[Microbial safety of blood products]

Septicemia caused by contaminated stored blood is a rare event, and the actual incidence is hard to determine due to a considerable variation of the different study protocols. This review is intended to give an overview of the pertinent literature considering causes, frequencies and kind of agents in contaminated blood products.

English and German literature as well as own data.

Original and review articles relevant to the topic.

The rate of septic episodes after transfusion of contaminated blood donations is approximately 0.3% (0.003-5%) of all blood transfusions. Contaminations of red cell preparations are predominantly caused by gram-negative bacteria, most often psychrophiles (Pseudomonas sp. Yersinia enterocolitica, Serratia). In platelet concentrates the prevailing bacterial organisms are represented by staphylococcal species. Bacterial contamination of blood and blood products may be generated in the process of blood collection and preparation of blood components. Materials and machinery used for blood processing may well serve as sources of contaminations. A considerable proportion of all contaminations must be attributed to transient, asymptomatic bacteremia of the donor. An additional predonation questionnaire addressing clinical symptoms associated with various pathological conditions (abdominal pain, tick-bites, malaria) has proven unpractical and may lead to a rejection rate of donors as high as 11%.

In-process bacteriological surveillance, stringent control of technical and hygienic conditions, and the use of leukocyte filters can reduce the risk of bacteria transmission. In case of transfusion reactions due to suspected bacterial contamination, blood samples of the patient as well as of the transfused blood product and the transfusion equipment used must be secure for microbiological examination.