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Bloodstream infection is a life-threatening condition with a high mortality rate, especially in intensive care and neutropenic patients. Standard diagnostics is based on blood culturing (BC). However, limitations of BC include relatively low sensitivities and a long time-to-result for the identification of the pathogen, generally over 2 days and more. On the grounds of data from a multicentre study using a universal 16S rRNA gene PCR assay, SepsiTest™, molecular diagnosis is discussed as a rapid and sensitive tool for the detection and identification of pathogens supportive of BC. A new commercial PCR test, SepsiTest™, for direct detection of bacteria in whole blood was compared with BC in terms of sensitivity, specificity, predictive values and time to positivity (TTP) of bacterial infections of the bloodstream of critically ill patients.
The test, SepsiTest™ (Molzym, Bremen), comprises the extraction and 16S rRNA gene PCR detection of bacterial DNA in whole blood samples. Bacteria in positive samples were identified by sequence analysis of the amplicon. In a prospective multicentre study, 342 blood samples from 187 patients with systemic inflammatory response syndrome (SIRS), sepsis, or neutropenic fever were included.
Compared with BC, the diagnostic sensitivity and specificity of PCR/sequencing was 87.0% and 85.8%, respectively. The positivity rate of PCR/sequencing (25.7%) was higher than BC (15.8%). Of 31 PCR/sequencing-positive, BC-negative patients, most of whom received antibiotics, the PCR results of 25 were judged as true or possible to bacteraemia. Using a routine testing workflow, time to positivity of the PCR test was on average decreased by 40 hours for anaerobe/fastidious infections and by 54 hours for yeast infections.
The PCR approach enables the detection and identification of bacteraemia in blood samples within a few hours. Despite the indispensability of BC diagnostics, the rapid detection of bacteria by SepsiTest™ appears to be a valuable tool, allowing earlier pathogen-adapted antimicrobial therapy in critically ill patients.