The etiological structure of mucormycetes isolated from children with oncohematological pathology with description of the clinical case of invasive mucomycosis in patients with impaired immunity

Abstract

Introduction: Mucormycosis is one of the fungal infections caused by fungi (mucormycetes) belonging to the order Mucorales and are mainly part of the genera Apophysomyces, Cuniiinghamella, Lichthemia [formerly Absidia], Mucor, Rhizopus, Rhizomucor, Saksenaea. The causative agents of mucormycosis are widespread in the environment. Fungal infection is manifested by rapidly developing lesions of the skin, mucous membranes, internal organs, and tissues. The most common forms of infection are the rhinoorbital-cerebral and pulmonary forms caused by pathogens of mucormycosis. Gastrointestinal, skin, and disseminated forms of fungal diseases are also registered. The mortality rate in mucormycosis reaches 70% in some cases and depends on the clinical form and the timeliness of the therapy initiated. The diagnosis of mucoromycosis is based on the complex application of various approaches including traditional seeding of biological material, histological analysis of material from affected loci, X-ray, and molecular biological studies. In terms of the treatment of this type of fungal infection, the use of amphotericin B, posaconazole, izavuconazole in combination with surgical rehabilitation of affected tissues has the greatest effectiveness. Purpose: Identification and analysis of the etiological structure of mucormycetes isolated from children with oncohematological pathology and impaired immunity as well as a description of the clinical case of concomitant generalized gastrointestinal mucormycosis against the background of the underlying disease associated with disorder of the immune system. Material and methods: The study includes the results of the isolation of mold fungi (including pathogens of mucoromycosis) from clinically significant biological material for the period from January 2002 to June 2023. To isolate the fungal microflora, traditional microbiological sowing of biomaterial was used followed by generic and specific (in some cases) identification using phenotypic, molecular biological, and mass-spectrometric types of laboratory analysis. When describing the case of invasive mucormycosis, methods of endoscopic and pathomorphological diagnostics were additionally used. Results: The etiological structure of mucoromycetes identified in children with oncohematological pathology and impaired immunity has been studied. As a result, 85 strains of mycelial microflora were isolated from clinically significant biological material obtained from the respiratory organs and respiratory tract (lung biopsies, contents of bronchoalveolar lavage (BAL), and tracheobronchial drainage), which accounted for 30.69% of 277 identified mold micromycetes. At the same time, 12 strains of mucormycetes were identified, which accounted for 14.12% of the total number of fungi found. The isolated mucormycetes were representatives of the genera Mucor, Rhizopus, Rhizomucor, and Lichtheimia [Absidia]. There were also the isolated cases of detection of mucoromycosis pathogens in blood (one strain of Mucor spp. and one strain of Rhizopus spp. out of 222 hemocultures), in urine (one strain of Mucor out of 113 ureacultures), in liver biopsies (one strain of Rhizopus spp.) and gastrointestinal (two strains of Rhizopus microsporus). The clinical case of invasive mucormycosis of the gastrointestinal tract (GI tract), which occurred in a patient with Nijmegen syndrome in the post-transplant period against the background of a coronavirus infection, is described. Conclusion: The total proportion of mucormycosis pathogens (detected in the lungs and in the contents of the respiratory tract) among the total number of filamentous micromycetes reaches 14.12%. The complex application of various diagnostic approaches (including microbiological seeding of biomaterial, X-ray, pathohistochemical and molecular biological studies) makes it possible to reliably verify invasive mucormycosis. In patients with immune defects, despite intensive antifungal therapy, mucormycetes can cause severe forms of invasive fungal infection, up to a fatal outcome.