For this reason, blood cultures must be drawn with great attention to sterile process. The presence of certain bacteria in the blood culture, such as Staphylococcus aureus, Streptococcus pneumoniae, and Escherichia coli almost never represent a contamination of the sample. On the other hand, contamination may be more highly suspected if organisms like Staphylococcus epidermidis or Cutibacterium acnes grow in the blood culture.Two blood cultures drawn from separate sites of the body are often sufficient to diagnose bacteremia. Two out of two cultures growing the same type of bacteria usually represents a real bacteremia, particularly if the organism that grows is not a common contaminant. One out of two positive cultures will usually prompt a repeat set of blood cultures to be drawn to confirm whether a contaminant or a real bacteremia is present. The patients skin is typically cleaned with an alcohol-based product prior to drawing blood to prevent contamination. Blood cultures may be repeated at intervals to determine if persistent — rather than transient — bacteremia is present.Prior to drawing blood cultures, a thorough patient history should be taken with particular regard to presence of both fevers and chills, other focal signs of infection such as in the skin or soft tissue, a state of immunosuppression, or any recent invasive procedures.Ultrasound of the heart is recommended in all those with bacteremia due to Staphylococcus aureus to rule out infectious endocarditis. Definition
Bacteremia is the presence of bacteria in the bloodstream that are alive and capable of reproducing. It is a type of bloodstream infection.
Bacteremia is defined as either a primary or secondary process. In primary bacteremia, bacteria have been directly introduced into the bloodstream. Injection drug use may lead to primary bacteremia. In the hospital setting, use of blood vessel catheters contaminated with bacteria may also lead to primary bacteremia. Secondary bacteremia occurs when bacteria have entered the body at another site, such as the cuts in the skin, or the mucous membranes of the lungs (respiratory tract), mouth or intestines (gastrointestinal tract), bladder (urinary tract), or genitals. Bacteria that have infected the body at these sites may then spread into the lymphatic system and gain access to the bloodstream, where further spread can occur.Bacteremia may also be defined by the timing of bacteria presence in the bloodstream: transient, intermittent, or persistent. In transient bacteremia, bacteria are present in the bloodstream for minutes to a few hours before being cleared from the body, and the result is typically harmless in healthy people. This can occur after manipulation of parts of the body normally colonized by bacteria, such as the mucosal surfaces of the mouth during tooth brushing, flossing, or dental procedures, or instrumentation of the bladder or colon. Intermittent bacteremia is characterized by periodic seeding of the same bacteria into the bloodstream by an existing infection elsewhere in the body, such as an abscess, pneumonia, or bone infection, followed by clearing of that bacteria from the bloodstream. This cycle will often repeat until the existing infection is successfully treated.