Microbiota Composition and Pulmonary Surfactant Protein Expression as Markers of Death by Drowning

Abstract

Pathological diagnosis of drowning remains a challenge for forensic science, because of a lack of pathognomonic findings. We analyzed microbiota and surfactant protein in the lungs for a novel diagnosis of drowning. All rats were divided into drowning, postmortem submersion, and control groups. The water, lungs, closed organs (kidney and liver), and cardiac blood in rats were assayed by targeting 16S ribosomal RNA of Miseq sequencing. Lung samples were analyzed by immunohistochemical staining for surfactant protein A. The closed organs and cardiac blood of drowned group have a lot of aquatic microbes, which have not been detected in postmortem submersion group. Furthermore, intra-alveolar granular staining of surfactant protein A (SP-A) was severely observed in the drowned group than the postmortem submersion and control groups. The findings suggested that the presence of aquatic microbiota in the closed organs and increased expression of SP-A could be markers for a diagnosis of drowning.

Microbial forensics: new breakthroughs and future prospects

“…The findings revealed that the microbial community in the closed organs was a significant marker for the diagnosis of death by drowning. Likewise, the same study hypothesized that drowning is associated with higher expression levels of surfactant protein A (regarded as a valuable marker of asphyxiation and acute lung injury) in the lung of true drowning victims (Lee et al 2017).…”

“…The diatoms' presence in blood or organs (e.g., lungs, kidneys, spleen, liver and bone marrow) from the victims has been frequently considered as the gold standard indicator for drowning cases, discriminating between antemortem immersion (live entry) and postmortem submersion (dumping of a dead body) or even indicating the location of a probable drowning place (seawater vs. freshwater diatoms) (Sitthiwong et al 2014;Spitz and Schneider 1964). However, this analysis presents several constraints: (i) diatoms may be present in low concentrations in some water sources, being difficult to detect even in some true drowning victims; (ii) some of these microorganisms present relatively large diameter/length (ranging between 2 and 500 μm), limiting their transposition of the alveolar wall and, consequently, their passage into the blood stream and organs; (iii) diatoms can be disclosed in several organs (e.g., kidney, liver and lungs) of nondrowned bodies (Calder 1984;Kakizaki et al 2010;Kakizaki et al 2009;Lee et al 2017).…”

“…These other microorganisms are much more abundant and present smaller sizes (ranging between 0.2 and 2 μm) than diatoms and, therefore, at least theoretically, would provide more informative results. A recent study compared lungs, closed organs (kidney and liver) and cardiac blood between antemortem immersion and postmortem submersion, either using MPS or the 16S rRNA gene and culture-dependent identification of aquatic microorganisms using matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) (Lee and Eom 2016;Lee et al 2017). The findings revealed that the microbial community in the closed organs was a significant marker for the diagnosis of death by drowning.…”

“…Another fundamental aspect in law enforcement and forensic researches is the distinction between primary and secondary crime scenes. While the first can be defined as the place where the criminal act was actually committed, the second is any other place (or places) related in a later time lapse, to this event (Lee et al 2001).…”

Microbiome in Death and Beyond: Current Vistas and Future Trends

“…Kakizaki et al (2012) used the 454 pyrosequencing approach to ascertain the cause of death of two drowning cases and found that it is possible to determine diverse aquatic microbes in drowning victims that can point toward the aquatic environment in which the drowning occurred. An animal study sampled for lungs, kidney, liver, and blood, and found significant aquatic microbial presence in the drowned group compared to closed organs of postmortem immersion group (Lee et al, 2017). Aquatic bacterial communities were further dominated by Proteobacteria (seawater), Bacteroidetes (freshwater), Actinobacteria, and Bacillariophyta (Lee et al, 2017).…”