Bacterial Infection Diagnosis Using Blood DNA

Sepsis is a common cause of morbidity and death in intensive care units. Clinical and laboratory signs of systemic inflammation, including changes in body temperature, tachycardia, or leukocytosis, are neither sensitive nor specific enough for the diagnosis of sepsis. The diagnosis of sepsis is difficult, because clinical signs are unspecific. These signs include tachycardia, leucocytosis, tachypnoea, and pyrexia, which are collectively termed a systemic inflammatory response syndrome (SIRS). SIRS is very common in critically ill patients, being found in various conditions including trauma, surgery, burns, pancreatitis, post-cardiac arrest syndrome, cardiac surgery. Microbiological culture can be used to distinguish sepsis from non-infectious conditions. However, this method lacks sensitivity and specificity, and there is often a substantial time delay. So these signs can also be misleading because critically ill patients often present with the systemic inflammatory response syndrome without infection. This issue is of paramount importance, since therapy and outcome differ greatly between patients with and those without sepsis; clinicians are often prone to overuse antibiotic therapy being afraid of not treating a potential infection or superinfection. Moreover, the widespread use of antibiotics for all such patients is likely to increase antibiotic resistance, toxicity, and costs. On the opposite, any delay in administration of antibiotics can be extremely detrimental for the infected patient with an exponential increase of the odd ratio for death. Search for early biomarker tools for the diagnosis of infection, initially promising, are quite challenged and controversial nowadays because they can be more related to the inflammation response, irrespective to the insult. Furthermore up to 40% of the infections remain strongly suspected but not bacteriologically documented. Persisting researches are ongoing to find new markers to better discriminate SIRS related to infection process from to SIRS not related to infection. Cytokine profiles using multiplex analysis seems more related to the severity of the SIRS than the trigger of the SIRS (infectious or non infectious diseases). Thus, new tools have been developed to identify bacteria by detecting their DNA by various techniques. These techniques have many potential interests over conventional microbiologic tests by decreasing turnaround time (within a few hours 2-6 hours), reducing inhibitory effects of prior use of antibiotics, detection of slow or fastidious growing organisms. However these tests remain to be validated in a clinical setting.

The goal of the current study is to evaluate the diagnostic value of plasma detection of bacterial DNA in ICU patients with a clinical suspicion of bacterial infection.