Bacteremia is the presence of bacteria in the blood, and is the means by which local infections spread hematogenously to distant organs. It is typically transient rather than continuous, which is why blood cultures must be repeated at intervals to determine if bacteremia is or is not present.

Hematogenous dissemination of bacteria is part of the pathophysiology of meningitis and endocarditis, and of Pott's disease and many other forms of osteomyelitis. In the hospital, indwelling catheters are a frequent cause of bacteremia and the subsequent nosocomial infections, because they provide a means by which bacteria normally found on the skin can enter the bloodstream. Other causes of bacteremia include dental procedures, urinary tract infections, IV drug use, and colorectal cancer.

Bacteremia is operationally defined as the presence of viable bacteria as evidenced by positive blood cultures. Dental work is most commomly associated with bacteremia. Also seen in oropharyngeal , gastrointestinal or genitourinary surgery or exploration. Simple activities like eating and brushing can also lead to mild transient bacteremia.

When it occurs in the presence of systemic symptoms (such as fever or chills) the condition is deemed septicemia; and in the setting of more severe disturbances of temperature, respiration, heart rate or white blood cell count, is characterized as systemic inflammatory response syndrome (SIRS). Similar terms are sepsis, sepsis syndrome, septic shock, and multiple organ dysfunction syndrome.

See also: fungemia