Evaluation of allograft contamination and decontamination at the Treviso Tissue Bank Foundation: A retrospective study of 11,129 tissues

Abstract

Microbiological contamination of retrieved tissues has become a very important topic and a critical aspect in the safety of allografts. We have analysed contamination in 11,129 tissues with a longitudinal contamination profile for each individual tissue. More specifically, 10,035 musculoskeletal tissues and 1,094 cardiovascular tissues were retrieved from a total of 763 multi-tissue donors, of whom 105 were heart-beating donors as well as organ donors, while the remaining 658 were non-heart beating donors and tissue donors only. All tissues were decontaminated twice, the first time immediately after retrieval and the second time after processing. Each tissue was submitted to microbiological culture three times, i.e., upon retrieval (Time 1), after the first decontamination (Time 2) and after the second decontamination (Time 3). The contamination rate for musculoskeletal tissues was 52%, 16.2% and 0.5% at Time 1, 2 and 3, respectively. The contamination rate for cardiovascular tissues was 84%, 42% and 6%. More than one strain was simultaneously present in 10.8% of musculoskeletal tissues and 44.6% of cardiovascular tissues. Out of 8,560 non-heart-beating donor musculoskeletal tissues, 4,689 (54.8%), 1,383 (16.2%) and 42 (0.5%) were contaminated at Time 1, Time 2 and Time 3, respectively. Out of 1,475 heart-beating donor musculoskeletal tissues, 522 (35.4%) 113 (7.7%) and 2 (0.1%) tissues were found to be contaminated at Time 1, 2 and 3, respectively. Out of 984 non-heart beating donor cardiovascular tissues, 869 (88.3%), 449 (45.6%) and 69 (7%) proved positive at Time 1, 2 and 3 respectively, while 50 (45.5%) and 10 (9.1%) heart-beating donor cardiovascular tissues were contaminated at Time 1 and 2. No tissue was contaminated at Time 3. Based on our methods, the two-step decontamination approach is mandatory in order to drastically reduce the number of tissues found to be positive at the end of the process.

Evaluation of allograft decontamination with two different antibiotic cocktails at the Treviso Tissue Bank Foundation

“…The results of the first decontamination cycle with cocktail A were comparable with earlier results published on tissue decontamination at our bank over a 4-year period, for both MST and CVT [26]. They also corroborated the findings of other authors that skin commensals [6, 27–31] and intestinal and respiratory tract flora [26,29,32] were the most commonly identified species in cadaveric tissue donors. In keeping with previous literature on tissue contamination, our results confirmed that a single decontamination step was not sufficient to eradicate all pathogens.…”

“…This prompted the need for a second decontamination, also taking into account that unclassified species among the non-compliers, which could potentially be eradicated by the antibiotic cocktail, were the main source of residual contamination. After the second decontamination step, cocktail B reduced the percentage of positive tissues far more than cocktail A, resulting in <2% and practically zero residual positivity (only 1 positive tissue) for CVT and MST, respectively, while cocktail A left higher percentages of positive tissues, in keeping with previous reports [26]. Ultimately, a lower number of both MST and CVT tissues tested positive post decontamination with cocktail B than with cocktail A.…”

Analysis of potential factors affecting allografts contamination at retrieval

“…Specifically, a more protracted cadaver time implies a higher risk of contamination and a higher probability that the tissue is contaminated by multiple strains. Accordingly, NHBD show a higher contamination rate and a higher number of tissues with multiple contaminations, as already previously reported (Paolin et al 2017 ). Moreover, this model of analysis has also shown that the period of the year during which retrieval takes place also plays a role.…”

“…In compliance with the existing literature (Deijkers et al 1997 ; Ireland and Spelman 2005 ; Jashari et al 2007 ; Paolin et al 2017 ; Tabaku et al 2004 ; Vehmeyer et al 2002 ), coagulase negative Staphylococcus strains are most frequently isolated and the presence of these skin commensals is probably due to external contamination at the time of retrieval, i.e., leakage from the skin incisions which are made to access the thoracic and abdominal cavities, exposure to the environment during retrieval and handling. Bacterial strains from intestinal and upper airways flora were also found.…”

“…7084 strains were isolated (1.22 strains per tissue on average). As already reported in previous papers (Deijkers et al 1997 ; Ireland and Spelman 2005 ; Jashari et al 2007 ; Paolin et al 2017 ; Tabaku et al 2004 ; Vehmeyer et al 2002 ), the main strains isolated in allografts were coagulase negative Staphylococci (65.7%), Streptococcus spp. (10.7%), Clostridium spp.…”