Eumycetoma of the Foot due to Fusarium solani in a Person with Diabetes Mellitus: Report of a Case and Review of Literature

An updated list of eumycetoma causative agents and their differences in grain formation and treatment response

SUMMARYIn 2023, the World Health Organization designated eumycetoma causative agents as high-priority pathogens on its list of fungal priority pathogens. Despite this recognition, a comprehensive understanding of these causative agents is lacking, and potential variations in clinical manifestations or therapeutic responses remain unclear. In this review, 12,379 eumycetoma cases were reviewed. In total, 69 different fungal species were identified as causative agents. However, some were only identified once, and there was no supporting evidence that they were indeed present in the grain. Madurella mycetomatis was by far the most commonly reported fungal causative agent. In most studies, identification of the fungus at the species level was based on culture or histology, which was prone to misidentifications. The newly used molecular identification tools identified new causative agents. Clinically, no differences were reported in the appearance of the lesion, but variations in mycetoma grain formation and antifungal susceptibility were observed. Although attempts were made to explore the differences in clinical outcomes based on antifungal susceptibility, the lack of large clinical trials and the inclusion of surgery as standard treatment posed challenges in drawing definitive conclusions. Limited case series suggested that eumycetoma cases caused by Fusarium species were less responsive to treatment than those caused by Madurella mycetomatis. However, further research is imperative for a comprehensive understanding.

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.

Invasive fusariosis

Invasive fusariosis is a serious invasive fungal disease, affecting immunocompetent and, more frequently, immunocompromised patients. Localized disease is the typical clinical form in immunocompetent patients. Immunocompromised hosts at elevated risk of developing invasive fusariosis are patients with acute leukemia receiving chemotherapeutic regimens for remission induction, and those undergoing allogeneic hematopoietic cell transplant. In this setting, the infection is usually disseminated with positive blood cultures, multiple painful metastatic skin lesions, and lung involvement. Currently available antifungal agents have poor in vitro activity against Fusarium species, but a clear-cut correlation between in vitro activity and clinical effectiveness does not exist. The outcome of invasive fusariosis is largely dependent on the resolution of immunosuppression, especially neutrophil recovery in neutropenic patients.

The First Case of Fusarium falciforme Eumycetoma in Sudan and an Extensive Literature Review about Treatment Worldwide

Eumycetoma is an infectious disease caused by various fungal pathogens. The disease is characterised by black and pale-yellowish grain discharge. In this communication, we report a case of eumycetoma with a pale grain foot-eumycetoma caused by Fusarium falciforme. The patient presented at the outpatient clinic of the Mycetoma Research Centre in Sudan. The causative agent was initially misidentified as Aspergillus nidulans based on its seemingly similar histopathological appearance. However, sequencing the internally transcribed spacer region of the extracted grain confirmed infection with Fusarium falciforme. Although the patient received Itraconazole and underwent surgical excision, the disease was recurrent. To our knowledge, this is the first report on Fusarium falciforme causing eumycetoma in Sudan, indicating the expansion of the geographical distribution of this pathogen. This calls for raising the awareness of healthcare providers and improving the diagnostic and surveillance systems in at-risk areas to improve the case management and reduce the threat of further spread. Considering the potential impacts of F. falciforme infection including threatening the global health, food security, and ecosystem balance, as well as loss of biodiversity and negative socioeconomic changes in endemic countries, we recommend the implementation of an integrated transdisciplinary One Health strategy for the prevention and control of emerging infectious diseases including F. falciforme.

Comparison of molecular and MALDI-TOF MS identification and antifungal susceptibility of clinical Fusarium isolates in Southern China

BACKGROUND

Fusarium species are opportunistic causative agents of superficial and disseminated human infections. Fast and accurate identification and targeted antifungal therapy give help to improve the patients' prognosis.

OBJECTIVES

This study aimed to evaluate the effectiveness of matrix-assisted laser desorption ionisation time of flight mass spectrometry (MALDI-TOF MS) for Fusarium identification, and investigate the epidemiology and antifungal susceptibility profiles of clinical Fusarium isolates in Southern China.

METHODS

There were 95 clinical Fusarium isolates identified by DNA sequencing of translation elongation factor 1-alpha (TEF1α) and MALDI-TOF MS, respectively. Antifungal susceptibility testing of isolates was performed by broth microdilution according to the CLSI approved standard M38-A3 document.

RESULTS

Seven species complexes (SC) with 17 Fusarium species were identified. The most prevalent SC was the F. solani SC (70.5%, 67/95), followed by the F. fujikuroi SC (16.8%, 16/95). F. keratoplasticum within the F. solani SC was the most prevalent species (32.6%, 31/95). There were 91.6% (87/95) of isolates identified by MALDI-TOF MS at the SC level. In most of species, amphotericin B and voriconazole showed lower MICs compared to itraconazole and terbinafine. The F. solani SC showed higher MICs to these antifungal agents compared to the other SCs. There were 10.5% (10/95) of strains with high MICs for amphotericin B (≥8 μg/ml), terbinafine (≥32 μg/ml) and itraconazole (≥32 μg/ml) simultaneously, mostly focusing on F. keratoplasticum (9/10).

CONCLUSION

MALDI-TOF MS exhibited good performance on the identification of Fusarium strains at the SC level. The F. solani SC was the most prevalent clinical SC in Southern China. The MICs varied significantly among different species or SCs to different antifungal agents.

Mycetoma: Development of Diagnosis and Treatment

Mycetoma describes a heterogeneous group of cutaneous and subcutaneous infections caused by either fungi (eumycetomas) or bacteria (actinomycetomas). It is characterized by a triad of clinical symptoms: painless subcutaneous tumor-like swelling, multiple sinuses and fistulas, and discharged grains in pus. This predominantly affects the feet in more than 70% of patients. It is endemic in the “mycetoma belt” regions, including Africa, South America, and South Asia. Autochthonous mycetoma is rare in the United States of America (USA). We recently reported a Latin American immigrant with eumycetoma in the State of Maryland, USA. With millions of immigrants from endemic regions, the true number of mycetomas in the USA is most likely higher than currently recognized. With the aim to raise the awareness of clinicians about mycetoma, especially dermatologists and podiatrists, we update the development of the epidemiology, etiology, clinical presentations, pathogenesis, diagnosis, differential diagnosis, and treatment of mycetoma.

Mycetoma due to Aspergillus flavus in a diabetic patient: Case report and literature review

Diabetes mellitus patients are prone to cutaneous and subcutaneous fungal infections due to pathogenic fungi, including dermatophytes, Mucorales, Candida, Aspergillus, and Fusarium species. Here, we report a case of A. flavus mycetoma confirmed by isolation and molecular identification. The case was a 38-year-old male farmer with a seven-year history of type 2 diabetes mellitus, living in Khuzestan, southwest of Iran. The patient presented with a right foot swelling associated with a nodule and multiple discharging sinuses following trauma sustained on the foot while working barefoot on the rice farm, a year ago. The nodule appeared at the site of the trauma two months after the injury. The initial diagnosis was based on direct microscopic examination of lesions scraping using 20% potassium hydroxide and radiology. Molecular analysis confirmed the isolates to be A. flavus. In vitro susceptibility of the isolate to voriconazole, posaconazole, caspofungin, itraconazole, and amphotericin B was determined. Treatment with voriconazole (200 mg twice daily) stopped the purulent discharge, reduced the swelling, and improved the clinical condition within two months. The study emphasizes the importance of wearing footwear to prevent skin trauma as the main risk factor of patient involvement.