Clinical Manifestation, mNGS Based Diagnosis and Treatment of Pulmonary Mucormycosis with Rhizopus delemar in a Diabetic Patient

Pulmonary mucormycosis is a severe and often fatal disease that commonly affects patients with underlying conditions, such as diabetes. Early diagnosis and appropriate treatment are crucial for improving survival rates. However, clinical diagnosis remains challenging due to difficulty in obtaining etiological evidence. In this particular case, the patient presented with a cough-producing bloody sputum, and a chest CT revealed lesions in the right upper lobe of the lung. The patient was ultimately diagnosed with pulmonary mucormycosis caused by Rhizopus delemar through clinical bronchoscopy biopsy and metagenomic next-generation sequencing (mNGS) analysis of bronchoalveolar lavage fluid sample. Subsequently, antifungal therapy using the less toxic Amphotericin B cholesterol Organosulfate complex was initiated, improving the patient's condition. In conclusion, our findings underscore the potential of mNGS to provide an accurate and rapid etiological diagnosis of pulmonary mucormycosis, offering a foundation for treatment.

Transcriptomic analysis and carbohydrate metabolism-related enzyme expression across different pH values in Rhizopus delemar

Introduction

pH is one of the important factors affecting the growth and performance of microorganisms.

Methods

We studied the pH response and plant growth-promoting (PGP) ability of Rhizopus delemar using cultivation experiments and transcriptomics, and verified the expression profiles using quantitative real-time PCR.

Results

pH affected the growth and PGP properties of R. delemar. At pH 7, the growth rate of R. delemar was rapid, whereas pH 4 and 8 inhibited mycelial growth and PGP ability, respectively. In the pot experiment, the plant height was the highest at pH 7, 56 cm, and the lowest at pH 4 and pH 5, 46.6 cm and 47 cm, respectively. Enzyme activities were highest at pH 6 to pH 7. Enzyme activities were highest at pH 6 to pH 7. Among the 1,629 differentially expressed genes (DEGs), 1,033 genes were up-regulated and 596 were down-regulated. A total of 1,623 DEGs were annotated to carbohydrate-active enzyme coding genes.

Discussion

The PGP characteristics, e.g., Phosphorus solubilization ability, of R. delemar were strongest at pH 7. The results provide useful information regarding the molecular mechanism of R. delemar pH response.

Identification of lncRNA and weighted gene coexpression network analysis of germinating Rhizopus delemar causing mucormycosis

Rhizopus delemar, an opportunistic fungal pathogen, causes a highly fatal disease, mucormycosis. Spore germination is a crucial mechanism for disease pathogenesis. Thus, exploring the molecular mechanisms of fungal germination would underpin our knowledge of such transformation and, in turn, help control mucormycosis. To gain insight into the developmental process particularly associated with cell wall modification and synthesis, weighted gene co-expression network analysis (WGCNA) was performed including both coding and non-coding transcripts identified in the current study, to find out the module of interest in the germination stages. The module-trait relationship identified a particular module to have a high correlation only at the resting phase and further analysis revealed the module to be enriched for protein phosphorylation, carbohydrate metabolic process, and cellular response to stimulus. Moreover, co-expression network analysis of highly connected nodes revealed cell wall modifying enzymes, especially those involved in mannosylation, chitin-glucan crosslinking, and polygalacturonase activities co-expressing and interacting with the novel lncRNAs among which some of them predicted to be endogenous target mimic (eTM) lncRNAs. Hence, the present study provides an insight into the onset of spore germination and the information on the novel non-coding transcripts with key cell wall-related enzymes as potential targets against mucormycosis.

A case report of brainstem hemorrhage due to Rhizopus delemar-induced encephalitis diagnosed by metagenomic next-generation sequencing (mNGS)

BACKGROUND

Rhizopus delemar is an invasive fungal pathogen that can cause fatal mucormycosis in immunodeficient individuals. Encephalitis caused by R. delemar is rare and difficult to diagnose early. Clinical detection methods for R. delemar include blood fungal culture, direct microscopic examination, and histopathological examination, but the detection is often inadequate for clinical diagnosis and can easily lead to missed diagnosis with delayed treatment.

CASE PRESENTATION

We report a case of a 47-year-old male with brainstem hemorrhage caused by encephalitis due to R. delemar. The patient had a history of hypertension, type 2 diabetes, and irregular medication. No pathogens were detected in cerebrospinal fluid (CSF) and nasopharyngeal secretion cultures. R. delemar was identified by metagenomic next-generation sequencing (mNGS) in CSF, and in combination with the patient's clinical characteristics, encephalitis caused by R. delemar was diagnosed. Antibiotic treatment using amphotericin B liposome in combination with posaconazole was given immediately. However, due to progressive aggravation of the patient's symptoms, he later died due to brainstem hemorrhage after giving up treatment.

CONCLUSIONS

mNGS technique is a potential approach for the early diagnosis of infections, which can help clinicians provide appropriate antibiotic treatments, thus reducing the mortality and disability rate of patients.

Quality improvement of sweet rice wine fermented with Rhizopus delemar on key aroma compounds content, phenolic composition, and antioxidant capacity compared to Rhizopus oryzae

The pure culture fermentation has led to less flavorful rice wine and relatively lower bioactive substance level compared to traditional mixed culture fermentation; however, a pure strain is easily controlled by industrialized producers. The purpose of the present research was to screen a species of Rhizopus for improving the flavor deficiency and antioxidant function of sweet rice wine. Seven rice wine samples fermented with isolated strains were analyzed for their total phenolics, total flavonoids, peptide and antioxidant activity using spectrophotometry, as well as ethanol, ethyl acetate, β-phenethyl alcohol, and volatile alcohol contents measured by headspace gas chromatography (HS-GC), the further principal component analysis determined Rhizopus delemar rice wine better on aroma and antioxidant capacity. A comparison of phenolics profile between R. delemar and R. oryzae rice wines was made based on the measurement data of ultrahigh-performance liquid chromatography coupled with Q-exactive orbitrap mass spectrometry (UHPLC-QE-MS) data. Thirty-two phenolics were identified in sweet rice wine. Overall, the results presented in this study showed that a strain of R. delemar is available for the improvement of flavor and antioxidant activity in sweet rice wine, which has the great potential to be applied to industrialized products.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-021-05250-x.

Targeted Delivery of Antifungal Liposomes to Rhizopus delemar

Mucormycosis (a.k.a. zygomycosis) is an often-life-threatening disease caused by fungi from the ancient fungal division Mucoromycota. Globally, there are nearly a million people with the disease. Rhizopus spp., and R. delemar (R. oryzae, R. arrhizus) in particular, are responsible for most of the diagnosed cases. Pulmonary, rhino-orbito-cerebral, and invasive mucormycosis are most effectively treated with amphotericin B (AmB) and particularly with liposomal formulations (e.g., AmBisome^®). However, even after antifungal therapy, there is still a 50% mortality rate. Hence, there is a critical need to improve therapeutics for mucormycosis. Targeting AmB-loaded liposomes (AmB-LLs) with the pathogen receptor Dectin-1 (DEC1-AmB-LLs) to the beta-glucans expressed on the surface of Aspergillus fumigatus and Candida albicans lowers the effective dose required to kill cells relative to untargeted AmB-LLs. Because Dectin-1 is an immune receptor for R. delemar infections and may bind it directly, we explored the Dectin-1-mediated delivery of liposomal AmB to R. delemar. DEC1-AmB-LLs bound 100- to 1000-fold more efficiently to the exopolysaccharide matrix of R. delemar germlings and mature hyphae relative to AmB-LLs. DEC1-AmB-LLs delivering sub-micromolar concentrations of AmB were an order of magnitude more efficient at inhibiting and/or killing R. delemar than AmB-LLs. Targeted antifungal drug-loaded liposomes have the potential to improve the treatment of mucormycosis.

Selective inhibition of Rhizopus eumelanin biosynthesis by novel natural product scaffold-based designs caused significant inhibition of fungal pathogenesis

Melanin is a dark color pigment biosynthesized naturally in most living organisms. Fungal melanin is a major putative virulence factor of Mucorales fungi that allows intracellular persistence by inducing phagosome maturation arrest. Recently, it has been shown that the black pigments of Rhizopus delemar is of eumelanin type, that requires the involvement of tyrosinase (a copper-dependent enzyme) in its biosynthesis. Herein, we have developed a series of compounds (UOSC-1-14) to selectively target Rhizopus melanin and explored this mechanism therapeutically. The compounds were designed based on the scaffold of the natural product, cuminaldehyde, identified from plant sources and has been shown to develop non-selective inhibition of melanin production. While all synthesized compounds showed significant inhibition of Rhizopus melanin production and limited toxicity to mammalian cells, only four compounds (UOSC-1, 2, 13, and 14) were selected as promising candidates based on their selective inhibition to fungal melanin. The activity of compound UOSC-2 was comparable to the positive control kojic acid. The selected candidates showed significant inhibition of Rhizopus melanin but not human melanin by targeting the fungal tyrosinase, and with an IC50 that are 9 times lower than the reference standard, kojic acid. Furthermore, the produced white spores were phagocytized easily and cleared faster from the lungs of infected immunocompetent mice and from the human macrophages when compared with wild-type spores. Collectively, the results suggested that the newly designed derivatives, particularly UOSC-2 can serve as promising candidate to overcome persistence mechanisms of fungal melanin production and hence make them accessible to host defenses.

Sustainable carbon sources for microbial organic acid production with filamentous fungi

BACKGROUND

The organic acid producer Aspergillus oryzae and Rhizopus delemar are able to convert several alternative carbon sources to malic and fumaric acid. Thus, carbohydrate hydrolysates from lignocellulose separation are likely suitable as substrate for organic acid production with these fungi.

RESULTS

Before lignocellulose hydrolysate fractions were tested as substrates, experiments with several mono- and disaccharides, possibly present in pretreated biomass, were conducted for their suitability for malic acid production with A. oryzae. This includes levoglucosan, glucose, galactose, mannose, arabinose, xylose, ribose, and cellobiose as well as cheap and easy available sugars, e.g., fructose and maltose. A. oryzae is able to convert every sugar investigated to malate, albeit with different yields. Based on the promising results from the pure sugar conversion experiments, fractions of the organosolv process from beechwood (Fagus sylvatica) and Miscanthus giganteus were further analyzed as carbon source for cultivation and fermentation with A. oryzae for malic acid and R. delemar for fumaric acid production. The highest malic acid concentration of 37.9 ± 2.6 g/L could be reached using beechwood cellulose fraction as carbon source in bioreactor fermentation with A. oryzae and 16.2 ± 0.2 g/L fumaric acid with R. delemar.

CONCLUSIONS

We showed in this study that the range of convertible sugars for A. oryzae is even higher than known before. We approved the suitability of fiber/cellulose hydrolysate obtained from the organosolv process as carbon source for A. oryzae in shake flasks as well as in a small-scale bioreactor. The more challenging hemicellulose fraction of F. sylvatica was also positively evaluated for malic acid production with A. oryzae.

Prophylaxis with Isavuconazole or Posaconazole Protects Immunosuppressed Mice from Pulmonary Mucormycosis

We assessed prophylactic or continuous therapy of isavuconazole, posaconazole, or voriconazole in treating pulmonary murine mucormycosis. In the prophylaxis studies, only isavuconazole treatment resulted in significantly improved survival and lowered tissue fungal burden of immunosuppressed mice infected with Rhizopus delemar. In the continuous treatment studies, isavuconazole and posaconazole, but not voriconazole, equally prolonged survival time and lowered tissue fungal burden compared to placebo-treated mice. These results support the use of isavuconazole and posaconazole in prophylaxis treatment.

Comparative proteomics of Rhizopus delemar ATCC 20344 unravels the role of amino acid catabolism in fumarate accumulation

The filamentous fungus Rhizopus delemar naturally accumulates relatively high amounts of fumarate. Although the culture conditions that increase fumarate yields are well established, the network underlying the accumulation of fumarate is not yet fully understood. We set out to increase the knowledge about fumarate accumulation in R. delemar. To this end, we combined a transcriptomics and proteomics approach to identify key metabolic pathways involved in fumarate production in R. delemar, and propose that a substantial part of the fumarate accumulated in R. delemar during nitrogen starvation results from the urea cycle due to amino acid catabolism.