General notes: Blood is normally sterile and the presence of bacteria in the bloodstream (bacteraemia/septicaema) is a serious & potentially life-threatening condition. As even very small numbers of bacteria in the blood can cause severe illness, enough blood must be sampled to give the lab a chance of detecting them. Similarly, the techniques used to detect bacteria in blood are designed to pick up tiny numbers. This means that unless the samples are taken with great care & flawless aseptic technique, contaminants from the skin of patients or staff, cannulae or environment may be inoculated with the blood and give a positive result on culture.
It is often very difficult to distinguish contaminating bacteria from real pathogens and, in the best interests of the patient, each positive blood culture has to be telephoned to the relevant clinical team, by a microbiology registrar or consultant in order to assess the clinical implications. Often, patients have to be given antibiotics as a precaution, while a full identification of the bacterium is carried out.
