A novel enzyme immunoassay for the measurement of plasma (1 → 3)-β-D-glucan levels

Identification of Talaromyces marneffei Infection in an HIV-Negative Patient by ITS Sequencing

Disseminated ankle mycosis is a life-threatening systemic infection caused by the emerging opportunistic and lethal fungal pathogen Talaromyces marneffei which is more common in HIV-positive patients. However, an increasing number of infections are occurring in HIV-negative patients. Here, we report a case of Talaromyces marneffei infection in HIV-negative patient. A 50s HIV-negative male patient with fever, cough, bloody sputum expectoration, pulmonary sarcoidosis and body rashes was hospitalized at Zhejiang Provincial People's Hospital. CT scanning showed pulmonary multiple nodules with apical bronchial occlusion, patchy infiltration and pathological biopsy demonstrated bronchiolitis obliterans with organized pneumonia and chronic active inflammation of lung tissue with infiltration of numerous lymphocytes, plasma cells, phagocytes and neutrophils. Laboratory tests revealed significantly increased white blood cells count 18.3 ×109/L, neutrophil count 15.34 ×109/L, monocyte count 0.66 ×109/L, platelet count 517 ×109/L, C-reactive protein 116 mg/L, erythrocyte sedimentation rate 112mm/h. The β-D-glucan test was negative (33.06 pg/mL) while fungal culture of broncho alveolar lavage fluid revealed colonies with temperature-dependent dimorphic growth character and Talaromyces marneffei was confirmed by ITS sequencing of the colonies. The patient exhibited radiological improvement and clinical recuperation after intravenously guttae of voriconazole. Talaromycosis in immunocompetent and HIV-negative individuals is relatively rare and is characterized by an insidious onset, various clinical manifestations, and is clinically challenging. Fungal culture and ITS sequencing are warranted for diagnosis Talaromyces marneffei infection. This is the first report on identification of Talaromyces marneffei infection in an HIV-negative patient with skin involvement by ITS sequencing in Zhejiang.

A Candidemia Case Caused by a Novel Drug-Resistant Candida auris with the Y132F Mutation in Erg11 in Mainland China

Background

Candida auris is a pathogen first found in external ear canal, becoming a major threat to global health. Here, we describe a candidemia case caused by a novel drug-resistant Candida auris strain.

Case Presentation

An 80-year-old patient, with multiple serious medical conditions, was suffered from candidemia caused by Candida auris, died 9 days after admission in our hospital. Phylogenetic analysis indicates that this C. auris isolate (designated BJCA003) belongs to the South Asian clade, carries the Y132F mutation in the protein Erg11. And antibiotic susceptibility test indicated that BJCA003 is resistant to fluconazole and amphotericin B, not susceptible to caspofungin. In addition, this strain has multiple colony and cellular morphologies under different culture conditions.

Conclusion

Strain BJCA003 is a novel drug resistant C. auris strain in mainland China, the Y132F mutation in Erg11 may attribute to fluconazole-resistance, alarming that we still face more challenges about C. auris.

Development of a Highly Sensitive β-Glucan Detection System Using Scanning Single-Molecule Counting Method

To overcome the limitations of the Limulus amebocyte lysate (LAL) assay method for the diagnosis of invasive fungal infection, we applied a reaction system combining recombinant β-glucan binding proteins and a scanning single-molecule counting (SSMC) method. A novel (1→3)-β-D-glucan recognition protein (S-BGRP) and a (1→6)-β-glucanase mutant protein were prepared and tested for the binding of (1→6)-branched (1→3)-β-D-glucan from fungi. S-BGRP and (1→6)-β-glucanase mutant proteins reacted with β-glucan from Candida and Aspergillus spp. Although LAL cross-reacted with plant-derived β-glucans, the new detection system using the SSMC method showed low sensitivity to plant (1→3)-β-D-glucan, which significantly improved the appearance of false positives, a recognized problem with the LAL method. Measurement of β-glucan levels by the SSMC method using recombinant β-glucan-binding proteins may be useful for the diagnosis of fungal infections. This study shows that this detection system could be a new alternative diagnostic method to the LAL method.

Outstanding Contributions of LAL Technology to Pharmaceutical and Medical Science: Review of Methods, Progress, Challenges, and Future Perspectives in Early Detection and Management of Bacterial Infections and Invasive Fungal Diseases

The blue blood of the horseshoe crab is a natural, irreplaceable, and precious resource that is highly valued by the biomedical industry. The Limulus amebocyte lysate (LAL) obtained from horseshoe crab blood cells functions as a surprisingly sophisticated sensing system that allows for the extremely sensitive detection of bacterial and fungal cell-wall components. Notably, LAL tests have markedly contributed to the quality control of pharmaceutical drugs and medical devices as successful alternatives to the rabbit pyrogen test. Furthermore, LAL-based endotoxin and (1→3)-β-D-glucan (β-glucan) assay techniques are expected to have optimal use as effective biomarkers, serving as adjuncts in the diagnosis of bacterial sepsis and fungal infections. The innovative β-glucan assay has substantially contributed to the early diagnosis and management of invasive fungal diseases; however, the clinical significance of the endotoxin assay remains unclear and is challenging to elucidate. Many obstacles need to be overcome to enhance the analytical sensitivity and clinical performance of the LAL assay in detecting circulating levels of endotoxin in human blood. Additionally, there are complex interactions between endotoxin molecules and blood components that are attributable to the unique physicochemical properties of lipopolysaccharide (LPS). In this regard, while exploring the potential of new LPS-sensing technologies, a novel platform for the ultrasensitive detection of blood endotoxin will enable a reappraisal of the LAL assay for the highly sensitive and reliable detection of endotoxemia.

Split Enzyme-Based Biosensors for Structural Characterization of Soluble and Insoluble β-Glucans

β-Glucan is widely distributed in various plants and microorganisms and is composed of β-1,3-linked d-glucose units. It may have a branched short or long side chain of glucose units with β-1,6- or β-1,4-linkage. Numerous studies have investigated different β-glucans and revealed their bioactivities. To understand the structure-function relationship of β-glucan, we constructed a split-luciferase complementation assay for the structural analysis of long-chain β-1,6-branched β-1,3-glucan. The N- and C-terminal fragments of luciferase from deep-sea shrimp were fused to insect-derived β-1,3-glucan recognition protein and fungal endo-β-1,6-glucanase (Neg1)-derived β-1,6-glucan recognition protein, respectively. In this approach, two β-glucan recognition proteins bound to β-glucan molecules come into close proximity, resulting in the assembly of the full-length reporter enzyme and induction of transient luciferase activity, indicative of the structure of β-glucan. To test the applicability of this assay, β-glucan and two β-glucan recognition proteins were mixed, resulting in an increase in the luminescence intensity in a β-1,3-glucan with a long polymer of β-1,6-glucan in a dose-dependent manner. This simple test also allows the monitoring of real-time changes in the side chain structure and serves as a convenient method to distinguish between β-1,3-glucan and long-chain β-1,6-branched β-1,3-glucan in various soluble and insoluble β-glucans.