Rapid Diagnosis of Central Nervous System Scedosporiosis by Specific Quantitative Polymerase Chain Reaction Applied to Formalin-Fixed, Paraffin-Embedded Tissue.

Robert J Lauerer,Katharina Feil,Rudi Beschorner,Ulf Ziemann,Georgios Naros,Annerose Mengel,Jennifer Sartor-Pfeiffer,Katharina Berger,Emely Rosenow,Johann-Martin Hempel,Anna Hofmann,Volker Rickerts

doi:10.3390/jof8010019

Abstract

Scedosporium (S.) apiospermum is a typical mold causing cerebral abscesses, often after near-drowning. Infections are associated with high morbidity and mortality due to diagnostic challenges including the need for prolonged incubation of cultures. In addition, histopathological differentiation from other filamentous fungi, including Aspergillus fumigatus, may not be possible, excluding early specific diagnosis and targeted therapy. Polymerase chain reaction (PCR) on tissue samples can rapidly identify fungi, leading to an earlier adequate treatment. Due to an extensive spectrum of causative fungi, broad-range PCRs with amplicon sequencing have been endorsed as the best DNA amplification strategy. We herein describe a case with brain abscesses due to S. apiospermum in a 66-year-old immunocompromised female patient. While broad-range PCR failed to identify a fungal pathogen from a cerebral biopsy demonstrating hyaline mold hyphae, specific quantitative PCR (qPCR) identified Scedosporium and ruled out Aspergillus, the most prevalent agent of central nervous system mold infection. A panel of specific qPCR assays, guided by the morphology of fungal elements in tissue or as a multiplex assay, may be a successful molecular approach to identify fungal agents of brain abscesses. This also applies in the presence of negative broad-range fungal PCR, therefore providing diagnostic and therapeutic potential for early specific management and improvement of patient clinical outcome.

Highlights

An intracerebral brain abscess is a dynamic form of intracranial central nervous system (CNS) infection, defined as a local infection of the brain slowly developing into an encapsulated collection of pus with a connective tissue capsule presenting a mass-like lesion [1].The growing use of immunosuppressive therapies and organ transplantation have caused an increase in the incidence of cerebral fungal infections
Genus-specific quantitative PCR (qPCR) assays from the brain tissue provided a fast diagnosis of scedosporiosis
QPCR assays ruled out the presence of the most common mold causing hyalohyphomycosis, A. fumigatus, providing a basis for rapid, specific patient management

Summary

Introduction

An intracerebral brain abscess is a dynamic form of intracranial central nervous system (CNS) infection, defined as a local infection of the brain slowly developing into an encapsulated collection of pus with a connective tissue capsule presenting a mass-like lesion [1]. Diagnosis of brain abscesses caused by S. apiospermum is difficult due to the slow growth of this mold and non-specific tissue morphology, demonstrating hyaline hyphae. This may impair specific management, leading to high mortality of up to 74% [6,7,8]. Given the scarcity of fungal elements in brain biopsies, the histological discrimination to more common pathogenic fungi such as Aspergillus spp. is impaired, and the diagnosis of scedosporiosis has mostly been based on fungal culture, often delaying proper treatment of infected patients [9,14]. FFPE was non-diagnostic, but DNA amplification confirmed scedosporiosis and ruled out aspergillosis by the application of two specific qPCR assays on FFPE tissue samples of the cerebral abscess showing hyaline hyphae

Case Presentation

Materials and Methods

Discussion

Findings

Literature