Sepsis is a clinical syndrome with a whole-body inflammatory state, systemic inflammatory response syndrome (SIRS) in combination with a known or suspected infection. SIRS is characterized by at least two of the following signs and symptoms: unusually high or low white blood count, unusually high or low body temperature, high pulse, high respiratory rate, and low carbon dioxide pressure in the blood.

SIRS can occur without the presence of infection, as a result of e.g. burns, trauma, in the initial state of pancreatitis, or in chemical pneumonia. In sepsis, the inflammatory response is developed in by the immune systems towards microorganisms in the blood, urine, lungs, skin, or other tissues. Microorganisms in the blood may be the effect of an infection in a different site of the body, or related to the presence of a catheter.

Sepsis with complications of organ dysfunction, decreased blood flow (hypoperfusion), or low blood pressure (hypotension) is termed severe sepsis. Severe sepsis with hypotension that is not reversed by treatment with fluids, along with perfusion abnormalities, is termed septic shock. Septic shock may result in multiple organ dysfunction syndrome (MODS), a condition with altered function of multiple organs that cannot be restored without intervention.

Sepsis occurs in 1 -2 % of all hospitalizations and septic patients represent a significant part of intensive care unit bed utilization. Among septic populations, infection-related complications pose an increasing economic healthcare burden due to prolonged hospital stay and life-sustaining measures. A rough measure of mortality rates is 20 % for sepsis, 40 % for severe sepsis, 60 % for septic shock, and 80 % for MODS. In intensive care units, sepsis is the third most common cause of death after coronary heart disease and myocardial infarction.

A broad range of bacteria and fungi may be involved depending on the clinical condition. However, less than 30 bacteria and fungi are believed to produce more than 80% of the clinically relevant sepsis cases. Less than 50% of blood cultures of septic patients yield a positive result even when true bacterial or fungal sepsis is believed to exist.

Antimicrobial therapy is a key element in treatment of sepsis patients. In severe sepsis, there is a rapid fall in survival rate from around 80% in case of adequate antimicrobial therapy to less than 10% in case of inadequate therapy within the first 24 hours. Clinical diagnosis of sepsis can be challenging in adults and children. For instance, neonates may be relatively asymptomatic until hemodynamic and respiratory collapse is imminent. Thus, clinicians often resort to empirical antibiotic therapy if there is even a remote suspicion of sepsis until cultures are sufficiently proven to be negative since delayed diagnosis equals increased mortality and morbidity.

In clinical management antibiotic treatment is initiated along with other treatment, before the identity of the infectious agent is known. Samples are taken and sent to the microbiology lab for typing. Patients are monitored hourly. If patient status deteriorates, the patient may be transferred to intensive care and continuously monitored. When results from the lab on type of agent and later, species and antibiotic susceptibility information become available, treatment may be changed by administering a different antibiotic.

Antibiotics resistance 

Antibiotics are used to treat infections, by killing or inhibiting the growth of microorganisms. Some strains of microorganisms are resistant to certain antibiotics, due to the presence of resistance genes. In the presence of selective pressure, resistant strains will expand compared to non-resistant strains.

Resistance genes may also spread between species by so-called lateral gene transfer. It is believed that the extensive use of antibiotics in health care, food industry and veterinary medicine is a cause of the increasing prevalence of infections with resistant strains observed.

Resistant strains are a major health-care problem. Infections that would otherwise be trivial may be deadly if the causing agent is resistant to available drugs and treatment of neonatal and immunosuppressed patients (such as patients undergoing organ transplants or chemotherapy) are complicated by this fact.

When blood samples are sent to microbiology labs for culturing, cultures that are positive for bacteria (or funghi) are subjected to antibiotic susceptibility testing. If the infecting agent is resistant to an administered drug, the therapy can be changed to an effective antibiotic. Often, the response time for these tests is too long to affect treatment, and results may then be used to monitor resistance patterns and to update empirical antibiotic treatment guidelines (which antibiotics to use for different species).

The Nordic countries and the Netherlands have up to now been less affected by resistant infections, mainly due to more restrictive strategies on use of antibiotics. In the southern parts of Europe, e.g. Greece and Romania, resistant infections are widely spread.  It is very likely that the situation in the Nordic countries and the Netherlands over time will come to look like the situation in the rest of the EU.