An infection of the blood that is circulated around the body.
Blood is normally a sterile environment. Microbes from other parts of the body or the external environment can gain access to and multiply within the blood. Bloodstream infections can be life-threatening.
An immune response to bacteria in the bloodstream can lead to sepsis, characterized by fever and low blood pressure, and, if untreated, multiple organ failure and death. Bloodstream infections are responsible for high levels of morbidity and mortality.
Many different types of microorganisms can establish bloodstream infections, and there is considerable variation in causative microorganisms in different parts of the world. Invasive medical procedures increase the risk of bloodstream infections, and so are common hospital-acquired infections. Bloodstream infections may be caused by drug-resistant microorganisms, and rising numbers of Gram-negative bacterial bloodstream infections are of great concern as these can be difficult to treat.