Experimental Phaeohyphomycosis of Curvularia lunata

Identification and characterization of multiple fungal pathogens associated with brown spot disease of rice in India

Brown spot (BS) disease causes significant losses to rice productivity. In this study, a roving survey in the Karnataka state of India revealed a wider distribution of BS with a percent disease index range of 20.56-50.74. From the symptomatic geo-distinct samples, pure cultures of 63 isolates were obtained. Based on the conidial morphology, 63 isolates were identified as Bipolaris oryzae (Bo) (n = 40), Curvularia lunata (Cl) (n = 15), and Exserohilum rostratum (Er) (n = 08). The taxonomic identity was further confirmed via ITS-sequencing. A pathogenicity assay on a BS-susceptible rice cultivar GNV-05-01 confirmed the pathogenicity of all three pathogens, which induces typical BS disease on test plants. Further, on PDA media, all isolates of three pathogens showed significant cultural diversity for mycelial color, colony type, and sporulation. We further studied the in-planta distribution of three pathogens on a randomly collected 600 BS spots from 10 different rice fields, which indicated that 77.83%, 17.33%, and 4.83% of the typical BS were produced by Bo, Cl, and Er, respectively. The ITS region was sequenced for selected 9, 7, and 3 isolates of Bo, Cl, and Er, respectively, and analyzed for their nucleotide and haplotype diversity, and phylogenetic relationships. A phylogenetic study identified the unique clustering patterns, and haplotyping indicated 3, 4, and 6 haplotypes. Tajima's D (D) test showed several rare alleles in the ITS regions. This is the first comprehensive study reporting the three fungal pathogens causing BS of rice and it is useful for re-designing the screening protocol for the host plant resistance breeding program.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04033-3.

Production and characterization of melanin pigment from black fungus Curvularia soli AS21 ON076460 assisted gamma rays for promising medical uses

Owing to the growing need for natural materials in different fields, studying melanin production from biological sources is imperative. In the current study, the extracellular melanin pigment was produced by the fungus Curvularia soli AS21 ON076460. The factors that affect the production of melanin were optimized by the Plackett-Burman design (P-BD). The effect of gamma irradiation on melanin productivity was investigated. The maximum melanin yield (3.376 mg/L) was elicited by a stimulus of gamma irradiation at 1.0 kGy. The results evoked that, Curvularia soli AS21 ON076460 melanin exhibited excellent antimicrobial activity against all tested bacteria and fungi. Klebsiella pneumoniae ATCC 13883 and P. digitatum were mostly affected by melanin registering the inhibition zone diameters of 37.51 ± 0.012 and 44.25 ± 0.214 mm, respectively. Moreover, Curvularia soli AS21 ON076460 melanin indicated a significant antiviral efficacy (77% inhibition) of Herpes simplex virus (HSV1). The melanin pigment showed antioxidant activities with IC50 of 42 ± 0.021 and 17 ± 0.02 µg/mL against DPPH and NO, respectively. Melanin had cytotoxic action against human breast cancer and skin cancer cell lines (Mcf7and A431) as well as exerting a low percentage of cell death against normal skin cell lines (Hfb4). Melanin was effective in wound management of human skin cells by 63.04 ± 1.83% compared with control (68.67 ± 1.10%). The novelty in the study is attributed to the possibility of using gamma rays as a safe method in small economic doses to stimulate melanin production from the fungi that have been isolated. In summary, melanin produced from fungi has significant biological activities that encourage its usage as a supportive medical route.

Trans-kingdom fungal pathogens infecting both plants and humans, and the problem of azole fungicide resistance

Azole antifungals are abundantly used in the environment and play an important role in managing fungal diseases in clinics. Due to the widespread use, azole resistance is an emerging global problem for all applications in several fungal species, including trans-kingdom pathogens, capable of infecting plants and humans. Azoles used in agriculture and clinics share the mode of action and facilitating cross-resistance development. The extensive use of azoles in the environment, e.g., for plant protection and wood preservation, contributes to the spread of resistant populations and challenges using these antifungals in medical treatments. The target of azoles is the cytochrome p450 lanosterol 14-α demethylase encoded by the CYP51 (called also as ERG11 in the case of yeasts) gene. Resistance mechanisms involve mainly the mutations in the coding region in the CYP51 gene, resulting in the inadequate binding of azoles to the encoded Cyp51 protein, or mutations in the promoter region causing overexpression of the protein. The World Health Organization (WHO) has issued the first fungal priority pathogens list (FPPL) to raise awareness of the risk of fungal infections and the increasingly rapid spread of antifungal resistance. Here, we review the main issues about the azole antifungal resistance of trans-kingdom pathogenic fungi with the ability to cause serious human infections and included in the WHO FPPL. Methods for the identification of these species and detection of resistance are summarized, highlighting the importance of these issues to apply the proper treatment.

Severe influenza A virus pneumonia complicated with Curvularia lunata infection: Case Report

Human infection with Curvularia lunata (C. lunata) is exceptionally rare. A 23-year-old female patient contracted both bacterial and Curvularia lunata infections during influenza A virus infection. Multiple etiological tests were performed repeatedly during hospitalization due to fluctuations in condition. On the 17th day after hospital admission, mold hyphae were discovered in the pathogen culture of the patient’s bronchoalveolar lavage fluid during one of these examinations. The patient was suspected to have a filamentous fungal infection. Consequently, we further obtained sputum samples for fungal culture, which confirmed the diagnosis of Curvularia infection. The patient, in this case, was in a critical condition, experiencing complications of lung abscess, pneumothorax, sepsis, and multiorgan failure. Despite prompt initiation of antifungal therapy including amphotericin B cholesteryl sulfate complex and isavuconazole upon detection of the fungal infection and concurrent administration of active organ function support treatment, the patient’s condition rapidly deteriorated due to compromised immune function. Ultimately, on the 27th day of treatment, the patient succumbed to septic shock and multiple organ dysfunction syndrome. This is the first case of Curvularia lunata infection in our hospital. In this paper, we aim to raise awareness of Curvularia lunata infection and to emphasize that the possibility of this fungal infection should be considered in patients with severe pneumonia caused by influenza A virus and that empirical antifungal therapy should be given promptly when the patient has invasive lung damage.

Severe influenza A virus pneumonia complicated with Curvularia lunata infection: Case Report

Human infection with Curvularia lunata (C. lunata) is exceptionally rare. A 23-year-old female patient contracted both bacterial and Curvularia lunata infections during influenza A virus infection. Multiple etiological tests were performed repeatedly during hospitalization due to fluctuations in condition. On the 17th day after hospital admission, mold hyphae were discovered in the pathogen culture of the patient's bronchoalveolar lavage fluid during one of these examinations. The patient was suspected to have a filamentous fungal infection. Consequently, we further obtained sputum samples for fungal culture, which confirmed the diagnosis of Curvularia infection. The patient, in this case, was in a critical condition, experiencing complications of lung abscess, pneumothorax, sepsis, and multiorgan failure. Despite prompt initiation of antifungal therapy including amphotericin B cholesteryl sulfate complex and isavuconazole upon detection of the fungal infection and concurrent administration of active organ function support treatment, the patient's condition rapidly deteriorated due to compromised immune function. Ultimately, on the 27th day of treatment, the patient succumbed to septic shock and multiple organ dysfunction syndrome. This is the first case of Curvularia lunata infection in our hospital. In this paper, we aim to raise awareness of Curvularia lunata infection and to emphasize that the possibility of this fungal infection should be considered in patients with severe pneumonia caused by influenza A virus and that empirical antifungal therapy should be given promptly when the patient has invasive lung damage.