Evaluation of Postmortem Bacterial Migration Using Culturing and Real‐Time Quantitative PCR

Abstract

Postmortem bacteriology can be a valuable tool for evaluating deaths due to bacterial infection or for researching the involvement of bacteria in various diseases. In this study, time-dependent postmortem bacterial migration into liver, mesenteric lymph node, pericardial fluid, portal, and peripheral vein was analyzed in 33 autopsy cases by bacterial culturing and real-time quantitative polymerase chain reaction (RT-qPCR). None suffered or died from bacterial infection. According to culturing, pericardial fluid and liver were the most sterile samples up to 5 days postmortem. In these samples, multigrowth and staphylococci were not or rarely detected. RT-qPCR was more sensitive and showed higher bacterial positivity in all samples. Relative amounts of intestinal bacterial DNA (bifidobacteria, bacteroides, enterobacter, clostridia) increased with time. Sterility of blood samples was low during the studied time periods (1-7 days). The best postmortem microbiological sampling sites were pericardial fluid and liver up to 5 days after death.

Time-dependent post mortem changes in the composition of intestinal bacteria using real-time quantitative PCR

“…The selection criteria for the autopsies have been described elsewhere [13]. None of the controls or cases was reported to has been used antibiotics.…”

“…were designed and confirmed by using BLAST (http://www.ncbi.nlm.nih.gov/) and Ribosomal Database Project (http://rdp.cme.msu.edu/probematch/search.jsp). Specificity and cross reactivity of the designed primers and probes were tested using bacterial cultures from clinical samples [13]. PCR assays were performed with AbiPrism 7000 HT Sequence Detection System (Taqman, AppliedBiosystems, California, USA) with Taqman Environmental MasterMix.…”

Postmortem succession of gut microbial communities in deceased human subjects

“…Clostridium spp. are normal members of the human gut microflora, and have been reported as a prominent members of postmortem microbial communities, including both internal organs and external sites (Hyde et al, 2015; Javan et al, 2016; Tuomisto et al, 2013; Cobaugh, Schaeffer & DeBruyn, 2015; Metcalf et al, 2013; Can et al, 2014). Another Clostridiales, Anaerosphaera spp., have been previously isolated from animal waste reactors and identified as aminolytic anaerobes, fermenting amino acids into volatile fatty acids (Ueki et al, 2009), implicating them as members of the putrefactive consortia as well.…”

“…Another Clostridiales, Anaerosphaera spp., have been previously isolated from animal waste reactors and identified as aminolytic anaerobes, fermenting amino acids into volatile fatty acids (Ueki et al, 2009), implicating them as members of the putrefactive consortia as well. Mouse model studies examining translocation of bacteria postmortem have demonstrated the migration and proliferation of Clostridium and other anaerobic taxa in the internal organs with increasing postmortem intervals (Heimesaat et al, 2012; Burcham et al, 2016); an increase in Clostridium in human internal organs postmortem has also been reported (Javan et al, 2016; Tuomisto et al, 2013). Clostridia are known putrefactive organisms, so their observed increase in relative abundance may be due to an increase in vegetative growth, where they gained energy through the fermentation of cellular products.…”

“…There has been recent interest in the use of microbial communities in the decomposition environment as markers of PMI: if the postmortem succession of microbial communities is repeatable and predictable, then it may be possible to use the communities as forensic indicators, similar to the approach taken by forensic entomology (Amendt, Krettek & Zehner, 2004). Recent studies have begun describing human postmortem microbial communities associated with a variety of habitats, including skin (Metcalf et al, 2016; Pechal et al, 2017; Hyde et al, 2015), mouth and rectum (Hyde et al, 2015; Hyde et al, 2013), ear and nasal canals (Johnson et al, 2016), internal organs (Javan et al, 2016; Tuomisto et al, 2013), bones (Damann, Williams & Layton, 2015) and soils below (Metcalf et al, 2016; Cobaugh, Schaeffer & DeBruyn, 2015). Other studies have also reported postmortem changes associated with decomposing animal carcasses (Pechal et al, 2013a; Metcalf et al, 2013; Heimesaat et al, 2012; Burcham et al, 2016; Dickson et al, 2011).…”