Noves tecnologies per al diagnòstic molecular de la sèpsia

Abstract

Sepsis is a systemic response of the organism to the invasion by microorganisms and/or their toxins in the blood, characterized by a variety of humoral and cellular changes. Several factors will influencethe clinical outcome of the patient, such as the characteristics of the microorganism (inoculum, virulence), immunocompetence of the host (pathology, genetic factors, etc.) and the time elapsed until the administration of antibiotic treatment and appropriate support. Due to increased life expectancy and more aggressive treatments and exploratory manipulations, the incidence of sepsis increases year after year. This syndrome has a high mortality, being the first cause of death in the Intensive Care Unit. Moreover, it has been shown that the mortality is higher in patients receiving inadequate antibiotic treatment. Therefore, obtaining a rapid microbiological diagnosis is crucial in order to decrease mortality. Currently, the reference method (gold standard) for the microbiological diagnosis of sepsis is blood culture. Its main limitation is the average of 15 hours of incubation needed to obtain a positive result, and another 24-48 hours are needed for the identification and the antimicrobial susceptibility testing, which may cause a delay in the implementation of an effective antibiotic therapy. Furthermore, in patients who are already under antibiotic treatment prior to the inoculation of the blood culture, the performance of conventional microbiological techniques is lower, which means that, in many cases, the etiological diagnosis cannot be obtained and, therefore, the sensitivity to antibiotics of the microorganism causing sepsis is not known. Although there are several molecular assays commercially available, only SeptiFAST (Roche, Mannheim, Germany) has been extensively evaluated in the hospital setting showing heterogeneous results and has not been widely implemented yet._x000D_ This thesis has evaluated the usefulness of the technology PCR/ESI-MS for the molecular diagnosis of sepsis. This technique is based on a broad spectrum PCR followed by mass spectrometry electrospray ionization and is able to identify bacteria and fungi from direct specimens in about 6 hours. During the evaluation of the first version of this technology (PLEX-ID) promising results were obtained but its sensitivity was moderate (43.5%) in comparison with the conventional diagnostic methods. On the other hand, this technology was able to detect up to 12 clinically significant microorganisms that were not isolated by blood culture. However, because of its suboptimal sensitivity, the technology was refurbished. The new version, named IRIDICA, presents, as a major change, the increase of the volume of blood analyzed up to 5 mL (in comparison with the 1.250 mL used for the PLEX-ID). With the new version, the technology achieved a sensitivity of 73.0% in comparison with conventional methods. Furthermore, IRIDICA detected up to 41 clinically significant microorganisms in patients with negative blood culture, most of whom had previously received antibiotic treatment._x000D_ This thesis explores the usefulness of this technique in different types of patients. We analyzed samples of patients from the Emergency Room and patients admitted to the Intensive Care Unit. In the latter group, IRIDICA showed a higher sensitivity (83.0%) in comparison with conventional methods. These results are concordant with a recently published multicentric study that evaluated this technique for the molecular diagnosis of sepsis in critically ill patients admitted to the Intensive Care Units from six European countries._x000D_ In conclusion, IRIDICA is a robust, rapid and reliable technology for the detection of microorganisms directly from whole blood. This technology would increase the number of microbiologically confirmed sepsis cases, even in the presence of antimicrobial treatment. The utilization of this system would provide an early identification of the microorganism causing sepsis, with an improved performance in critically ill patients. Therefore, IRIDICA would lead to a prompter administration of the antimicrobial treatment, thus improving the survival rate and patient management.

Date of Award	11 Dec 2015
Original language	Catalan
Awarding Institution	Germans Trias i Pujol University Hospital
Supervisor	Elisa Marto Català (Director), Vicente Ausina Ruiz (Director) & Montserrat Giménez Pérez (Director)