Bacterial skin flora and contamination of blood components: do we defer blood donors wisely?

Bacterial infection through contaminated blood is currently the greatest infection risk in relation to a transfusion. Deferral of prospective blood donors with a skin disorder is a common practise, because bacteria usually originate from the donor's skin. The effectiveness of current deferral guidelines to prevent the bacterial contamination of blood has not been assessed.

We recruited 55 blood donors with a skin disorder that prevented donation, and matched three controls for each case. The donors filled out a questionnaire and one bacterial culture sample was taken from venepuncture forearm skin.

The median total number of colony forming skin bacteria was significantly higher in the cases (224 CFUs per sample) than controls (105 CFU per sample). Staphylococcus aureus was significantly more often present on the skin in cases (49%) as compared to controls (7%). Regarding other bacterial genera, no difference between cases and controls was found.

This study shows that our current guidelines for deferral of blood donors with skin disorders effectively identifies individuals with a high number of bacteria on their skin, as well as S. aureus carriers. However, deferral due to skin disorders had only a minor impact on blood product contamination when compared to other actions.