Assessment of bioburden on human and animal tissues: Part 2—Results of testing of human tissue and qualification of a composite sample for routine bioburden determination

Abstract

A quantitative method was developed and validated to assess bioburden on tissue from human donors and to compare bioburden determination results to swab culture results from the same donor. An initial study with allograft tissue from 101 donors showed a wide range of bioburden levels; values from no colony-forming units (CFU) detected to >28,000 CFU were observed. Tissues from donors that had swab cultures negative for objectionable microorganisms generally had lower bioburden than tissues from donors where objectionable microorganisms were recovered by swab culturing. In a follow-up study with 1,445 donors, a wide range of bioburden levels was again observed on tissues from donors that were swab culture negative for objectionable microorganisms. Tissues from 885 (61%) of these donors had no recoverable bioburden (<2 CFU). Importantly, tissues from 560 (39%) of the donors had recoverable bioburden which ranged from 1 to >24,000 CFU. Identification of bioburden isolates showed a diversity of genera and species. In compliance with the recent revision of the American Association of Tissue Banks K2.210 Standard, the quantitative bioburden determination method was validated with a composite tissue sample that contains bone and soft tissue sections tested together in one extraction vessel. A recovery efficiency of 68% was validated and the composite sample was shown to be representative of all of the tissues recovered from a donor. The use of the composite sample in conjunction with the quantitative bioburden determination method will facilitate an accurate assessment of the numbers and types of contaminating microorganisms on allografts prior to disinfection/sterilization. This information will ensure that disinfection/sterilization processes are properly validated and the capability of the overall allograft process is understood on a donor by donor basis.

Systematic enhancement of microbial decontamination efficiency in bone graft processing by means of high hydrostatic pressure using Escherichia coli as a model organism

“…However, bone swaps, biopsies, and rinsing the transplant only give a rough estimate of the actual bioburden. This might be a reason for the great variations of 0 to concentrations rarely as high as 3.9 × 10 4 cfu/g or cfu/mL, respectively, as reported by several working groups 62–64 . Therefore, the minimum concentration for the artificial contamination of bone blocks was 1 × 10 4 cfu/mL within this study.…”

“…This might be a reason for the great variations of 0 to concentrations rarely as high as 3.9 Â 10 4 cfu/g or cfu/mL, respectively, as reported by several working groups. [62][63][64] Therefore, the minimum concentration for the artificial contamination of bone blocks was 1 Â 10 4 cfu/mL within this study. To efficiently determine the failure rate of high pressure decontamination, concentrations of up to 1 Â 10 8 cfu/mL were also tested.…”

Stabilization and Sterilization of Pericardial Scaffolds by Ultraviolet and Low-Energy Electron Irradiation

“…Additionally, LEEI was shown to be an effective procedure for inactivation of viruses by Fertey et al 22 Kowalski et al observed a bioburden estimate of up to 2.8 × 10 4 CFU on human and animal tissue grafts. 49 The bioburden determined in this study exceeds this value by one log 10 level. This difference may originate from the high precautions taken during removal of tissue grafts compared with tissue removal for meat production.…”

Radiation sterilization of tissue allografts: A review

“…[11] . Kowalski et al [12] carried out assessment of bioburden on tissue from 101 human donors and observed bioburden ranging up to > 28000 CFU. A number of studies have reported bacterial contamination of amniotic membrane [13,14] .…”