Influence of postmortem time on the outcome of blood cultures among cadaveric tissue donors

Current concepts for tissue transplant services for developing countries

The transplantation of tissues can save lives and re-establish vital functions, where no alternatives of comparable effectiveness exist. This has led to establishment of tissue transplantation as a successful practice worldwide; however, a great variability between countries remains in terms of donation levels, safety, quality of grafts and their efficacy. Tissue transplantation requires coordination of different agencies involved in the implementation of procurement, processing, storage and distribution of tissues and cells from different hospital units that perform surgical procedures with graft-type input requirements. This biomaterial-like requirement has led to the constant development of the area and today these graft products of human origin can be the starting point for new and more advanced biotechnological products. For long-term sustainability and successful transplantation units, a process management comparable to the pharmaceutical industry in terms of quality management systems must be established to produce safe and high-quality human-derived products. This review aims to update the current concepts of tissue transplant services for its application for developing countries using the current Chilean scenario as a case study. We summarize our findings proposing a set of guidelines/actions that should be followed to ensure smooth tissue transplant services implementations with high efficiency and safe use.

Determination of antibiotics and detergent residues in decellularized tissue-engineered heart valves using LC-MS/MS

Residual chemicals that are presented during tissue processing in human tissue banks can be a risk for the allograft recipient. Determine the residual concentrations of the antibiotics and detergent used in the process of human decellularized tissue-engineered heart valves stored in isotonic saline solution up to 18 months. A total of 24 human decellularized allografts were stored in sterile sodium chloride and analyzed immediately after the decellularization process (0 months) and after storage for 6, 12, and 18 months, which includes the use of sodium dodecyl sulfate (SDS) and antibiotics (cefoxitin, vancomycin hydrochloride, lincomycin hydrochloride, polymyxin B sulfate). These valves were used for suitability tests, the zone of inhibition evaluation, and direct contact cytotoxicity assay. The stock solution from 32 valves was used for LC-MS/MS analysis of antibiotics and SDS. Tissue samples from decellularized valves showed a zone of inhibition formation for S. aureus and B. subtilis, suggesting the presence of an inhibitory molecule in the tissue. Cytotoxicity tests were negative. Polymyxin B, vancomycin, and SDS were detected and quantified in human decellularized aortic and pulmonary allografts during all periods of the study. There were no traces of residual cefoxitin and lincomycin in the tissue stock solution. We found residual concentrations of the antibiotics and detergent used in the process of human decellularized tissue-engineered heart valves stored in isotonic saline solution up to 18 months.

Risk factors associated with contamination of allograft valves in a tissue bank

The contamination of the transport solution used in cardiovascular allografts can occur from different sources. Risk factors associated with positive microbiological test of transport solution have not been reported previously. This study aimed to determine the risk factor for contamination of transport solution used in the heart valve allografts stored in a Brazilian tissue bank. This retrospective study was conducted on all donors of cardiovascular allografts stored in a tissue bank from December 2008 to December 2017. Microbiological cultures for aerobic and anaerobic bacteria, fungi/yeasts were carried out in TS. Clinical variables were included. From 1001 transport solution, 52% were contaminated. A total of 770 microorganisms were identified, and Staphylococcus spp. was identified in 248 isolates (32.2%). Skin bacteria from skin microbiota were the most commonly identified microorganisms (Staphylococcus spp., Cutibacterium spp., Corynebacterium spp., and Bacillus spp.), occurring in 49.6%. The presence of a diagnosis of healthcare-associated infection was not associated with skin contamination (odds ratio [OR] 0.62 [0.41-0.94]; p = 0.014). Conditions like fever, use of antibiotics, and leukocytosis were less likely associated with contamination of transport solution. A longer warm ischemic time was associated with higher frequency of contamination. In the multivariable analysis, warm ischemic time was independently associated with contamination, and antibiotic therapy was a factor that decreased the rate of contamination (p < 0.05). Contamination of transport solution is associated with modifiable risk factors, such as warm ischemic time. Measures to minimize contamination should be employed to avoid unnecessary tissue discharges.

Implants induce a new niche for microbiomes

Although much work is being done to develop new treatments, research and knowledge regarding factors underlying implant-related microbial colonization leading to infection are less comprehensive. Presence of microorganisms in and around implants clinically characterized as uninfected remains unknown. The objective of this study was to detect and identify bacteria and fungi on implants from various groups of patients with no prior indications of implant related infections. Patient samples (implants and tissue) were collected from five different hospitals in the Capital region of Denmark. By in-depth microbiological detection methods, we examined the prevalence of bacteria and fungi on 106 clinically uninfected implants from four patient groups (aseptic loosening, healed fractures, craniofacial complications and recently deceased). Of 106 clinically uninfected implants and 39 negative controls investigated, 66% were colonized by bacteria and 40% were colonized by fungi (p < 0.0001 compared to negative controls). A large number of microbes were found to colonize the implants, however, the most prevalent microbes present were not common aetiological agents of implant infections. The findings indicate that implants provide a distinct niche for microbial colonization. These data have broad implications for medical implant recipients, as well as for supporting the idea that the presence of foreign objects in the body alters the human microbiome by providing new colonization niches.

Ancient human microbiomes

Very recently, we discovered a vast new microbial self: the human microbiome. Our native microbiota interface with our biology and culture to influence our health, behavior, and quality of life, and yet we know very little about their origin, evolution, or ecology. With the advent of industrialization, globalization, and modern sanitation, it is intuitive that we have changed our relationship with microbes, but we have little information about the ancestral state of our microbiome, and we therefore lack a foundation for characterizing this change. High-throughput sequencing has opened up new opportunities in the field of paleomicrobiology, allowing us to investigate the evolution of the complex microbial ecologies that inhabit our bodies. By focusing on recent coprolite and dental calculus research, we explore how emerging research on ancient human microbiomes is changing the way we think about ancient disease and how archaeological studies can contribute to a medical understanding of health and nutrition today.

The value of postmortem microbiology cultures

Since the inception of evidence-based scientific concepts in medicine in the 19th century, the utility of postmortem microbiologic examinations has been a topic of controversy. For every study describing a lack of correlation between antemortem clinical and laboratory findings and postmortem culture results, there is equal evidence from other studies that indicates at least some limited utility in select cases. While the contributions of autopsies and postmortem microbiologic examinations in the discovery of novel infectious microorganisms are generally appreciated by the medical and scientific societies, the problems of implementing routine procedures in daily autopsy practice clearly relate to the lack of consensus on their broader utility as well as to a lack of regulatory guidelines. This review provides an overview of the literature-based evidence regarding the utility of postmortem microbiologic examinations together with some practical aspects and guidelines for those confronted with the issue of whether to allow or discourage the use of bacteriologic cultures obtained during autopsies.

Comprehensive postmortem analyses of intestinal microbiota changes and bacterial translocation in human flora associated mice

Background

Postmortem microbiological examinations are performed in forensic and medical pathology for defining uncertain causes of deaths and for screening of deceased tissue donors. Interpretation of bacteriological data, however, is hampered by false-positive results due to agonal spread of microorganisms, postmortem bacterial translocation, and environmental contamination.

Methodology/Principal Findings

We performed a kinetic survey of naturally occurring postmortem gut flora changes in the small and large intestines of conventional and gnotobiotic mice associated with a human microbiota (hfa) applying cultural and molecular methods. Sacrificed mice were kept under ambient conditions for up to 72 hours postmortem. Intestinal microbiota changes were most pronounced in the ileal lumen where enterobacteria and enterococci increased by 3–5 orders of magnitude in conventional and hfa mice. Interestingly, comparable intestinal overgrowth was shown in acute and chronic intestinal inflammation in mice and men. In hfa mice, ileal overgrowth with enterococci and enterobacteria started 3 and 24 hours postmortem, respectively. Strikingly, intestinal bacteria translocated to extra-intestinal compartments such as mesenteric lymphnodes, spleen, liver, kidney, and cardiac blood as early as 5 min after death. Furthermore, intestinal tissue destruction was characterized by increased numbers of apoptotic cells and neutrophils within 3 hours postmortem, whereas counts of proliferative cells as well as T- and B-lymphocytes and regulatory T-cells decreased between 3 and 12 hours postmortem.

Conclusions/Significance

We conclude that kinetics of ileal overgrowth with enterobacteria and enterococci in hfa mice can be used as an indicator for compromized intestinal functionality and for more precisely defining the time point of death under defined ambient conditions. The rapid translocation of intestinal bacteria starting within a few minutes after death will help to distinguish between relevant bacteria and secondary contaminants thus providing important informations for routine applications and future studies in applied microbiology, forensic pathology, and criminal medicine.