High-resolution melting analysis assay for identification of Fonsecaea species

Role of Dectin-1 in immune response of macrophages induced by Fonsecaea monophora wild strain and melanin-deficient mutant strain

Chromoblastomycosis is a chronic granulomatous subcutaneous fungal disease caused mainly by Fonsecaea monophora in southern China. Melanin is an important virulence factor in wild strain (Mel+), and the strains lack of the polyketide synthase gene is a melanin-deficient mutant strain (Mel-). We investigated the effect of melanin in F. monophora on Dectin-1 receptor-mediated immune responses in macrophages. Conidia and tiny hyphae of Mel+ and Mel- were co-cultured with THP-1 macrophages expressing normal or low levels of Dectin-1. Compare the killing rate, phagocytosis rate, and expression levels of the inflammatory cytokines tumour necrosis factor-α, interleukin-1β, interleukin-6, and nitric oxide in each group. The results showed that the killing rate, phagocytosis rate, and pro-inflammatory factor levels of Mel+ infected macrophages with normal expression of Dectin-1 were lower than those of Mel-. And the knockdown of Dectin-1 inhibited the phagocytic rate, killing rate, and proinflammatory factor expression in macrophages infected with Mel+ and Mel-. And there was no significant difference in the above indexes between Mel+ and Mel- groups in Dectin-1 knockdown macrophages. In summary, the study reveals that melanin of F. monophora inhibits the immune response effect of the host by hindering its binding to Dectin-1 on the surface of macrophage, which may lead to persistent fungal infections.

[Long-pulsed 1064 nm Nd: YAG laser combined with terbinafine against chromoblastomycosis caused by Fonsecaea nubica and the effect of laser therapy in a Wistar rat model]

We report a case of chromoblastomycosis caused by Fonsecaea nubica, which was successfully treated by long-pulsed 1064 nm Nd: YAG laser combined with terbinafine. A 60-year-old man was admitted for the presence of a 30 mm×40 mm erythematous plaque on the dorsum of his right hand for about 10 months without any subjective symptoms. Both microscopic examination and tissue biopsy of the lesion showed characteristic sclerotic bodies of chromoblastomycosis. Lesion tissue culture on SDA at 26 ℃ for 2 weeks resulted in a black colony, and slide culture identified the isolate as Fonsecaea species. ITS sequence analysis of the isolate showed a 99% homology with F. nubica strain KX078407. The in vitro susceptibility of the isolate to 9 antifungal agents was determined using the microdilution method according to the guidelines of CLSI M38-A2 protocol, and terbinafine showed the lowest MIC (0.125 μg/ml). We subsequently established a Wistar rat model of chromoblastomycosis using the clinical isolate F. nubica and treated the rats with long-pulsed 1064 nm Nd: YAG laser (pulse width of 3.0 ms, fluence of 24 J/cm², spot size of 3 mm, frequency of 4 Hz, repeated 3 times at an interval of 30 s) twice a week for a total of 8 sessions. Although the laser treatment alone was not able to eliminate the fungi, histopathological examination showed the aggregation of numerous lymphocytes in the local affected tissue, indicating an immune response that consequently facilitate the regression of the lesion. The patient was successfully treated by long-pulsed 1064 nm Nd: YAG laser once a week combined with terbinafine (0.25 /bid) for 8 weeks, and follow-up for 20 months did not reveal any signs of recurrence.

Transcriptional profiling of macrophages infected with Fonsecaea monophora

Fonsecaea monophora is a member of dematiaceous fungi capable of causing chromoblastomycosis through traumatic injury. However, little is known about the pathogenesis and early interactions between F. monophora and host. The aim of this study was to explore the potential mechanism of macrophages against F. monophora, especially the role of melanin during the pathogenic process. We carried out RNA sequencing based on the Illumina system. It showed that according to melanin contents, different strains of F. monophora induced different transcriptional profilings in macrophages. Functional analyses suggested the biological functions of differentially expressed genes were closely related to immune response, and the melanin might affect the interactions by regulating the MAPK signalling pathway of macrophages. Our results provide insights into the pathogenesis of infection by F. monophora conidia.

Chromoblastomycosis Caused by Fonsecaea nubica: First Report in Northern China and Literature Review

Chromoblastomycosis is found worldwide with higher incidence in tropical and subtropical regions. Fonsecaea spp. is one of the major causative agents of this disease. First case of chromoblastomycosis due to Fonsecaea nubica in Northern China is reported in a 75-year-old Chinese male. We firstly summarized molecular identification methods of Fonsecaea spp. and all the strains of F. nubica reported in the literature. Sequencing of internal transcribed spacer alone and/or combined with actin (ACT1), partial cell division cycle (CDC42) and partial beta-tubulin (BT2) were most commonly used to identify species, while lactase (Lac), homogentisate (HmgA) and polyketide synthase (PKS1) were also used in some cases. Most strains were isolated from South America and Eastern China. Five clinical cases of chromoblastomycosis due to F. nubica from Asia and Europe were also reviewed. All the five patients were male, over 30 years old, and their lesions occurred after trauma.

Chromoblastomycosis: clinical experience and review of literature

BACKGROUND

Chromoblastomycosis is a tropical chronic infectious dermatosis characterized by the moriform bodies. To review all cases of chromoblastomycosis attended in the reference service of dermatology.

METHODS

Series of cases of chromoblastomycosis attended in a dermatology reference service. Through an integrated system search of assistance, based on CID-10 B43, we reviewed epidemiological and comorbidities data, clinical presentations, treatments, and outcomes of each clinical case.

RESULTS

From 2011 to 2017, we had five new cases of chromoblastomycosis. The average age was 65.6 years. All of them were men. One patient was HIV-positive, and another patient was immunosuppressed by the use of mycophenolate mofetil and prednisone due to renal transplant. Two patients had no history of evident trauma. The time between onset of symptoms and diagnosis ranged from 7 to 600 months. Fonsecaea pedrosoi was the isolated fungi. All cases were formally confirmed. Itraconazole with or without other therapies was effective in all cases.

CONCLUSIONS

We report five never reported cases of chromoblastomycosis, and we review the clinical experience in diagnosis and treatment of chromoblastomycosis, an infrequent and neglected subcutaneous mycosis.

High-resolution melting analysis assay for identification of Fonsecaea species

BACKGROUND

Chromoblastomycosis (CBM) is a chronic fungal disease. In China, the principle etiologic agent was a group of dematiaceous fungi, including Fonsecaea monophora, Fonsecaea nubica, and Cladophialophora carrionii. Although the Fonsecaea species have similar morphology, their pathogenicity is quite different. This study aims to establish a new solution for early identification of Fonsecaea species because of their distinctive potential infection risk.

METHODS

Five reference strains and 35 clinical isolates from patients with CBM, preserved in our laboratory, were used in this study. The universal primer ITS1 and ITS2 were chosen to amplify the highly conserved regions of rDNA. High-resolution melting (HRM) analysis was performed using the LIGHTCYCLER^® 96 System. All the amplicons were verified by direct sequencing and the sequence were aligned with those in GenBank by BLAST analysis.

RESULTS

We successfully differentiated the five strains according to their different Tm values and curve shapes. The 35 clinical isolates from patients were identified as 24 strains for F. monophora and 11 strains for F. nubica, which is consistent with the DNA sequencing results.

CONCLUSION

It is the first time to use HRM analysis for identification of Fonsecaea species. Since the CBM etiologic agent in South China is mainly F. monophora and F. nubica, this strategy is sufficient to be applied in the clinical examination with high accuracy, speed, and throughput.