The Use of Whole Genome and Next-Generation Sequencing in the Diagnosis of Invasive Fungal Disease

Diagnosis and management of invasive fungal diseases by next-generation sequencing: are we there yet?

INTRODUCTION

Invasive fungal diseases (IFDs) are a serious threat to immunocompromised patients. Routine diagnostic methods have limited performance in identifying IFDs. Next-generation sequencing (NGS), including metagenomic NGS (mNGS) and whole-genome sequencing (WGS), recently emerged as diagnostic methods that could provide more accurate and timely diagnoses and management of IFDs.

AREAS COVERED

This article describes the emergence of NGS as a diagnostic tool to address the limitations of current tests. The literature regarding its application and clinical utility in the diagnosis of IFDs is reviewed. Practical considerations, challenges, and opportunities as they relate to the development and implementation of mNGS and WGS for fungal pathogens are discussed.

EXPERT OPINION

NGS emerged over a decade ago with the potential to solve many of the challenges in diagnosing infectious diseases, including IFDs. However, published literature has yielded conflicting data about its clinical utility. The increased clinical adoption of NGS is improving our understanding of how to interpret and use its results to guide actionable decisions. Still, several gaps remain. As the cost, effort, and expertise involved in performing NGS decrease and the reporting of its results becomes standardized, NGS is poised to fill current gaps in the diagnosis of IFDs.

COVID-19 in pulmonary critically ill patients: metagenomic identification of fungi and characterization of pathogenic microorganisms

Background

Fungal co-infection is prevalent in critically ill patients with COVID-19. The conventional approach applied to fungal identification has relatively low sensitivity and is time-consuming. The metagenomic next-generation sequencing (mNGS) technology can simultaneously detect a variety of microorganisms, and is increasingly being used for the rapid detection and diagnosis of pathogens.

Methods

In this single-center retrospective study, we described the clinical presentation and outcomes of COVID-19 and mNGS positive for fungi in pulmonary critically ill patients during the outbreak of Omicron infection from December 2022 to January 2023.

Results

Among 43 COVID-19 patients with acute respiratory distress syndrome (ARDS) on a single intensive care unit (ICU), 10 were reported to be fungal positive using the mNGS test. The number of pathogenic microorganisms detected by mNGS was significantly higher than that via traditional methods, especially in the detection of fungi and viruses. Aspergillus infection was dominant, and most of these patients also had concurrent bacterial or viral infections. Probable or possible COVID-19-associated pulmonary aspergillosis (CAPA) was diagnosed in all 10 patients, and the prognosis was poor.

Conclusion

Patients with COVID-19 may be at increased risk of developing fungal infections as well as concurrent bacterial or viral infections, and mNGS can be a powerful tool in identifying these infections. Clinicians should be aware of the increased risk of fungal infections in COVID-19 patients, particularly those who have underlying immunocompromising conditions, and should monitor for early signs of infection.

Molecular Markers: An Overview of Data Published for Fungi over the Last Ten Years

Fungi are amongst the most abundant and diverse organisms. Despite being widely known for their adverse role in food spoilage or as pathogens for humans, animals, or plants, they also present several beneficial effects. Fungi contribute to human well-being due to their role as decomposers, degrading decay matter into smaller molecules which can be easily used by other ecosystem members. These organisms can produce medicinal compounds or modulate protective immune responses in human intestine. Fungi intervene in diverse food processes or act as a food supply. Due to fungal diversity, the unequivocal identification of these organisms is crucial to increasing their practical applications and decreasing their adverse effects. The process of identification could be achieved through the integral sequencing of fungi genomes. However, this procedure would be time-consuming and rather cost-inefficient. Therefore, several molecular markers have been developed to overcome these limitations. The chronology of DNA-based molecular markers development can be divided into three main steps: (1) prior to the development of the PCR technique (RFLP); (2) after the development of the PCR technique (RAPD, AFLP, ISSR, VNTR, SNP, InDels, and DNA barcoding); (3) after the development of the massive parallel sequencing technique (Metabarcoding and WGS). Therefore, the present review covers an overview of the most recently developed molecular markers used for fungal detection and identification.