There are two major categories of bloodstream infections. They are;
- Intravascular: Those that originate within the cardiovascular systems. Examples include infective endocarditis, mycotic aneurysm, suppurative thrombophlebitis, and intravenous catheter-associated bacteremia.
- Extravascular: Those that result from bacteria entering the blood circulation through the lymphatic system from another site of infection. Organisms multiply at the local site of infections such as lungs and drained by the lymphatics into the bloodstream.
The most common portals of entry for bacteremia are the genitourinary tract (25%), respiratory tract (20%), abscesses (10%), surgical wound infections, biliary tract, and miscellaneous sites.
Microbial invasion of the bloodstream constitutes one of the most serious situations in infectious diseases. It can have serious immediate consequences such as shock, multiple organ failure, disseminated intravascular coagulation (DIC), and death.