Currently, pathogens in blood of patients with potential blood stream infection are identified by microbiological methods with blood culture as gold standard. Since blood culture has several limitations such as long time to identify causative pathogens, inconclusive results due to antimicrobial treatment and insufficient detection of intracellular or slow growing pathogens, molecular diagnostics approaches have been developed. In particular, these approaches are based on polymerase chain reaction (PCR) providing a short time - to - result, compatibility with antimicrobial treatment and the absence of pre - selecting culture steps. Despite these advantages, PCR - based systems still may suffer from a reduction in sensitivity or inhibited results due to interfering matrix components requiring efficient pathogen enrichment and pre - analytical sample processing. Beyond that, pathogen DNA persisting in the circulation of patients after resolved infection may lead to false positive results.
To address limitations of molecular diagnosis of blood stream infection we will identify potential interfering factors by a retrospective analysis of a database from the Medical University Innsbruck containing over 2,000 samples analysed with a specific molecular procedure, including samples with inhibited PCR - results. Candidate factors will be further investigated by spiking them into different matrices. Furthermore, we will determine the persistence of pathogen DNA in the blood stream to distinguish between pathogen DNA residuals potentially exacerbating the course of infection and pathogens acquired from a new episode of infection requiring further antimicrobial treatment.
Additionally, it is of interest for us to identify potential markers for host response during blood stream infection as a high percentage of blood cultures from patients fulfilling clinical sepsis criteria remain negative. We will investigate the potential of increased numbers of extracellular vesicles, their coherence with C - reactive protein and complement proteins, or changes in extracellular vesicle glycosylation patterns as markers for blood stream infection.
This project should close existing gaps in pathogen detection with the aim to improve prospective diagnosis of patients suffering from blood stream infection with respect to accuracy as well as time - to - result.
