Validation of the sterilization procedure of allogeneic avital bone transplants using peracetic acid-ethanol

Different procedures are available to inactivate bacteria and fungi, including their spores, as well as viruses in human bone transplants. The most efficient methods are considered to be gamma irradiation and thermal inactivation as well as chemical sterilization methods like the peracetic acid-ethanol treatment (PES). Following national and international standards or draft standards, the antimicrobial effectiveness of this procedure was evaluated. Due to the standardizable size as well as the clinical relevance, defatted human spongiosa cuboids (15x15x15 mm) served as model system. After treatment with PES for 2 and 4 hours, respectively, the titre of living micro-organisms was determined in the supernatant and the cuboid. A reduction in the titre of viable micro-organisms below the detection level (reduction factor >5 log10) was already achieved after an incubation time of 2 hours (Staphylococcus aureus, Enterococcus faecium, Pseudomonas aeruginosa, Bacillus subtilis, Clostridium sporogenes, Mycobacterium terrae, Candida albicans as well as spores of Bacillus subtilis). No viable micro-organisms could be detected in any of the PES-treated test cuboids. Spores of Aspergillus niger were also completely inactivated. The PES procedure proved to be a reliable method for the sterilization of human bone transplants derived from spongiosa.