unit and haematology and emergency departments were enrolled. Clinical data were also used by physicians to determine the likelihood of infection. Ninety-eight (37%) specimens were positive: 29 (11%) by both the MST and BC, 29 (11%) by the MST only, and 40 (15%) by BC only. The proportion of agreement between the two methods was 73% (Cohen's kappa: 0.45; 0.28-0.6; indicating fair to moderate agreement). According to clinical assessment, 63 (64%) positive specimens were considered BSIs: 23 (36%) were positive by both the MST and BC, 22 (35%) were positive only by BC, and 18 (29%) were positive only by the MST. Thirty-eight (14%) positive specimens by the MST and/or BC were considered as contaminants. Of 101 specimens collected from patients receiving antibiotics, 20 (20%) were positive by the MST and 32 (32%) by BC. Sensitivity and specificity were 65% and 92%, respectively, for the MST and 71% and 88%, respectively for BC. We concluded that the MST shows a high specificity but changes in design are needed to increase bacteraemia detection. For viability in clinical laboratories, technical improvements are also required to further automate the process.