The immune response can acquire different profiles (proinflammatory and anti-inflammatory response) depending on the activating agent.The objective of this study is to compare the immunological profile in patients with severe sepsis and positive blood cultures.

Sepsis is one of the leading causes of death in patients admitted to intensive care. It is characterized by being an exaggerated and deregulated inflammatory response triggered by an infection. Although inflammation affects the compartmentalization of the infection, the activation of the immune system in sepsis has a systemic problem, which sometimes affects the organs distant from the site of infection. Within this context, two processes are recognized, which can often coexist: the pro-inflammatory response and the anti-inflammatory response. While it is assumed that the proinflammatory response may favor the development of multiple organ failure, sepsis-induced immunosuppression would favor a new infection, especially of endogenous and intranosocomial germs, mortality increases. The pro-anti-inflammatory nature of sepsis (if so can be defined) depends on a multitude of factors: the type of infection, personal history, genetic conditions, associated diseases, environmental factors, the use of immunosuppressive medications and nutrition. state, among others. Recent studies found that the immune response profile differs depending on the type of infection (Gram negative or Gram positive). Defining the predominant immune condition is not a simple task. Here there are no commonly used clinical variables that define the immune status, except for neutrophil counts.

Objetive:

• Define whether there are differences in the immunological profile between patients with sepsis and positive blood cultures by Gram negative and Gram positive.
• Identify easily accessible clinical and / or laboratory patterns that can predict the predominant immune character.

Design: The study was approved by the Scientific and Ethics committee of the institution. Informed consent will be requested.

Patients with severe sepsis and positive blood cultures will be included prospectively, within 24 hours of diagnosis of sepsis.

Consider severe sepsis to life-threatening organic dysfunction caused by a deregulated host response to infection. This concept includes at least a score of the SOFA (sequential evaluation of organic insufficiency) scale equal to or greater than 2 points The presence of one or more positive samples will be considered positive blood cultures.

Patients with severe sepsis will be enrolled prospectively and consecutively. Some of the blood used for blood culture samples will be processed for the study (sample 0). The plasma will be stored at -80 ° for later analysis. A routine clinical and laboratory database will be completed.

Only patients who have positive blood cultures will be randomized according to their result in: sepsis by Gram positive or Gram negative.

Patients with severe sepsis but with negative blood cultures will be considered a control group. In patients with positive blood cultures, new blood samples will be taken between days 3 to 5 of sample 0 to define the evolution of the pro and anti-inflammatory response.

Minimum 12 patients per group will be included. The level of proinflammatory cytokines (TNF alpha and IL 1) and anti-inflammatory (IL10 and IL1 receptor) will be measured by ELISA method. Finally, the data will be analyzed and the differences between patients with Gram-positive and Gram-negative infections will be established.

Primary Outcome Measure:

Measurement of the pro-inflammatory and anti-inflammatory response in patients with severe sepsis and positive blood cultures

Inclusion Criteria: severe sepsis -

Exclusion Criteria:

VIH immunosuppression Autoimmune disease Neoplasm Pregnant women Cirrhosis Bone Marrow Disease Malnutrition.

-

Patients with severe sepsis and positive blood cultures will be included prospectively, within 24 hours of diagnosis of sepsis.