[Prevalence of fungal infections detected from biopsies and autopsies in the past 11 years at the University Hospital Joan XXIII in Tarragona, Spain]

Triintsin, a human pathogenic fungus-derived defensin with broad-spectrum antimicrobial activity

Since there is a symbiotic and competitive relationship between microorganisms in the same ecological niche, fungal defensins have been found to be important resources for antimicrobial peptides. Here, a fungal defensin, triintsin, was characterized in a clinical isolate of Trichophyton interdigitale from a patient with onychomycosis. The comparison of its genomic and mRNA sequences showed the gene organization and structure of three coding exons separated by two introns. The precursor peptide of triintsin contained 85 amino acid residues, which were composed of three parts including an N-terminal signal domain of 21 residues, a pro-peptide of 47 residues that ended at lysine-arginine and a mature peptide of 38 residues at the C-terminus. The 3D-structure established by homology modeling revealed that triintsin presented a representative typical cysteine-stabilized α-helical and β-sheet fold. The reductive linear peptide of triintsin was obtained by chemical synthesis. After cyclization to form three pairs of disulfide bonds, the oxidative-type peptide displayed broad-spectrum antimicrobial activity against both gram-positive and gram-negative bacteria but also showed anti-fungal activity. Moreover, triintsin can effectively inhibit the growth of clinical strains. Altogether, the peptide is a human pathogenic fungus-derived defensin with broad-spectrum antimicrobial activity.

Current challenges in the microbiological diagnosis of invasive aspergillosis

The diagnosis of invasive aspergillosis is challenging because no sufficiently sensitive or specific tests have been developed to date. Infection can only be confirmed using histology, although this approach is unavailable in many patients. Therefore, diagnosis of invasive aspergillosis is based on a combination of the presence of host factors, radiological and clinical findings, and mycological criteria. In clinical practice, lack of optimal diagnostics often leads to empirical therapy and great cost and toxicity. Mycological criteria include the isolation of Aspergillus from clinical samples or the detection of biomarkers in fluids. Culture is cheap and easy and enables the identification of fungi and performance of antifungal susceptibility testing; however, it has low sensitivity and specificity. Non-culture-based diagnosis is based on the detection of fungal biomarkers such as galactomannan or (1 → 3)-β-D-glucan in normally sterile body fluids. These procedures enable faster and more sensitive and specific detection of Aspergillus; however, diagnostic accuracy is affected by the patient's underlying condition. Finally, while detection of Aspergillus DNA is promising, the lack of standardization limits its inclusion as a mycological criterion for the definition of probable invasive aspergillosis. New diagnostic procedures based on lateral flow technology are also promising but need further evaluation. In the present review, we discuss current culture-based and non-culture-based procedures for the microbiological diagnosis of invasive aspergillosis.