Abstract
Disease transmission and bacterial in fection in bone allograft transplantation is of significant concern. Screening of donor for d isease, bacterial testing and aseptic processing, substantially reduce risk, but do not co mpletely eliminate the possibility of allograft associated infections. Sterilization by gamma rad iation is a defin itive method for eliminating microorganis ms and can prevent life-threatening allograft associated infections. In the present study, microbiological evaluation of bone allografts processed fro m femo ral heads excised during surgery was carried out. 126 femo ral heads obtained from living donors were processed, freeze-dried and sterilized by gamma irradiation at 25 kGy . The bioburden and type of microbial contamination associated with bone allografts was determined based on morphological characteristics and biochemical tests. Resistance of bacterial contaminants to gamma radiat ion was evaluated by exposing the bacterial cell suspension to different doses of 1 to 6 kGy and analysing for the surviving bacteria. Average bioburden of p rocessed bone allografts for different batches was found to be in the range of 1.84 x 10 2 to 3.88 x 10 3 CFU/g. 60.2% o f the isolates were found to be Gra m-positive organis ms. The D10 value of bacterial isolates ranged fro m 0.56 to 1.68 kGy. Verificat ion doses for different batches of processing were 5.87 to 9.46 kGy . All bone grafts exposed to the verification dose were tested culture negative. The results validate 25kGy dose for sterilizat ion of bone allografts processed fro m femo ral heads.
Highlights
Bone grafts are frequently used to revise skeletal defects by replacement o r aug mentation
Further since allografts do not compro mise normal structures, they avoid the s ign ificant mo rb id ity associated with the recovery of autologous bone graft
Femoral heads removed during hip replacement surgery are the most common source of allograft bone. 126 femo ral heads excised during surgery were included in the present study
Summary
Bone grafts are frequently used to revise skeletal defects by replacement o r aug mentation. Screening of donor for disease, bacterial testing and aseptic processing, substantially reduce risk, but do not completely eliminate the possibility of allograft associated infections. One of the principal advantages of radiation sterilizat ion arises fro m its ability to destroy contaminating microorganis ms with an insignificant rise in the temperature of the irradiated materials, thereby preserving the properties and characteristics of tissues. The efficacy of allograft sterilization is supported by the absence of bacterial or viral allograft-associated infections in tissue processed by this method[9]. The present study was carried out with the aim of microb iological evaluation of bone allografts processed from femoral heads and sterilized by gamma rad iation. The type and magnitude of microbial contamination associated with bone allografts and their resistance to gamma radiation was evaluated.
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