Comparison of serum PCR assay and histopathology for the diagnosis of invasive aspergillosis and mucormycosis in immunocompromised patients with sinus involvement

Epidemiology, Modern Diagnostics, and the Management of Mucorales Infections

Mucormycosis is an uncommon, yet deadly invasive fungal infection caused by the Mucorales moulds. These pathogens are a WHO-assigned high-priority pathogen group, as mucormycosis incidence is increasing, and there is unacceptably high mortality with current antifungal therapies. Current diagnostic methods have inadequate sensitivity and specificity and may have issues with accessibility or turnaround time. Patients with diabetes mellitus and immune compromise are predisposed to infection with these environmental fungi, but COVID-19 has established itself as a new risk factor. Mucorales also cause healthcare-associated outbreaks, and clusters associated with natural disasters have also been identified. Robust epidemiological surveillance into burden of disease, at-risk populations, and emerging pathogens is required. Emerging serological and molecular techniques may offer a faster route to diagnosis, while newly developed antifungal agents show promise in preliminary studies. Equitable access to these emerging diagnostic techniques and antifungal therapies will be key in identifying and treating mucormycosis, as delayed initiation of therapy is associated with higher mortality.

Microbiological and Molecular Diagnosis of Mucormycosis: From Old to New

Members of the order Mucorales may cause severe invasive fungal infections (mucormycosis) in immune-compromised and otherwise ill patients. Diagnosis of Mucorales infections and discrimination from other filamentous fungi are crucial for correct management. Here, we present an overview of current state-of-the-art mucormycosis diagnoses, with a focus on recent developments in the molecular field. Classical diagnostic methods comprise histology/microscopy as well as culture and are still the gold standard. Newer molecular methods are evolving quickly and display great potential in early diagnosis, although standardization is still missing. Among them, quantitative PCR assays with or without melt curve analysis are most widely used to detect fungal DNA in clinical samples. Depending on the respective assay, sequencing of the resulting PCR product can be necessary for genus or even species identification. Further, DNA-based methods include microarrays and PCR-ESI-MS. However, general laboratory standards are still in development, meaning that molecular methods are currently limited to add-on analytics to culture and microscopy.

Diagnostic performance of real-time polymerase chain reaction assay on blood for invasive aspergillosis and mucormycosis

OBJECTIVES

This study aimed to evaluate the diagnostic usefulness of real-time (RT) polymerase chain reaction (PCR) on blood samples for diagnosis of invasive aspergillosis and mucormycosis in patients with suspected invasive mould infection.

METHODS

Adult patients with suspected invasive mould infection were prospectively enrolled at a tertiary referral hospital in Seoul, South Korea between 2017 and 2020. Standard tests for diagnosis of invasive mould infection and RT-PCR for Aspergillus, Mucor and Rhizopus using blood samples were performed. We evaluated the diagnostic performance of RT-PCR tests in patients diagnosed with proven and probable invasive aspergillosis or mucormycosis infection, according to the modified definitions of the EORTC/MSG 2019.

RESULTS

A total of 102 patients with suspected invasive mould infection were enrolled. Of these patients, 46 (45%) were classified as having proven (n = 13) or probable (n = 33) invasive aspergillosis, 21 (21%) as proven (n = 17) or probable (n = 4) invasive mucormycosis and 18 (18%) as possible invasive mould infection. The remaining 13 (13%) were classified as not having invasive mould infection. Patients with possible invasive mould infection (n = 18) and coinfection of aspergillosis and mucormycosis (n = 4) were excluded from the final analysis. The sensitivity and specificity of the Aspergillus PCR were 54.3% ([25/46], 95% confidence interval [CI]: 40.2-67.9%) and 94.1% ([32/34], 95% CI: 80.9-98.4%), respectively. The sensitivity and specificity of the Mucor or Rhizopus PCR were 57.1% ([12/21], 95% CI: 36.6-75.5%) and 76.3% ([45/59], 95% CI: 64.0-85.3), respectively.

CONCLUSIONS

Our study suggests that blood PCR can be a useful adjunct test for diagnosing patients with suspected invasive mould infection.

A comparison of histomorphologic diagnosis with culture- and immunohistochemistry-based diagnosis of invasive aspergillosis and mucormycosis

Background: Due to the low sensitivity of mould culture, clinicians usually depend on the histomorphologic diagnosis of invasive mould infection for empirical antifungal therapy. However, definite diagnosis is not always possible based on the mould morphology. We thus compared the histomorphologic diagnosis with immunohistochemistry (IHC)- and culture-based diagnosis.Methods: All adult patients who underwent tissue biopsy and in whom the histomorphologic diagnosis revealed invasive mould infection were enrolled at a tertiary hospital, Seoul, South Korea, between 1992 and 2014 (retrospectively) and 2015 and 2019 (prospectively). Their histomorphologic diagnoses were classified as two categories: (1) acute-angled branching, septate hyphae with parallel walls and a uniform width ('morphologic aspergillosis') and (2) right-angled branching pauciseptate, broader and ribbon-like hyphae with nonparallel walls ('morphologic mucormycosis').Results: A total of 113 patients were finally analysed and their histomorphologic diagnoses were classified as follows: 51 (45%) with morphologic aspergillosis, 62 (55%) with morphologic mucormycosis. Of the 51 patients with morphologic aspergillosis, 46 (90%) received the same diagnosis based on culture and/or IHC, and the remaining five (10%) gave positive IHC result for mucormycosis. Of the 62 patients with morphologic mucormycosis, 60 (97%) had the same diagnosis based on culture and/or IHC, and the remaining two (3%) yielded a positive aspergillus culture or a positive IHC result for aspergillosis, respectively.Conclusions: The majority of histomorphologic diagnoses appear to be consistent with definitive diagnoses based on sterile culture and IHC tests. However, about 10% of 'morphologic aspergillosis' diagnoses were mucormycosis cases.

Recent advances in the molecular diagnosis of mucormycosis

INTRODUCTION

Fungal infection burden related to Mucorales has been on the rise with significant associated morbidity and mortality. The major obstacle in the management has been lack of a non-invasive rapid and a reliable diagnostic test. Developing a culture-independent biomarker for the early diagnosis of mucormycosis is a major unmet need in modern mycology. Several approaches have been developed, such as immunohistochemistry (IHC) that can confirm the histopathologic diagnosis of the invasive mold infection, polymerase chain reaction (PCR) on formalin-fixed paraffin-embedded (FFPE) or fresh tissue, body fluids such as bronchoalveolar fluid (BAL), and detection directly from serum/blood. Serologic tests, matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS), metabolomics and metagenomic shotgun sequencing are other evolving technologies. Area covered: In this review paper, we report the current status of the molecular diagnostics in the diagnosis of mucormycosis: serologic tests, IHC, PCR, protein-based with MALDI-TOF, metabolomics and metagenomic sequencing. Expert commentary: This review will conclude with an expert commentary on the potential uses/challenges of the currently available tests and the future of molecular diagnostics for mucormycosis.

Identification of fungal causative agents of rhinosinusitis from Mashhad, Iran

Background and Purpose:

Rhinosinusitis is a common disorder, influencing approximately 20% of the population at some time of their lives. It was recognized and reported with expanding recurrence over the past two decades worldwide. Undoubtedly, correct diagnosis of fungi in patients with fungal rhinosinusitis affects the treatment planning and prognosis of the patients. Identification of the causative agents using the standard mycological procedures remains difficult and time-consuming.

Materials and Methods:

Based on clinical and radiological parameters, 106 patients suspected of fungal rhinosinusitis were investigated in this cross-sectional prospective study from April 2012 to March 2016 at an otorhinolaryngology department. In this study, internal transcribed spacer (ITS) and calmodulin (CaM) sequencing were respectively validated as reliable techniques for the identification of Mucorales and Aspergillus to species level (both agents of fungal rhinosinusitis).

Results:

Of these, 63 (59.4%) patients were suspected of allergic fungal rhinosinusitis (AFRS), 40 (37.7%) patients suspected of acute invasive fungal rhinosinusitis (AIFRS), and 3 (2.8%) patients suspected of mycetoma. In patients suspected of AFRS, AIFRS, and mycetoma only 7, 29, and 1 had positive fungal culture, respectively. After ITS and CaM sequencing, Aspergillus flavus was the most common species isolated from non-invasive forms, and A. flavus and Rhizopus oryzae were more frequently isolated from invasive forms.

Conclusion:

Aspergillus flavus is the most common agent of fungal rhinosinusitis in Iran, unlike most other reports from throughout the world stating that A. fumigatus is the most frequent causative agent of this disease.