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

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.

[Use of microbiological data for the purposes of forensic medical examination]

The study objective was to describe the formation of forensic microbiological examination as an analysis of a new type, defined as the detection and registration of reliably measured environmental and physiological changes within the microbial community of corpse in order to substantiate the possibility of using microbiological parameters to establish the prescription of death coming. It has been determined that the knowledge of the patterns of interaction of a human and his corpse with endogenous and exogenous flora provides the basis for solving a number of traditional and new application-oriented expert tasks and the allocation of such a variety of forensic examination as forensic microbiological examination. Endogenous and exogenous human flora and its interaction with living and dead biological tissues are the objects of this kind of examination, and the dynamic patterns of such interaction are the subject of study. One of the initial relevant tasks of forensic microbiological examination consists in development of methods, adequate for the expert task to be solved, choice of the research «target», «models» for comparative analysis and medium, adequate for task in hand, as well as certification of these methods and standardization of assessment criteria for the obtained results.

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.

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.

Fatal Pediatric Streptococcal Infection: A Clinico-Pathological Study

PURPOSE AND CONTEXT

Streptococcal Infection (SI) is an important cause of pediatric death in children, yet limited reports exist on autopsy findings in fatal SI cases.

METHOD

Case records (1997-2019) of SI with no pre-existing risk factors were reviewed and selected. Their clinical and pathological findings in the autopsy reports were analyzed.

RESULTS

In our cohort of 38 cases based on bacterial culture results, SI was most commonly caused by Streptococcus pneumoniae (SPn; 45%) and Streptococcus pyogenes (SPy; 37%). 92% of decedents had some prodromal symptoms prior to terminal presentation. The clinical course was often rapid, with 89% found unresponsive, suddenly collapsing, or dying within 24 hours of hospital admission. 64% of deaths were attributed to sepsis, more frequently diagnosed in the SPy group than in the SPn group (71% vs 48%). Pneumonia was found in both SPn and SPy groups, whereas meningitis was exclusively associated with SPn.

CONCLUSION

Our study shows fatal SI is most commonly caused by either SPn or SPy, both of which are frequently associated with prodromal symptoms, rapid terminal clinical course, and evidence of sepsis. Postmortem diagnosis of sepsis is challenging and should be correlated with clinical features, bacterial culture results, and autopsy findings.

Postmortem Study of Cause of Death Among Children Hospitalized With Respiratory Illness in Kenya

BACKGROUND

In resource-limited settings, acute respiratory infections continue to be the leading cause of death in young children. We conducted postmortem investigations in children <5 years hospitalized with a clinical diagnosis of respiratory disease at Kenya's largest referral hospital.

METHODS

We collected respiratory and other tissues postmortem to examine pathologic processes using histology, molecular and immunohistochemistry assays. Nasopharyngeal, trachea, bronchi and lung specimens were tested using 21-target respiratory pathogen real-time reverse transcription polymerase chain reaction assays deployed on Taqman Array Cards. Expert panels reviewed all findings to determine causes of death and associated pathogens.

RESULTS

From 2014 to 2015, we investigated 64 pediatric deaths (median age 7 months). Pneumonia was determined as cause of death in 70% (42/52) of cases where death was associated with an infectious disease process. The main etiologies of pneumonia deaths were respiratory syncytial virus (RSV) (n = 7, 19%), Pneumocystis jirovecii (n = 7, 19%), influenza A (n = 5, 14%) and Streptococcus pneumoniae (n = 5, 14%)-10% of cases had multi-pathogen involvement. Among the other 10 deaths associated with a nonpneumonia infectious process, 4 did not have an etiology assigned, the others were associated with miliary tuberculosis (2), cerebral thrombosis due to HIV (1), Enterobacteriaceae (1), rotavirus (1), and 1 case of respiratory infection with severe hypokalemia associated with RSV.

CONCLUSIONS

In spite of well-established vaccination programs in Kenya, some deaths were still vaccine preventable. Accelerated development of RSV monoclonal antibodies and vaccines, introduction of seasonal influenza vaccination, and maintenance or improved uptake of existing vaccines can contribute to further reductions in childhood mortality.

How often is autopsy contributory in cases of sepsis?

This study sought to determine how often a medico-legal (coronial) autopsy contributes by identifying the source of infection when there has been a clinical diagnosis of sepsis prior to death. Autopsy reports were retrieved in which it was documented there had been a clinical diagnosis of sepsis preceding death. The autopsy report was reviewed to determine if a source for sepsis had been identified. It was found the autopsy was contributory in this respect in less than one fifth of all cases (35 of 198, 18%). It was also determined if there was a post-autopsy diagnosis of sepsis or if sepsis was excluded by a definite alternative diagnosis. During the study, of the 198 cases, sepsis was excluded by an alternative diagnosis in 78 (39%). Thus, the autopsy may be of more application to confirming or excluding a diagnosis of sepsis than identifying a source for sepsis.

Microbiology in minimally invasive autopsy: best techniques to detect infection. ESGFOR (ESCMID study group of forensic and post-mortem microbiology) guidelines

This manuscript aims to: 1) provide specific guidelines on PMM techniques in the setting of minimally invasive autopsy (MIA), both for pathologists collecting samples and for microbiologists advising pathologists and interpreting the results and 2) introduce standardization in PMM sampling at MIA. Post-mortem microbiology (PMM) is crucial to identify the causative organism in deaths due to infection. MIA including the use of post-mortem (PM) computed tomography (CT) and PM magnetic resonance imaging (MRI), is increasingly carried out as a complement or replacement for the traditional PM. In this setting, mirroring the traditional autopsy, PMM aims to: detect infectious organisms causing sudden unexpected deaths; confirm clinically suspected but unproven infection; evaluate the efficacy of antimicrobial therapy; identify emergent pathogens; and recognize medical diagnostic errors. Meaningful interpretation of PMM results requires careful evaluation in the context of the clinical history, macroscopic and microscopic findings. These guidelines were developed by a multidisciplinary team with experts in various fields of microbiology and pathology on behalf of the ESGFOR (ESCMID – European Society of Clinical Microbiology and Infectious Diseases - Study Group of Forensic and Post-mortem Microbiology, in collaboration with the ESP -European Society of Pathology-) based on a literature search and the author’s expertise. Microbiological sampling methods for MIA are presented for various scenarios: adults, children, developed and developing countries. Concordance between MIA and conventional invasive autopsy is substantial for children and adults and moderate for neonates and maternal deaths. Networking and closer collaboration among microbiologists and pathologists is vital to maximize the yield of PMM in MIA.

Severe influenza: overview in critically ill patients

PURPOSE OF REVIEW

Overview of influenza infection, focusing on outcome and complications in critically ill patients. We also discuss relevant elements in immunopathogenesis and their role as predictors of severity.

RECENT FINDINGS

Pandemic influenza A (H1N1) virus circulates seasonally and remains the predominant subtype among intensive care patients. Mortality in acute respiratory failure (ARF) is around 20%, independent of influenza subtypes. During severe infection, the imbalance between pro-inflammatory and anti-inflammatory molecules, such as Th1 and Th17 cytokines, is associated with complicated infections and mortality. Primary viral pneumonia presents in more than 70% of ICU influenza patients and more than 50% develop acute respiratory distress syndrome. Bacterial secondary infection occurs in 20% of severe cases and Streptococcus pneumoniae and Staphylococcus aureus remain the prevalent pathogens. Myocarditis and late-onset cardiovascular complications are associated with mortality. Antiviral therapy within 48 h after onset, avoidance of corticosteroids and rescue therapies for ARF or myocarditis, such as extracorporeal membrane oxygenation, improve survival.

SUMMARY

The present review summarizes current knowledge on pathogenesis and clinical manifestations of severe influenza. Immunological dysfunction during viral infection correlates with severity and mortality among ICU patients. A theranostics strategy should be implemented to improve outcomes.

Printculture of Surgical Pathology and Autopsy Specimens

OBJECTIVES

Printculture is a method of microbiologic assessment previously described for use in the autopsy setting. We sought to compare printculture of surgical and autopsy pathology specimens to standard microbiology culture using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF)-based colony identification.

METHODS

Printculture was performed on 18 frozen samples with corresponding standard culture results. The results of MALDI-TOF identification of colonies recovered by printculture were compared with standard cultures, and percent concordance was calculated.

RESULTS

There was 95.8% concordance to standard culture methods for cases with infections and 100% concordance for cases without infection. The pattern of growth was found to aid in the distinction between contamination and true infection.

CONCLUSIONS

Printculture allows the identification of microorganisms from routinely frozen tissues and provides a bridge between microbiology and histomorphology through the identification of associated histologic features of infection. This technique can be successfully integrated into autopsy and surgical pathology workup of potentially infected tissues.