Molecular Identification of Rhizomucor pusillus as a Cause of Sinus-Orbital Zygomycosis in a Patient with Acute Myelogenous Leukemia

Abstract

Sinus-orbital zygomycosis caused by Rhizomucor pusillus in a patient with acute myelogenous leukemia is described. Identification was achieved by sequencing of the internal transcribed spacer (ITS) regions of the rRNA gene and by expression of zygospores in mating. This report highlights the value of ITS sequencing as a diagnostic tool for the identification of R. pusillus and expands the understanding of infection types caused by this zygomycete. CASE REPORTA 62-year-old male Native American rancher from Nebraska was diagnosed with acute myelogenous leukemia. He was treated with standard induction and consolidation chemotherapy followed by a low-intensity related allogeneic peripheral stem cell transplant. The patient received fluconazole prophylaxis and was placed on granulocyte-macrophage colony-stimulating factor (GM-CSF) on the day of transplant. On day 8 posttransplant (PT) the patient had an absolute neutrophil count of 300 cells per mm 3 and complained of nasal congestion. A nasal washing was positive for parainfluenza virus, but cultures for bacteria and fungi were negative. A computed tomography scan of the sinuses showed pansinusitis. On day 9 PT, the absolute neutrophil count was 1,380 cells per mm 3 , at which time GM-CSF was discontinued. Over the next 4 days, the sinusitis symptoms continued with the development of right-sided periorbital edema. On day 13 PT a magnetic resonance image confirmed pansinusitis with diffuse mucosal thickening and bilateral proptosis. Broad-spectrum antibiotics were initiated. The patient was subsequently taken to the operating room for a bilateral total ethmoidectomy and sphenoidectomy; culture and histopathological exam of tissue were negative for pathogens. Amphotericin B (AMB) lipid complex (Abelcet; Enzon Pharmaceuticals, Bridgewater, NJ) was started at 5 mg per kg for presumed fungal sinusitis. Over the next 3 days, the patient had fever spikes to 39.5°C, and on day 16 PT he developed complete loss of vision in the right eye with orbital fixation. On day 18 PT, the patient underwent a bilateral total ethmoidectomy, bilateral maxillary and sphenoid debridement, and a right orbitotomy. The pathological exam of the sphenoid and ethmoid tissues reported "fibrovascular changes and acute inflammation with necrosis containing broad and irregularly shaped non-septate hyphae." Based on diagnosis of an invasive mold infection, the AMB lipid complex was increased to 7.5 mg per kg, AMB nasal irrigation was also initiated, and GM-CSF was restarted. Fungal cultures from the sinus biopsy material plated onto Sabouraud dextrose agar (Remel, Lenexa, Kansas) incubated at 30°C grew a mold within 4 days that was morphologically identified as a Mucor species. Sinus tissue extract and a subculture of the isolate were subsequently submitted to the Molecular Mycology Laboratory at the University of Nebraska Medical Center (UNMC) for further evaluation. DNA extracted from both the sinus tissue and the culture isolate was tested using a molecular assay targeting the internal transcribed s...

Identification of fungal pathogens in a patient with acute myelogenic leukemia using a pathogen detection array technology

“…4 Thus, molecular assays were developed to identify specific species of zygomycetes. These include sequencing of internal transcribed spacer (ITS) region, [5][6][7][8] 28S rRNA 9 and non-sequencing based tests like polymerase chain reaction (PCR) with restriction fragment length polymorphism (RFLP), 10,11 real-time PCR using melting curve analysis, 12 multiplex PCR using specific DNA probes in a microarray based assay, 13 and PCR assay using the Luminex xMAP hybridization method.…”

Isolation and identification of Rhizomucor pusillus from rhinofacial mucormycosis in a diabetic patient

“…The underlying diseases in these cases were acute leukaemia (n57) and non-Hodgkin's lymphoma with renal transplantation and aplastic anaemia (n51). The rhino-facial and rhino-orbito-facial R. pusillus infections were reported for an 11-year-old boy with acute leukaemia and a 38-year-old woman with diabetic ketoacidosis, respectively (Iwen et al, 2005). R. pusillus infection may also initially appear as a sino-orbital infection that rapidly invades the brain in patients with haematological malignancies.…”

Meningoencephalitis caused by a zygomycete fungus (Basidiobolus) associated with septic shock in an immunocompetent patient: 1-year follow-up after treatment

“…In approximately 30 to 40% of cases, nonseptate hyphae are detected in the samples used for tissue biopsy, but culture is negative. Nevertheless, one approach to searching for this type of fungus is its molecular identification (12,13,(17)(18)(19). Recently, Alvarez et al (20) identified 190 strains of zygomycetes that had been previously classified on the basis of morphology.…”