Postmortem bacteriology in forensic pathology: diagnostic value and interpretation

Method Validation Study of Dipstick Urinalysis as a Screening Tool for Sodium Nitrite Toxicity

ABSTRACT

The incidence of suicide by intentional nitrite ingestion has increased since 2017. Limited options exist for commercial laboratory analysis for nitrite/nitrate. This study investigates the use of urine dipsticks for screening at autopsy for potential toxicity with sodium nitrite and, less commonly, alkyl nitrite. Archived samples of blood, urine, vitreous fluid, and gastric contents from 4 sodium nitrite/nitrate cases, 3 alkyl nitrite cases, and 4 control cases were tested using dipsticks. A rapid, strong positive result for nitrite was in the vitreous fluid of all 4-sodium nitrite/nitrate cases, along with 2 positive urine and 1 positive gastric. The 2 alkyl nitrite inhalation toxicity cases had no positive results. One alkyl nitrite ingestion case had a positive urine. The 4 controls had negative urine: equivocal results in 2 vitreous, and 1 positive gastric. Urine dipsticks are a useful adjunct to laboratory testing for nitrite toxicity and provide a rapid, cost-effective tableside result that may guide the need for further testing. Vitreous fluid and urine appear to be the most reliable specimens, although testing of gastric liquid may be useful to corroborate oral ingestion. Dipsticks may not be a reliable adjunct for testing for alkyl nitrite toxicity via inhalation route, likely due to the much lower nitrite concentration compared to nitrite ingestion cases.

Forensic Microbiology: When, Where and How

Forensic microbiology is a relatively new discipline, born in part thanks to the development of advanced methodologies for the detection, identification and characterization of microorganisms, and also in relation to the growing impact of infectious diseases of iatrogenic origin. Indeed, the increased application of medical practices, such as transplants, which require immunosuppressive treatments, and the growing demand for prosthetic installations, associated with an increasing threat of antimicrobial resistance, have led to a rise in the number of infections of iatrogenic origin, which entails important medico-legal issues. On the other hand, the possibility of detecting minimal amounts of microorganisms, even in the form of residual traces (e.g., their nucleic acids), and of obtaining gene and genomic sequences at contained costs, has made it possible to ask new questions of whether cases of death or illness might have a microbiological origin, with the possibility of also tracing the origin of the microorganisms involved and reconstructing the chain of contagion. In addition to the more obvious applications, such as those mentioned above related to the origin of iatrogenic infections, or to possible cases of infections not properly diagnosed and treated, a less obvious application of forensic microbiology concerns its use in cases of violence or violent death, where the characterization of the microorganisms can contribute to the reconstruction of the case. Finally, paleomicrobiology, e.g., the reconstruction and characterization of microorganisms in historical or even archaeological remnants, can be considered as a sister discipline of forensic microbiology. In this article, we will review these different aspects and applications of forensic microbiology.

Applications of microbiology to different forensic scenarios - A narrative review

In contrast to other forensic disciplines, forensic microbiology is still too often considered a "side activity" and is not able to make a real and concrete contribution to forensic investigations. Indeed, the various application aspects of this discipline still remain a niche activity and, as a result, microbiological investigations are often omitted or only approximated, in part due to poor report in the literature. However, in certain situations, forensic microbiology can prove to be extremely effective, if not crucial, when all other disciplines fail. Precisely because microorganisms can represent forensic evidence, in this narrative review all the major pathological forensic applications described in the literature have been presented. The goal of our review is to highlight the versatility and transversality of microbiology in forensic science and to provide a comprehensive source of literature to refer to when needed.

Exploration of sepsis assisting parameters in hospital autopsied-patients: a prospective study

Although Sepsis-3 doesn't require evidence of bacteremia to diagnose sepsis, clinicians often want to identify the causative pathogen at autopsy. In principle, if the blood cultures are the same at ante- and postmortem, the cause of death is obvious. However, interpretations of postmortem blood cultures are often difficult due to discordance, negativity, mixed infection, and contamination, of pathogens occupying ≥ 50% of the tests. To increase specificity identifying agonal phase sepsis in the situations where blood cultures are discordant, multiple or negative at postmortem, we established a scoring system using blood cultures, procalcitonin (PCN) showing highest sensitivity and specificity for postmortem serum, and bone marrow polyhemophagocytosis (PHP). Histological sepsis showed significantly higher levels of culture score (2.3 ± 1.5 vs. 0.4 ± 0.5, p < 0.001), PHP score (2.5 ± 0.8 vs. 1.0 ± 1.1, p < 0.001), and PCN score (1.8 ± 0.8 vs. 0.8 ± 0.6, p < 0.01) than non-septic patients. Receiver operating characteristic curve analysis indicated that estimation of three scores was the most reliable indicator for recognizing agonal phase sepsis. These findings suggest that the combination of these three inspections enables to determine the pathological diagnoses of sepsis even it is not obvious by discordant, mixed or negative blood cultures.

Utility of postmortem bacterial culture of abdominal organs at autopsy of young calves

Postmortem bacterial culture is controversial in human medicine, and veterinary-specific research in this area is lacking. To address this knowledge gap, we cultured liver, kidney, and spleen individually from on-farm calf mortalities to determine the number of bacterial species present, concordance between organ cultures, and agreement with gross and histologic findings. We hypothesized that the spleen, a filtering organ, would be the most useful organ with the least amount of postmortem contamination given that it does not have a direct conduit to a bacterial population. Fresh liver, kidney, and spleen were collected for culture from 30 calves 5-28-d-old with various causes of mortality. Bacterial growth of ≥2 species was observed in ~48% of cultures, with Escherichia coli and Streptococcus spp. being most frequent. One bacterial species was present in 20% of cultures, with E. coli predominating. No growth was observed in ~32% of cultures. In 43% of cases, there was agreement in the culture results for all 3 organs; however, the majority were mixed bacterial growth. The best agreement was observed when there were no gross and/or histologic septic lesions in target organs and no bacterial growth on culture. The spleen was not helpful in determining bacterial significance in comparison to kidney or liver.

Utility and diagnostic value of postmortem microbiology associated with histology for forensic purposes

Nowadays, the diagnostic value of postmortem microbiological investigations is still a debated topic, but postmortem microbiology (PMM) remains a discipline with great forensic potential. To evaluate the usefulness and diagnostic-forensic value of postmortem microbiological cultures, it has been conducted a study on cadaveric material sampled during autopsy aiming to identify the correct cause of death. The study analyzed 45 cadavers subjected to judicial autopsy, divided into two groups based on the presence or absence of external or internal macroscopic autopsy signs suggesting infectious pathology. In the same cases, both the microbiological and conventional histological investigations have been simultaneously carried out. From the investigations, mono-bacterial, mono-fungal, mixed and negative cultures were observed. In mono-species microbiological growth, the histological epicrisis confirmed an infectious cause of death due to the presence of signs of acute infection with an aggressive infectious agent. In cases where growth was mixed, it was possible to distinguish between simple postmortal contamination and perimortem colonization. Finally, in some cases where the microbiology was negative, this has been essential in highlighting signs of a vital reaction to viral or parasitic infection. The joint and integrated evaluation of the laboratory results made it possible to correctly understand even those peculiar situations in which the PMM results alone would not have been significant. These methods, when combined, constitute an optimal forensic approach for the identification of the real cause of death and thus reduce the number of unsolved cases.

Postmortem Bacteriology in Forensic Autopsies—A Single Center Retrospective Study in Romania

Postmortem bacteriology examinations have been a controversial topic over the years, though the value of postmortem bacteriology cultures remains promising. The aim of this study was to review the postmortem bacteriological sampling procedures and results in a single centre in Bucharest over a period of 10 years. Material and methods: The present study was a retrospective, single-center study, performed at the Mina Minovici National Institute of Legal Medicine in Bucharest, Romania, from 2011–2020. Results: Postmortem bacteriology was requested 630 forensic autopsies, 245 female (38.9%) and 385 male (61.1%), age range 0 and 94 years, median age of 52 years. Deaths occurred in hospital for 594 cases (94.3%) and out-of-hospital for 36 cases (5.7%—field case). Blood cultures were requested in the majority of cases, followed by tracheal swabs and lung tissue. In-hospital and out of hospital deaths did not differ significantly regarding the number of microorganisms identified in a positive blood culture. Postmortem bacteriology cultures of the respiratory tract showed a statistically significant association to microscopically confirmed lung infections. Conclusions Postmortem sampling for bacteriology testing in our center in Bucharest is heterogeneous with a high variation of patterns. A positive blood culture result for Staphylococcus species without the identification of a specific microorganism is more likely due to postmortem contamination.

Symbiotic microbes and potential pathogens in the intestine of dead southern right whale (Eubalaena australis) calves

Between 2003 and 2017, at least 706 southern right whale (Eubalaena australis) calves died at the Península Valdés calving ground in Argentina. Pathogenic microbes are often suggested to be the cause of stranding events in cetaceans; however, to date there is no evidence supporting bacterial infections as a leading cause of right whale calf deaths in Argentina. We used high-throughput sequencing and culture methods to characterize the bacterial communities and to detect potential pathogens from the intestine of stranded calves. We analyzed small and large intestinal contents from 44 dead calves that stranded at Península Valdés from 2005 to 2010 and found 108 bacterial genera, most identified as Firmicutes or Bacteroidetes, and 9 genera that have been previously implicated in diseases of marine mammals. Only one operational taxonomic unit was present in all samples and identified as Clostridium perfringens type A. PCR results showed that all C. perfringens isolates (n = 38) were positive for alpha, 50% for beta 2 (n = 19) and 47% for enterotoxin (CPE) genes (n = 18). The latter is associated with food-poisoning and gastrointestinal diseases in humans and possibly other animals. The prevalence of the cpe gene found in the Valdés' calves is unusually high compared with other mammals. However, insufficient histologic evidence of gastrointestinal inflammation or necrosis (the latter possibly masked by autolysis) in the gut of stranded calves, and absence of enterotoxin detection precludes conclusions about the role of C. perfringens in calf deaths. Further work is required to determine whether C. perfringens or other pathogens detected in this study are causative agents of calf deaths at Península Valdés.

Postmortem microbiology sampling following death in hospital: an ESGFOR task force consensus statement

Postmortem microbiology (PMM) is a valuable tool in the identification of the cause of death and of factors contributory to death where death has been caused by infection. The value of PMM is dependent on careful autopsy planning, appropriate sampling, minimisation of postmortem bacterial translocation and avoidance of sample contamination. Interpretation of PMM results requires careful consideration in light of the clinical history, macroscopic findings and the histological appearances of the tissues. This consensus statement aims to highlight the importance of PMM in the hospital setting and to give microbiological and pathological advice on sampling in deaths occurring in hospital.

Postmortem Interval and Diagnostic Performance of the Autopsy Methods

Postmortem studies, including the complete diagnostic autopsy (CDA) and the minimally invasive autopsy (MIA), an innovative approach to post-mortem sampling and cause of death investigation, are commonly performed within 24 hours after death because the quality of the tissues deteriorates over time. This short timeframe may hamper the feasibility of the procedure. In this study, we compared the diagnostic performance of the two postmortem procedures when carried out earlier and later than 24 hours after death, as well as the impact of increasing postmortem intervals (PMIs) on the results of the microbiological tests in a series of 282 coupled MIA/CDA procedures performed at the Maputo Central Hospital in Mozambique between 2013 and 2015. 214 procedures were conducted within 24 hours of death (early autopsies), and 68 after 24 hours of death (late autopsies). No significant differences were observed in the number of non-conclusive diagnoses (2/214 [1%] vs. 1/68 [1%] p = 0.5645 for the CDA; 27/214 [13%] vs. 5/68 [7%] p = 0.2332 for the MIA). However, increasing PMIs were associated with a raise in the number of bacteria identified (rate: 1.014 per hour [95%CI: 1.002–1.026]; p = 0.0228). This increase was mainly due to rising numbers of bacteria of the Enterobacteriaceae family and Pseudomonas genus strains. Thus, performing MIA or CDA more than 24 hours after death can still render reliable diagnostic results, not only for non-infectious conditions but also for many infectious diseases, although, the contribution of Enterobacteriaceae and Pseudomonas spp. as etiological agents of infections leading to death may be overestimated.

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.

Positive Bacteriological Analyses in Individuals With Diabetes Mellitus: Preliminary Results From a Forensic Study

Increased infection susceptibility in the diabetic population is a controversial issue in the clinical field. The greater frequency of infections in diabetic patients has been speculated as caused by the hyperglycemic environment that favors immune dysfunction. The aim of this study was to investigate the proportion of positive bacterial cultures in a series of diabetic individuals who underwent forensic investigations and assess the frequency of hyperglycemia at the time of death in these cases as well as the percentage of diabetics with cause of death due to bacterial infection. Forensic autopsy cases characterized by positive bacterial cultures and pre-existing diagnosis of diabetes mellitus were included in the study. Initial findings revealed that 12% (7/58 cases) of positive bacterial cultures concerned individuals with a pre-existing diagnosis of diabetes mellitus. Bacterial infection was considered to be the cause of death in 22% (7/31 cases) of diabetics with positive bacterial cultures. Hyperglycemia could be identified in 1 case only at the time of death. These preliminary results highlight the usefulness of systematically performing postmortem bacteriology in the forensic setting to more precisely characterize infectious risk factors in diabetics.

Simple detection of bacterioplankton using a loop-mediated isothermal amplification (LAMP) assay: First practical approach to 72 cases of suspected drowning

We developed a novel molecular tool for assisting the diagnosis of death by drowning and evaluated its validity in forensic practical cases. Two novel sets of loop-mediated isothermal amplification (LAMP) primers were designed to detect either representative freshwater (Aeromonas) or marine (Vibrio, Photobacterium, Listonella) bacterioplankton (aquatic bacteria) in one tube using the LAMP technique. The assay involves only mixing template DNA with seven reagents and incubating at 64°C for 80min and does not require special or expensive equipment because detection is based on visual observation under natural light. The assay's excellent specificity was also demonstrated using 17 standard (control) strains and 124 other bacterial strains cultured from drowning and non-drowning victims in our previous studies. We then assayed 299 specimens (135 lung, 164 blood) from 72 victims, including 45 who had drowned in rivers, ditches, seas, and around estuaries. LAMP assay results could provide effective information to assist the diagnosis of death by drowning in practical cases. The LAMP assay would be useful for suspected drowning cases, as it is a less-laborious and less-expensive minimal test when death by drowning is sufficiently confirmed or negated from only autopsy findings and environmental data or when diatom testing is not performed due to logistic, personnel, or budgetary limitations. Moreover, the assay could serve as a simple additional test when the density of diatoms in the lungs is very low due to low density in the water.

A systematic review exploring the relationship between infection and sudden unexpected death between 2000 and 2016: A forensic perspective

Death due to infectious diseases is a major health concern worldwide. This is of particular concern in developing countries where poor-socio economic status and a lack of healthcare resources contribute to the high burden of disease. In some cases death due to infection can be acute and aggressive, and death may occur without a diagnosis whilst the person is still alive. These deaths may ultimately lead to a medico-legal autopsy being performed. There are various mechanisms by which sudden death due to infection may occur. In addition, there are many risk factors associated with sudden death due to infection, which differ between infants and older individuals. However, it is unclear which pathogens and risk factors are most frequently associated with sudden death due to infection. Therefore a systematic review of articles and case reports published between 1 January 2000 and 30 June 2016 was undertaken in order to (1) explore the relationship between pathogens and their causative role and (2) identify the relationship between predisposing and/or risk factors associated with sudden death due to infection. Major databases were searched and after critical appraisal 143 articles were identified. It was found that respiratory infections and deaths involving bacterial pathogens were most commonly associated with these deaths. In addition the most common risk factors in infants were exposure to tobacco smoke and co-sleeping. In adults the most common risk factors were co-morbid conditions and illnesses. This information aids in a better understanding of these deaths and highlights the need for more research in this field, particularly in developing countries.

Post-mortem detection of bacteremia using pairs of blood culture samples

AIM

The objective of this study was to assess the utility of examining pairs of blood culture samples obtained from separate sites (both ventricles or the aorta and vena cava) for detecting bacteremia in the post-mortem setting.

METHODS

Autopsy cases in which bacterial species were isolated from blood cultures were identified over a 4-year period. Ante-mortem and post-mortem records and the findings of pathological examinations were reviewed.

RESULTS

Overall, 23 bacterial species were detected in 18 autopsy cases. E. coli was the most commonly detected species (5 cases, 27.8%), followed by S. aureus and K. pneumoniae, respectively. Seven of the detected bacterial species (3 cases, 16.7%) were obligate anaerobes (Clostridium spp. and Bacteroides spp.). Among the 3 cases involving obligate anaerobes, multiple bacterial species were detected in 2 cases. Clinically, 2 of the 18 patients in which bacteria were detected were treated for significant infections (urosepsis, pneumonia, and catheter-related bloodstream infection) before their deaths. Seven cases exhibited evidence of significant infection during the post-mortem pathological examination. The differences between the aerobic and anaerobic bacteria positivity rates of the single and paired blood culture samples were significant (aerobic: p=0.013 and anaerobic: p=0.018).

CONCLUSION

Analyzing pairs of blood culture samples obtained from separate sites is useful for detecting bacteremia during post-mortem examinations.

Autopsy Prevalence of Tuberculosis and Other Potentially Treatable Infections among Adults with Advanced HIV Enrolled in Out-Patient Care in South Africa

Background

Early mortality among HIV-positive adults starting antiretroviral therapy (ART) remains high in resource-limited settings, with tuberculosis (TB) the leading cause of death. However, current methods to estimate TB-related deaths are inadequate and most autopsy studies do not adequately represent those attending primary health clinics (PHCs). This study aimed to determine the autopsy prevalence of TB and other infections in adults enrolled at South African PHCs in the context of a pragmatic trial of empiric TB treatment (“TB Fast Track”).

Methods and Findings

Adults with CD4 ≤150 cells/μL, not on ART or TB treatment, were enrolled to TB Fast Track and followed up for at least six months. Minimally invasive autopsy (MIA) was conducted as soon as possible after death. Lungs, liver, and spleen were biopsied; blood, CSF, and urine aspirated; and bronchoalveolar lavage fluid obtained. Samples underwent mycobacterial, bacterial, and fungal culture; molecular testing (including Xpert® MTB/RIF); and histological examination. 34 MIAs were conducted: 18 (53%) decedents were female; median age was 39 (interquartile range 33–44) years; 25 (74%) deaths occurred in hospitals; median time from death to MIA was five (IQR 3–6) days. 16/34 (47%) had evidence of TB (14/16 [88%] with extrapulmonary disease; 6/16 [38%] not started on treatment antemortem); 23 (68%) had clinically important bacterial infections; four (12%) cryptococcal disease; three (9%) non-tuberculous mycobacterial disease; and two (6%) Pneumocystis pneumonia. Twenty decedents (59%) had evidence of two or more concurrent infections; 9/16 (56%) individuals with TB had evidence of bacterial disease and two (13%) cryptococcal disease.

Conclusions

TB, followed by bacterial infections, were the leading findings at autopsy among adults with advanced HIV enrolled from primary care clinics. To reduce mortality, strategies are needed to identify and direct those at highest risk into a structured pathway that includes expedited investigation and/or treatment of TB and other infections.

Sudden Natural Death: Infectious Diseases

A large number of sudden and unexpected deaths are caused by infections. Bacterial and viral infections remain the most common causes of sudden death from infectious diseases. Sudden deaths resulting from infectious causes involving the cardiovascular system are commonly reported due to myocarditis and infective endocarditis while sudden deaths involving the respiratory system are mostly due to pneumonia and tuberculosis. Detailed medicolegal investigation is warranted in sudden deaths due to infectious diseases involving a thorough autopsy and histopathological evaluation along with the use of microbiology and molecular diagnostic methods.

Bacterial Translocation and Sample Contamination in Postmortem Microbiological Analyses

The diagnostic value of postmortem bacteriology has been discussed controversially for decades. In the study herein, contamination during sampling procedures and postmortem translocation were investigated to interpret postmortem microbiology results. One hundred medicolegal autopsy cases in total were included. Radiology, histology, bacteriology, and biochemistry were performed in all cases. Based on all investigation findings, 4 groups of cases were identified: death unrelated to infection, true infections, false positive (contamination during sampling procedures, postmortem translocation and mixed situations), and undetermined. The results of this study indicate that postmortem bacteriology provides useful data supporting infection-related deaths, especially when potentially significant observations are accompanied by consistent autopsy, histology, and biochemistry. Result interpretation requires careful evaluation of number and type of isolated microorganisms.

The importance of microbiological testing for establishing cause of death in 42 forensic autopsies

Microorganisms have always been one of the great challenges of humankind, being responsible for both high morbidity and mortality throughout history. In a forensic setting microbiological information will always be difficult to interpret due to lack of antemortem information and changes in flora postmortem. With this study we aim to review the use of microbiological procedures at our forensic institute. In a retrospective study including 42 autopsies performed at our Institute, where microbiological test had been applied, analyses were made with regard to: type of microbiological tests performed, microorganisms found, histological findings, antemortem information, C-reactive protein measurement and cause of death. Fiftyone different microorganisms were found distributed among 37 cases, bacteria being the most abundant. Nineteen of the cases were classified as having a microbiological related cause of death. C-reactive protein levels were raised in 14 cases of the 19 cases, histological findings either supported or were a decisive factor for the classification of microbiologically related cause of death in 14 cases. As a multitude of abundant microorganisms are able to cause infection under the right circumstances, all findings should be compared to anamnestic antemortem information, before conclusions are drawn. A definite list of true pathogens is nearly impossible to compile.

Fatal sepsis by Klebsiella pneumoniae in a patient with systemic lupus erythematosus: the importance of postmortem microbiological examination for the ex post diagnosis of infection

The utility of postmortem microbiology has continuously been a topic of controversy. The present study describes a case of fatal sepsis in a patient with systemic lupus erythematosus. Postmortem culture and genotyping analyses allowed us to identify Klebsiella pneumoniae as the cause of sepsis, revealing the inadequateness of antimicrobial therapy.

Cerebrospinal fluid PCR analysis and biochemistry in bodies with severe decomposition

The aim of this study was to assess whether Neisseria meningitidis, Listeria monocytogenes, Streptococcus pneumoniae and Haemophilus influenzae can be identified using the polymerase chain reaction technique in the cerebrospinal fluid of severely decomposed bodies with known, noninfectious causes of death or whether postmortem changes can lead to false positive results and thus erroneous diagnostic information. Biochemical investigations, postmortem bacteriology and real-time polymerase chain reaction analysis in cerebrospinal fluid were performed in a series of medico-legal autopsies that included noninfectious causes of death with decomposition, bacterial meningitis without decomposition, bacterial meningitis with decomposition, low respiratory tract infections with decomposition and abdominal infections with decomposition. In noninfectious causes of death with decomposition, postmortem investigations failed to reveal results consistent with generalized inflammation or bacterial infections at the time of death. Real-time polymerase chain reaction analysis in cerebrospinal fluid did not identify the studied bacteria in any of these cases. The results of this study highlight the usefulness of molecular approaches in bacteriology as well as the use of alternative biological samples in postmortem biochemistry in order to obtain suitable information even in corpses with severe decompositional changes.

Postmortem angiography using femoral cannulation and postmortem microbiology

Despite the undeniable advantages of postmortem angiography, numerous questions have arisen concerning the influence that the injected contrast media may exercise on biological fluids and tissues collected for toxicological and biochemical investigations. Moreover, cardiac blood for microbiological investigations cannot be obtained post-angiography. In this study, we examined whether the peripheral blood collected prior to postmortem angiography, using percutaneous access to femoral vessels after skin surface disinfection, could be suitable for microbiological investigations when postmortem angiography with femoral vessel cannulation is also performed. A total of 66 cases were included in the study and were divided into two subgroups (angiography and bacteriology group, 33 cases and control group, 33 cases). Autopsies, histology, toxicology, bacteriology, and biochemical investigations (procalcitonin, C-reactive protein, interleukin-6, and soluble triggering receptors expressed on myeloid cells type 1) were performed in all cases. No statistically significant differences between the two groups were noted, and identified category distribution (death unrelated to infection, true infection, false positive, and undetermined) was rather similar in both studied populations. These preliminary results suggest that postmortem angiography using a femoral approach does not constitute an impediment to the collection of peripheral blood for microbiology and vice versa. Moreover, the use of femoral blood for microbiology does not lead to an increased risk of doubtful results.

Markers for sepsis diagnosis in the forensic setting: state of the art

Reliable diagnoses of sepsis remain challenging in forensic pathology routine despite improved methods of sample collection and extensive biochemical and immunohistochemical investigations. Macroscopic findings may be elusive and have an infectious or non-infectious origin. Blood culture results can be difficult to interpret due to postmortem contamination or bacterial translocation. Lastly, peripheral and cardiac blood may be unavailable during autopsy. Procalcitonin, C-reactive protein, and interleukin-6 can be measured in biological fluids collected during autopsy and may be used as in clinical practice for diagnostic purposes. However, concentrations of these parameters may be increased due to etiologies other than bacterial infections, indicating that a combination of biomarkers could more effectively discriminate non-infectious from infectious inflammations. In this article, we propose a review of the literature pertaining to the diagnostic performance of classical and novel biomarkers of inflammation and bacterial infection in the forensic setting.

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.

Evaluation of postmortem bacterial migration using culturing and real-time quantitative PCR

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.

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.

Air, water, and surface bacterial contamination in a university-hospital autopsy room

Today, little is known about the bacteriological environment of the autopsy room and its potential interest for medico-legal practices. Seven hundred fifty microbiological samples were taken from surface (n = 660), air (n = 48), and water (n = 42) to evaluate it in a French University Forensic Department. Median bacterial counts were compared before and during autopsy for air samples, and before and after autopsy for surface samples, using Wilcoxon matched pairs signed ranks test. Bacterial identification relied on traditional phenotypic methods. Bacterial counts in the air were low before autopsy, increased significantly during procedure, and seemed more linked to the number of people in the room than to an important production of aerosol-containing bacteria. Despite cleaning, human fecal flora was omnipresent on surfaces, which revealed insufficient disinfection. Bacteriological sampling is an easy way to monitor cleaning practices in postmortem rooms, but chiefly a way to improve the reliability of medico-legal proofs of infectious deaths.

The influence of putrefaction and sample storage on post-mortem toxicology results

There are numerous biochemical and biological processes that occur after death that may have a significant influence on post-mortem drug concentrations. These processes may render the quantification of particular drugs unreliable, or even result in drugs being undetectable in some instances, despite the use of several methods. Problems may occur with changes in the drug concentration via bacterial degradation, residual tissue enzymatic activity, or via post-mortem redistribution from tissues of a higher to a lower concentration. Many analytical techniques can suffer from interferences due to co-extracted putrefactive compounds that mask or alter the way a drug is detected, depending on the analytical technique utilised. The following paper reviews problems associated with post-mortem drug concentration changes, and the significance of microbial influences during the post-mortem interval and sample storage.

Sudden adult death

In the investigation of sudden death in adults, channelopathies, such as long QT syndrome, have risen to the fore in the minds of forensic pathologists in recent years. Examples of these disorders are touched upon in this review as an absence of abnormal findings at postmortem examination is characteristic and the importance of considering the diagnosis lies in the heritable nature of these conditions. Typically, a diagnosis of a possible channelopathy is evoked as an explanation for a 'negative autopsy' in a case of apparent sudden natural death. However, the one potential adverse effect of this approach is that subtle causes of sudden death may be overlooked. The intention of this article is to review and discuss potential causes of sudden adult death (mostly natural) that should be considered before resorting to a diagnosis of possible channelopathy. Nonetheless, it becomes apparent that many of the potential causes of sudden death can have a genetic basis. Thus, it becomes an important consideration that there may be a genetic basis to sudden death that extends beyond the negative autopsy.

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

Tissue banks provide tissues of human cadaver donors for transplantation. The maximal time limit for tissue retrieval has been set at 24 h postmortem. This study aimed at evaluating the evidence for this limit from a microbiological point of view. The delay of growth in postmortem blood cultures, the identification of the species isolated and clinical/environmental factors were investigated among 100 potential tissue donors. No significant difference was found in the rate of donors with grown blood cultures within (25/65=38%) compared with after (24/65=37%) 24 h of death. Coagulase-negative staphylococci and gastro-intestinal microorganisms were isolated within and after 24 h of death. Two factors--antimicrobial therapy and "delay before body cooling"--were significantly inversely related with donors' blood culture results. From a microbiological point of view, there is no evidence for avoiding tissue retrieval among donors after 24 h of death.

Insights into the origin of postmortem ethanol

Accurate interpretation of the blood ethanol (EtOH) concentration at the time of death presents a difficult task since the origin of detected EtOH in postmortem cases (either in corpses or in specimens after sample collection) may vary. Headspace gas chromatography is the choice method for detecting EtOH in blood or other specimens, due to the accuracy and sensitivity it provides. Possible sources of postmortem EtOH have been the ante-mortem ingestion, the ante-mortem endogenous production and the postmortem microbial neo-formation, which has been considered the most critical factor that could complicate the results. It has been reported that EtOH could be formed postmortem in variable and non-predictable amounts, as a function of the type and number of microorganisms present either in corpses or specimens collected at autopsy. The presence of other volatiles-mostly n-propanol-has been correlated to microbial EtOH production, although the quantitative pattern between them and EtOH still remains obscure. The factors most frequently implicated in the mechanism of postmortem EtOH production in corpses have been considered the number and nature of microbes present, the availability of various types of substrates, the temperature and the time. Complication in the interpretation of blood alcohol concentration could arise due to the atypical distribution of EtOH in the body compartments after death. Specimens to blood EtOH ratios reported in the literature are presented. All the aforementioned aspects are discussed in a comprehensive way, providing a deep insight into this essential problem.

Postmortem serum endotoxin level in relation to the causes of death

Serum endotoxin is a clinical marker of sepsis. However, it is vulnerable to bacterial contamination, and the postmortem stability has not been established. In the present study, to evaluate the forensic pathological significance of postmortem endotoxemia in relation to the causes of death, we investigated a series of 111 autopsy cases (postmortem interval<48 h), in part, using bacteriological investigations. Systemic endotoxemia involving both the cardiac and peripheral blood was observed in some specific causes of death, including pneumonia (n=1/3), peritonitis (n=2/5), delayed traumatic death with severe secondary infection (n=7/33), drownings (freshwater, n=3/9; saltwater, n=3/16), fire deaths (n=3/16), and also in protracted deaths under critical medical care (n=2). Most cases of fatal blunt injury (n=4/5) showed sporadic endotoxemia in cardiac or peripheral blood, whereas there was no elevation of serum endotoxin in acute hemorrhagic death from sharp instrument injury (n=6). The bacteriological investigation showed some characteristic profiles in infections and drownings. These observations suggested that, although endotoxin is a vulnerable serum marker to ante and postmortem interference, systemic postmortem endotoxemia involving peripheral blood may be a possible indicator of antemortem bacteremia related to some specific causes of death accompanied by advanced infection or pulmonary alveolar damage in the dying process especially due to drownings and fires.

Fatal Waterhouse-Friderichsen syndrome due to Ewingella americana infection

A fatal case of Waterhouse-Friderichsen syndrome resulting from infection in a previously healthy 74-year-old woman is reported. The patient died suddenly within 14 hours after presentation. The diagnosis of Waterhouse-Friderichsen syndrome as the cause of death was established post mortem based on autopsy findings, microscopic examination, measurement of serum procalcitonin concentration (113 ng/ml), and outcome of postmortem bacteriologic cultures that grew in heart and spleen blood samples. Since the introduction of as a new group in the family in 1983, more recent case studies have established its clinical significance and pathogenic potential to cause severe, life-threatening bacteremia and sepsis. is a rare pathogen that should be added to the list of unusual bacteria causing Waterhouse-Friderichsen syndrome.