Pathology of infectious diseases: what does the future hold?

Pathologie infectieuse du tube digestif : diagnostics à ne pas manquer

Le contexte récent du COVID-19 a renouvelé l’intérêt des pathologistes pour les maladies d’origine infectieuse. Cet intérêt est d’autant plus fort dans le tube digestif où les symptômes sont aspécifiques, souvent frustres avec un aspect endoscopique normal entraînant parfois une errance diagnostique. Dans ce contexte, les biopsies systématiques réalisées par le clinicien sont parfois le seul moyen de parvenir au diagnostic. Néanmoins, le diagnostic précis de ses pathologies nécessite une bonne connaissance à la fois du contexte de survenue de ces pathologies, de l’aspect histopathologique et d’une analyse rigoureuse utilisant des colorations spéciales et/ou des analyses immunohistochimiques. Certaines pathologies infectieuses du tube digestif sont bien connues par les pathologistes qui sont largement sollicités dans leurs diagnostics (gastrite à Helicobacter pylori, œsophagite à Candida albicans ou la colite à CMV), mais d’autres sont plus délicates à diagnostiquer. Dans cet article, nous présenterons, après avoir rappelé les différentes colorations spéciales utiles, des pathologies bactériennes ou parasitaires rares ou de diagnostic difficile « à ne pas manquer » dans le tube digestif.

`Teaching Infectious Disease Pathology and Taking it To Africa

With the advent of increasing emerging infectious diseases, rising antibiotic resistance, and the growing number of immunocompromised patients, there is increasing demand for infectious disease (ID) pathology expertise and microbiology testing. At present, infectious disease pathology training and emerging molecular microbiology techniques (e.g. metagenomic next-generation sequencing and whole genome sequencing) are not included in most American Council of Graduate Medical Education (ACGME) medical microbiology fellowship curricula, and, not surprisingly, many institutions lack anatomic pathologists with expertise in ID pathology and advanced molecular diagnostics. In this article, we describe the curriculum and structure of the Franz von Lichtenberg Fellowship in Infectious Disease and Molecular Microbiology at Brigham and Women's Hospital in Boston, MA. We emphasize the value of a training model that strives to integrate anatomic pathology, clinical pathology, and molecular pathology by providing examples in a case-based format and presenting selected metrics of the potential impact of such integrative infectious disease pathology service, and briefly describing opportunities and challenges of our global health efforts in Rwanda.

[Histopathological features due to the SARS-CoV-2]

The infection due to the SARS-CoV-2 leads lesions mainly observed at the respiratory tract level, but not exclusively. The analyses of these lesions benefited from different autopsy studies. Thus, these lesions were observed in different organs, tissues and cells. These observations allowed us to rapidly improve the knowledge of the pathophysiological mechanisms associated with this emergent infectious disease. The virus can be detected in formalin fixed paraffin embedded tissues using immunohistochemistry, in situ hybridization, molecular biology and/or electron microscopy approaches. However, many uncertainties are still present concerning the direct role of the SARS-CoV-2 on the different lesions observed in different organs, outside the lung, such as the heart, the brain, the liver, the gastrointestinal tract, the kidney and the skin. In this context, it is pivotal to keep going to increase the different tissue and cellular studies in the COVID-19 positive patients aiming to better understanding the consequences of this new infectious disease, notably considering different epidemiological and co-morbidities associated factors. This could participate to the development of new therapeutic strategies too. The purpose of this review is to describe the main histological and cellular lesions associated with the infection due to the SARS-CoV-2.

[Histological pulmonary features due to the Sars-CoV-2]

The histological lesions associated with an infection with the Sars-CoV-2 are mainly observed at the respiratory tract level, but not exclusively. Analyses of these lesions strongly beneficied from autopsic studies allowing us to improve the knowledge of the pathophysiology mechanisms of this emerging infectious disease. Cytological analyses, notably those obtained from broncho-alveolar lavages, poorly contribute to the Covid-19 diagnosis, but can be usefull for eliminate a couple of differential diagnoses. Although non specific, the lesions observed in the pulmonary parenchyma can be directly associated with the presence of the Sars-CoV-2 thanks to ancillary tools allowing its detection. Indeed, the presence of the virus can be detected using immunohistochemistry, in situ hybridization, molecular biology and/or electron microscopy approaches. Several uncertainties still exist concerning the direct role due to the Sars-CoV-2 in the observed lesions which can be due too to a cardiovascular failure and/or to the treatment(s) received in intensive care units. Thus, it is critical to keep going to increase our efforts for the tissue analyses, notably thanks to the autopsies of Covid-19 patients, in order to better understand the consequences of this infectious disease, and, particularly according the epidemiological factors and the different associated morbidities. An increased knowledge will participate to the further therapeutic strategies against the Covid-19. This review adresses the main histological lesions of the lung parenchyma currently described in patients infected by the Sars-CoV-2.

Biosafety Requirements for Autopsies of Patients with COVID-19: Example of a BSL-3 Autopsy Facility Designed for Highly Pathogenic Agents

Information obtained from autopsies of patients infected with high-risk pathogens is an important pillar in managing a proper response to pandemics, particular in the early phase. This is due to the fact that autopsy allows efficient evaluation of comorbidities for risk assessment, as well as identification of key pathophysiological and molecular mechanisms in organs driving the severity of disease which might be important targets for therapeutic interventions. In the case of patients who have died of infection with unknown pathogens, isolation and culture of pathogens from the affected organs is another important opportunity for a proper response to (re)emerging infectious diseases. However, the situation of COVID-19 demonstrated that there were concerns about performing autopsies because of biosafety risks. In this review we compare requirements for biosafety level 3 (BSL-3) laboratories from the European Commission and the World Health Organization and summarize specific recommendations for postmortem analysis of COVID-19-deceased patients from the Centers for Disease Control and Prevention. Furthermore, we describe in detail a BSL-3 facility with enhanced protection of personnel and an environment that has been designed for performing autopsies, biobanking of collected tissue specimens, and culture of pathogens in cases of high-risk pathogen infections and report on the experience obtained in operating this facility in the context of COVID-19.

Clinical and molecular practice of European thoracic pathology laboratories during the COVID-19 pandemic. The past and the near future

Background

This study evaluated the consequences in Europe of the COVID-19 outbreak on pathology laboratories orientated toward the diagnosis of thoracic diseases.

Materials and methods

A survey was sent to 71 pathology laboratories from 21 European countries. The questionnaire requested information concerning the organization of biosafety, the clinical and molecular pathology, the biobanking, the workload, the associated research into COVID-19, and the organization of education and training during the COVID-19 crisis, from 15 March to 31 May 2020, compared with the same period in 2019.

Results

Questionnaires were returned from 53/71 (75%) laboratories from 18 European countries. The biosafety procedures were heterogeneous. The workload in clinical and molecular pathology decreased dramatically by 31% (range, 3%-55%) and 26% (range, 7%-62%), respectively. According to the professional category, between 28% and 41% of the staff members were not present in the laboratories but did teleworking. A total of 70% of the laboratories developed virtual meetings for the training of residents and junior pathologists. During the period of study, none of the staff members with confirmed COVID-19 became infected as a result of handling samples.

Conclusions

The COVID-19 pandemic has had a strong impact on most of the European pathology laboratories included in this study. Urgent implementation of several changes to the organization of most of these laboratories, notably to better harmonize biosafety procedures, was noted at the onset of the pandemic and maintained in the event of a new wave of infection occurring in Europe.

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Biosafety measures used in the first wave of the COVID-19 crisis were heterogeneous in 53 European pathology laboratories.

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A dramatic decrease of the workload in pathology laboratories was noted.

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No case of healthcare workers contaminated with SARS-CoV-2 associated with samples handling was identified.

Utility of an infectious and tropical disease histopathology diagnostic review service

AIM

To assess the utility of a London-based infectious and tropical disease histopathology diagnostic review service.

METHODS

The original and specialist review histopathology reports of 457 samples from over 3 years of referrals were compared retrospectively.

RESULTS

Overall 329 (72.0%) showed no significant difference; 34 (7.4%) showed a non-clinically significant difference; and 94 (20.6%) showed a clinically significant difference. Of the 94 clinically significant discrepancies, 46 (48.9%) were incorrectly suspected infections; 19 (20.2%) were missed infections; 8 (8.5%) were different infections; and in 20 (21.3%), the specialist review yielded more specific identification of an organism or a more correct assessment of its viability.

CONCLUSIONS

A review of histopathology cases by an infectious disease (ID) histopathology referral centre has yielded a 20.6% clinically significant error rate. Measures to improve training in ID histopathology in the UK are discussed.

Acute Viral Hepatitis: Beyond A, B, and C

From the standpoint of the surgical pathologist "hepatitis" is defined as the set of histologic patterns of lesions found in livers infected by hepatotropic viruses, by non-hepatotrophic viruses leading to liver inflammation in the context of systemic infection, or due to an autoimmune disease, drug, or toxin involving the liver. This article is centered on the histologic patterns of injury in acute viral hepatitis, encompassing the hepatotropic viruses A, B, C, D, and E and the "icteric hemorrhagic fevers" (dengue, hantavirus, yellow fever). A brief mention of viruses causing hepatitis in immunosuppressed patients also is presented.

[Practices in infectious pathology in France in 2015. Results of the national survey]

Pathologists have been, are and will be always implicated in the diagnosis of infectious and tropical diseases. The resurgence of opportunistic infections due to the development of immunosuppressive drugs, the increase of migratory involvements draining tropical infections and the last epidemics spotlight the importance of pathologists in the field of infectious diseases. However, cancer is nowadays the first preoccupation of pathologists, which is constantly subject to evaluate diagnostic and prognostic markers and factors predictive to targeted therapy response or immunotherapy. As tumor pathology, infectious diseases require more sophisticated and rapidly changing complementary techniques, appraisals and perhaps a national network of diagnosis. The infectious pathology club committee carries out here a census of methods used in the diagnosis of infectious diseases in France in 2015 and particularly the different techniques used by laboratories to perform infectious diseases diagnosis. This will lay down the foundation of a future national organization of the infectious pathology in providing efficient services (diagnostic support, complementary tools) for the community of French pathologists in this specific domain of competence.