Radiation Response of Bacteria Associated with Human Cancellous Bone

Cancellous bones from twenty five live tissue donors were tested for bacterial contamination and initial bioburden ranged from 4.1×10 to 3.1×10 cfu/g (average 9.0×10 cfu/g). Forty six representative bacterial isolates were characterized on the basis of morphological, cultural and biochemical characteristics. Staphylococcus spp. was found to be predominant contaminant in tissue samples (41.30%). To assess the radiation resistance all the bacterial isolates were exposed to 1 to 10 kGy gamma radiation from 60 Co gamma source. The radiation decimal reduction dose values (D10) and twelve log reduction values (12 D value) of the isolates were calculated. D10 values of the isolates were ranged from 0.59 to 1.20 kGy. Among the studied bacterial isolates, Streptococcus spp. was the most radioresistant isolates (D10 value 0.93-1.20 kGy) and three of the Streptococcus spp. survived up to 8 kGy. All the bacterial isolates were killed at 9 kGy. Twelve log reduction value (12D value) of the most resistant isolate was 14.4 kGy. These results indicate that standard radiation sterilization dose (25 kGy) is satisfactory for the sterilization of the cancellous bone allografts. KeywordsBioburden, Cancellous bone, Radiation resistance, Staphylococcus, Streptococcus, Sterilization