Molecular identification and biological characteristic analysis of an Apiotrichum mycotoxinivorans (formerly Trichosporon mycotoxinivorans) strain isolated from sputum specimens of a pediatric patient with pneumonia

Effects of Long-Term Heavy Metal Exposure on the Species Diversity, Functional Diversity, and Network Structure of Oral Mycobiome

Oral fungal homeostasis is closely related to the state of human health, and its composition is influenced by various factors. At present, the effects of long-term soil heavy metal exposure on the oral fungi of local populations have not been adequately studied. In this study, we used inductively coupled plasma-mass spectrometry (ICP-MS) to detect heavy metals in agricultural soils from two areas in Gansu Province, northwestern China. ITS amplicon sequencing was used to analyze the community composition of oral buccal mucosa fungi from local village residents. Simultaneously, the functional annotation of fungi was performed using FUNGuild, and co-occurrence networks were constructed to analyze the interactions of different functional fungi. The results showed that the species diversity of the oral fungi of local populations in the soil heavy metal exposure group was lower than that of the control population. The relative abundance of Apiotrichum and Cutaneotrichosporon was higher in the exposure group than in the control group. In addition, Cutaneotrichosporon is an Animal Pathogen, which may lead to an increased probability of disease in the exposure group. Meanwhile, there were significant differences in the co-occurrence network structure between the two groups. The control group had a larger and more stable network than the exposure group. Eight keystone taxa were observed in the network of the control group, while none were observed in that of the exposure group. In conclusion, heavy metal exposure may increase the risk of diseases associated with Apiotrichum and Cutaneotrichosporon infection in the local populations. It can also lead to the loss of keystone taxa and the reduced stability of the oral fungal network. The above results illustrated that heavy metal exposure impairs oral fungal interactions in the population. This study extends our understanding of the biodiversity of oral fungi in the population and provides new insights for further studies on the factors influencing oral fungal homeostasis.

Comparative Genomic Analysis of an Apiotrichum cacaoliposimilis Strain Isolated from a Patient with Urinary Tract Infection

Opportunistic infections caused by fungi, particularly those occurring in immunocompromised patients, are considered challenging worldwide. Therefore, a comprehensive understanding of pathogenic fungi is necessary. The present study reports the isolation of a strain of Apiotrichum cacaoliposimilis, which is difficult to detect using conventional clinical assays, from the sterile urine samples of a patient with a urinary tract infection. Sanger sequencing of the internal transcribed spacer regions confirmed the genus of the microbe, while whole-genome sequencing yielded the initial genome assembly of A. cacaoliposimilis. A total of 7,161 predicted proteincoding genes were mapped using multiple databases, including Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, non-redundant protein database, Pathogen-Host Interactions Database, and Comprehensive Antibiotic Resistance Database. The phenotypic data, biochemical reactions, and antimicrobial susceptibility analyses were conducted to reveal the metabolic properties, virulence, and drug resistance profile of the isolated A. cacaoliposimilis. The rank-sum test revealed the differences in the intergeneric distribution of the highly virulent genes UgeB and Pem2. In addition, other genes exhibited significant overlap in terms of virulence factors with the clinical isolate Apiotrichum mycotoxinivorans GMU1709. Fortunately, similar to most fungi belonging to the Apiotrichum genus, the isolate investigated in the present study was also sensitive to the drug voriconazole (MIC = 0.06 μg/ml). In summary, the phylogenetic placement, potential pathogenic genes, drug sensitivity patterns, and morphological characteristics of the isolated A. cacaoliposimilis were determined precisely in the present study.

The first report of Apiotrichum mycotoxinivorans isolation from human cerebrospinal fluid

Fungal infections due to Apiotrichum mycotoxinivorans are clinically rare. Here, we report a case of invasive blood and cerebrospinal fluid infection by Apiotrichum mycotoxinivorans in a girl with B-cell acute lymphoblastic leukemia. This is the first report of the isolation of Apiotrichum mycotoxinivorans from human cerebrospinal fluid. MRI features of meningitis caused by this fungus are presented. Three small isoquinoline alkaloids inhibited the growth of this rare fungus in vitro, providing a starting point for the application of natural products to treat this highly fatal fungal infection. Our case presentation confirms Apiotrichum mycotoxinivorans as a potential emerging pathogen in patients with hematological malignancy undergoing chemotherapy.

The first two mitochondrial genomes from Apiotrichum reveal mitochondrial evolution and different taxonomic assignment of Trichosporonales

Apiotrichum is a diverse anamorphic basidiomycetous yeast genus, and its mitogenome characterization has not been revealed. In this study, we assembled two Apiotrichum mitogenomes and compared them with mitogenomes from Agaricomycotina, Pucciniomycotina and Ustilaginomycotina. The mitogenomes of Apiotrichum gracile and A. gamsii comprised circular DNA molecules, with sizes of 34,648 bp and 38,096 bp, respectively. Intronic regions were found contributed the most to the size expansion of A. gamsii mitogenome. Comparative mitogenomic analysis revealed that 6.85-38.89% of nucleotides varied between tRNAs shared by the two Apiotrichum mitogenomes. The GC content of all core PCGs in A. gamsii was lower than that of A. gracile, with an average low value of 4.97%. The rps3 gene differentiated the most among Agaricomycotina, Pucciniomycotina and Ustilaginomycotina species, while nad4L gene was the most conserved in evolution. The Ka/Ks values for cob and rps3 genes were > 1, indicating the two genes may be subjected to positive selection in Agaricomycotina, Pucciniomycotina and Ustilaginomycotina. Frequent intron loss/gain events and potential intron transfer events have been detected in evolution of Agaricomycotina, Pucciniomycotina and Ustilaginomycotina. We further detected large-scale gene rearrangements between the 19 mitogenomes from Agaricomycotina, Pucciniomycotina and Ustilaginomycotina, and fifteen of the 17 mitochondrial genes shared by Apiotrichum varied in gene arrangements. Phylogenetic analyses based on maximum likelihood and Bayesian inference methods using a combined mitochondrial gene dataset revealed different taxonomic assignment of two Apiotrichum species, wherein A. gamsii had a more closely relationship with Trichosporon asahii. This study served as the first report on mitogenomes from the genus Apiotrichum, which promotes the understanding of evolution, genomics, and phylogeny of Apiotrichum.

Transcriptome analysis reveals gene expression changes of the basidiomycetous yeast Apiotrichum mycotoxinivorans in response to ochratoxin A exposure

Ochratoxin A (OTA) is one of the most common and deleterious mycotoxins found in food and feedstuffs worldwide; however, Apiotrichum mycotoxinivorans can detoxify OTA. Our results show that A. mycotoxinivorans GUM1709 efficiently degraded OTA, but it caused the accumulation of intracellular reactive oxygen species. The main aim of this study was to identify potential OTA-detoxifying enzymes and to explore the effects of OTA on A. mycotoxinivorans GMU1709. RNA-seq data revealed that 1643 and 1980 genes were significantly upregulated and downregulated, respectively, after OTA exposure. Functional enrichment analyses indicated that OTA exposure enhanced defense capability, protein transport, endocytosis, and energy metabolism; caused ribosomal stress; suppressed DNA replication and transcription; inhibited cell growth and division; and promoted cell death. The integration of secretome, gene expression, and molecular docking analyses revealed that two carboxypeptidase homologues (members of the metallocarboxypeptidase family) were most likely responsible for the detoxification of both extracellular and intracellular OTA. Superoxide dismutase and catalase were the main genes activated in response to oxidative stress. In addition, analysis of key genes associated with cell division and apoptosis showed that OTA exposure inhibited mitosis and promoted cell death. This study revealed the possible OTA response and detoxification mechanisms in A. mycotoxinivorans.

Bronchial Artery-Pulmonary Artery Shunt by Apiotrichum mycotoxinivorans Infection in a Recurrent Hemoptysis Case

Background

Apiotrichum mycotoxinivorans is a rare mycotoxinivorans, and its pathogenicity is unknown. Bronchial artery shunt is a pathophysiological state following congenital or acquired chronic infection. We report a rare case of bronchial artery shunt by A. mycotoxinivorans infection in a recurrent hemoptysis patient.

Case Presentation

A 45-year-old female presented with recurrent cough and hemoptysis for 4 years. Before admission, she had been treated in several hospitals for pulmonary tuberculosis and bronchiectasis and received standardized anti-tuberculosis treatment for 1 year, but it was ineffective. After admission, CTPA and bronchial arterial angiography showed left bronchial artery–left pulmonary artery shunt and right bronchial artery–right pulmonary artery shunt. Fiber-optic bronchoscopy was performed, which revealed a large amount of purulent secretions, bronchoalveolar lavage fluid fungi (1-3)-β-d glucan: 728.06, and GM test: 3.239. Fungal hyphae and spores were observed by gram staining of BALF smear. Acid-fast bacilli were not found in BALF smear and brush smear. Two consecutive BALF fungal cultures grew A. mycotoxinivorans, the identity of which was confirmed by internal-transcribed-spacer (ITS) sequencing. Intravenous amphotericin B liposome (30mg; 0.5mg/kg, QD) was given for 2 weeks, embolization was performed, and itraconazole (voriconazole allergy) was taken orally for 9 months after operation. Hemoptysis and pulmonary lesions gradually improved after treatment.

Conclusion

We report the first case of bronchial artery–pulmonary artery shunt in a patient diagnosed with A. mycotoxinivorans infection. Phagocytosis of fungi by leukocytes was observed, and the pathogenicity of the fungus was confirmed in order to heighten the awareness of these infections.

Transcriptomic responses of the zearalenone (ZEN)-detoxifying yeast Apiotrichum mycotoxinivorans to ZEN exposure

Zearalenone (ZEN) is a potent oestrogenic mycotoxin that is mainly produced by Fusarium species and is a serious environmental pollutant in animal feeds. Apiotrichum mycotoxinivorans has been widely used as a feed additive to detoxify ZEN. However, the effects of ZEN on A. mycotoxinivorans and its detoxification mechanisms remain unclear. In this study, transcriptomic and bioinformatic analyses were used to investigate the molecular responses of A. mycotoxinivorans to ZEN exposure and the genetic basis of ZEN detoxification. We detected 1424 significantly differentially expressed genes (DEGs), of which 446 were upregulated and 978 were downregulated. Functional and enrichment analyses showed that ZEN-induced genes were significantly associated with xenobiotic metabolism, oxidative stress response, and active transport systems. However, ZEN-inhibited genes were mainly related to cell division, cell cycle, and fungal development. Subsequently, bioinformatic analysis identified candidate ZEN-detoxification enzymes. The Baeyer-Villiger monooxygenases and carboxylesterases, which are responsible for the formation and subsequent hydrolysis of a new ZEN lactone, respectively, were significantly upregulated. In addition, the expression levels of genes related to conjugation and transport involved in the xenobiotic detoxification pathway were significantly upregulated. Moreover, the expression levels of genes encoding enzymatic antioxidants and those related to growth and apoptosis were significantly upregulated and downregulated, respectively, which made it possible for A. mycotoxinivorans to survive in a highly toxic environment and efficiently detoxify ZEN. This is the first systematic report of ZEN tolerance and detoxification in A. mycotoxinivorans. We identified the metabolic enzymes that were potentially involved in detoxifying ZEN in the GMU1709 strain and found that ZEN-induced transcriptional regulation of genes is key to withstanding highly toxic environments. Hence, our results provide valuable information for developing enzymatic detoxification systems or engineering this detoxification pathway in other species.

Complete Genome Sequencing and Comparative Analysis of the Clinically-Derived Apiotrichum mycotoxinivorans Strain GMU1709

Over the past decade, Apiotrichum mycotoxinivorans has been recognized globally as a source of opportunistic infections. It is a yeast-like fungus, and its association as an uncommon pulmonary pathogen with cystic fibrosis patients has been previously reported. Immunocompromised patients are at the highest risk of A. mycotoxinivorans infections. Therefore, to investigate the genetic basis for the pathogenicity of A. mycotoxinivorans, we performed whole-genome sequencing and comparative genomic analysis of A. mycotoxinivorans GMU1709 that was isolated from sputum specimens of a pneumonia patient receiving cardiac repair surgery. The assembly of Oxford Nanopore reads from the GMU1709 strain and its subsequent correction using Illumina paired-end reads yielded a high-quality complete genome with a genome size of 30.5 Mb in length, which comprised six chromosomes and one mitochondrion. Subsequently, 8,066 protein-coding genes were predicted based on multiple pieces of evidence, including transcriptomes. Phylogenomic analysis indicated that A. mycotoxinivorans exhibited the closest evolutionary affinity to A. veenhuisii, and both the A. mycotoxinivorans strains and the formerly Trichosporon cutaneum ACCC 20271 strain occupied the same phylogenetic position. Further comparative analysis supported that the ACCC 20271 strain belonged to A. mycotoxinivorans. Comparisons of three A. mycotoxinivorans strains indicated that the differences between clinical and non-clinical strains in pathogenicity and drug resistance may be little or none. Based on the comparisons with strains of other species in the Trichosporonaceae family, we identified potential key genetic factors associated with A. mycotoxinivorans infection or pathogenicity. In addition, we also deduced that A. mycotoxinivorans had great potential to inactivate some antibiotics (e.g., tetracycline), which may affect the efficacy of these drugs in co-infection. In general, our analyses provide a better understanding of the classification and phylogeny of the Trichosporonaceae family, uncover the underlying genetic basis of A. mycotoxinivorans infections and associated drug resistance, and provide clues into potential targets for further research and the therapeutic intervention of infections.

Multidrug-resistant Trichosporon species: underestimated fungal pathogens posing imminent threats in clinical settings

Species of Trichosporon and related genera are widely used in biotechnology and, hence, many species have their genome sequenced. Importantly, yeasts of the genus Trichosporon have been increasingly identified as a cause of life-threatening invasive trichosporonosis (IT) in humans and are associated with an exceptionally high mortality rate. Trichosporon spp. are intrinsically resistant to frontline antifungal agents, which accounts for numerous reports of therapeutic failure when echinocandins are used to treat IT. Moreover, these fungi have low sensitivity to polyenes and azoles and, therefore, are potentially regarded as multidrug-resistant pathogens. However, despite the clinical importance of Trichosporon spp., our understanding of their antifungal resistance mechanisms is quite limited. Furthermore, antifungal susceptibility testing is not standardized, and there is a lack of interpretive epidemiological cut-off values for minimal inhibitory concentrations to distinguish non-wild type Trichosporon isolates. The route of infection remains obscure and detailed clinical and environmental studies are required to determine whether the Trichosporon infections are endogenous or exogenous in nature. Although our knowledge on effective IT treatments is rather limited and future randomized clinical trials are required to identify the best antifungal agent, the current paradigm advocates the use of voriconazole, removal of central venous catheters and recovery from neutropenia.

Molecular Identification, Genotyping, Phenotyping, and Antifungal Susceptibilities of Medically Important Trichosporon, Apiotrichum, and Cutaneotrichosporon Species

Recently, Trichosporon taxonomy has been reevaluated and new genera of the Trichosporonaceae family have been described. Here, 26 clinical isolates were submitted for identification via sequencing of the intergenic space 1 (IGS1) region, genotyping, and investigation of virulence factors. Antifungal susceptibility was determined using the CLSI broth microdilution method for fluconazole (FLC), itraconazole (ITC), and amphotericin B (AMB). Of these, 24 isolates were identified, including 12 T. asahii, 4 T. inkin, 3 T. faecale, 1 T. coremiiforme, 1 T. japonicum, 2 Cutaneotrichosporon dermatis (formerly T. dermatis), and 1 Apiotrichum mycotoxinivorans (formerly T. mycotoxinivorans). Species-level identification of 2 isolates was not successful; they were described as Trichosporon sp. We observed optimal colonial development at 35-40 °C. Lipase was the major extracellular enzyme produced (100%); caseinase was not produced (0%). Biofilms were produced by all isolates (classified as low). High AMB minimum inhibitory concentration (MIC) was observed, with all strains resistant. Fluconazole was the most active drug among the antifungals tested. However, high MICs for FLC were observed in C. dermatis and A. mycotoxinivorans species, which also showed resistance to ITC and AMB. This study, conducted in the Northern region of Brazil, identified 5 Trichosporon species along with C. dermatis and A. mycotoxinivorans and demonstrated their pathogenic potential through their ability to produce important virulence factors. This may contribute to our understanding of the epidemiology and factors related to the pathogeneses of species in the Trichosporonaceae family.