Saad J. Taj-Aldeen

Fungal Rhinosinusitis: A Categorization and Definitional Schema Addressing Current Controversies

Fungal (rhino‐) sinusitis encompasses a wide spectrum of immune and pathological responses, including invasive, chronic, granulomatous, and allergic disease. However, consensus on terminology, pathogenesis, and optimal management is lacking. The International Society for Human and Animal Mycology convened a working group to attempt consensus on terminology and disease classification.

Prevalent mutator genotype identified in fungal pathogen Candida glabrata promotes multi-drug resistance.

The fungal pathogen Candida glabrata has emerged as a major health threat since it readily acquires resistance to multiple drug classes, including triazoles and/or echinocandins. Thus far, cellular mechanisms promoting the emergence of resistance to multiple drug classes have not been described in this organism. Here we demonstrate that a mutator phenotype caused by a mismatch repair defect is prevalent in C. glabrata clinical isolates. Strains carrying alterations in mismatch repair gene MSH2 exhibit a higher propensity to breakthrough antifungal treatment in vitro and in mouse models of colonization, and are recovered at a high rate (55% of all C. glabrata recovered) from patients. This genetic mechanism promotes the acquisition of resistance to multiple antifungals, at least partially explaining the elevated rates of triazole and multi-drug resistance associated with C. glabrata. We anticipate that identifying MSH2 defects in infecting strains may influence the management of patients on antifungal drug therapy.

Identification of medically relevant species of arthroconidial yeasts by use of matrix-assisted laser desorption ionization-time of flight mass spectrometry.

ABSTRACT Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) was used for an extensive identification study of arthroconidial yeasts, using 85 reference strains from the CBS-KNAW yeast collection and 134 clinical isolates collected from medical centers in Qatar, Greece, and Romania. The test set included 72 strains of ascomycetous yeasts (Galactomyces, Geotrichum, Saprochaete, and Magnusiomyces spp.) and 147 strains of basidiomycetous yeasts (Trichosporon and Guehomyces spp.). With minimal preparation time, MALDI-TOF MS proved to be an excellent diagnostic tool that provided reliable identification of most (98%) of the tested strains to the species level, with good discriminatory power. The majority of strains were correctly identified at the species level with good scores (>2.0) and seven of the tested strains with log score values between 1.7 and 2.0. The MALDI-TOF MS results obtained were consistent with validated internal transcribed spacer (ITS) and/or large subunit (LSU) ribosomal DNA sequencing results. Expanding the mass spectrum database by increasing the number of reference strains for closely related species, including those of nonclinical origin, should enhance the usefulness of MALDI-TOF MS-based diagnostic analysis of these arthroconidial fungi in medical and other laboratories.

Molecular Identification and Susceptibility of Trichosporon Species Isolated from Clinical Specimens in Qatar: Isolation of Trichosporon dohaense Taj-Aldeen, Meis & Boekhout sp. nov.

ABSTRACT Trichosporon species have been reported as emerging pathogens and usually occur in severely immunocompromised patients. In the present work, 27 clinical isolates of Trichosporon species were recovered from 27 patients. The patients were not immunocompromised, except for one with acute myeloid leukemia. Sequence analysis revealed the isolation of Trichosporon dohaense Taj-Aldeen, Meis & Boekhout sp. nov., with CBS 10761T as the holotype strain, belonging to the Ovoides clade. In the D1-D2 large-subunit rRNA gene analysis, T. dohaense is a sister species to T. coremiiforme, and in the internal transcribed spacer analysis, the species is basal to the other species of this clade. Molecular identification of the strains yielded 17 T. asahii, 3 T. inkin, 2 T. japonicum, 2 T. faecale, and 3 T. dohaense isolates. The former four species exhibited low MICs for five antifungal azoles but showed high MICs for amphotericin B. T. dohaense demonstrated the lowest amphotericin B MIC (1 mg/liter). For the majority of T. asahii isolates, amphotericin B MICs were high (MIC at which 90% of isolates were inhibited [MIC90], ≥16 mg/liter), and except for fluconazole (MIC90, 8 mg/liter), the azole MICs were low: MIC90s were 0.5 mg/liter for itraconazole, 0.25 mg/liter for voriconazole, 0.25 mg/liter for posaconazole, and 0.125 mg/liter for isavuconazole. The echinocandins, caspofungin and anidulafungin, demonstrated no activity against Trichosporon species.

Aspergillus osteomyelitis: Epidemiology, clinical manifestations, management, and outcome

BACKGROUND The epidemiology, pathogenesis, diagnosis, and management of Aspergillus osteomyelitis are not well understood. METHODS Protocol-defined cases of Aspergillus osteomyelitis published in the English literature were reviewed for comorbidities, microbiology, mechanisms of infection, clinical manifestations, radiological findings, inflammatory biomarkers, antifungal therapy, and outcome. RESULTS Among 180 evaluable patients, 127 (71%) were males. Possible predisposing medical conditions in 103 (57%) included pharmacological immunosuppression, primary immunodeficiency, and neutropenia. Seventy-three others (41%) had prior open fracture, trauma or surgery. Eighty (44%) followed a hematogenous mechanism, 58 (32%) contiguous infections, and 42 (23%) direct inoculation. Aspergillus osteomyelitis was the first manifestation of aspergillosis in 77%. Pain and tenderness were present in 80%. The most frequently infected sites were vertebrae (46%), cranium (23%), ribs (16%), and long bones (13%). Patients with vertebral Aspergillus osteomyelitis had more previous orthopedic surgery (19% vs 0%; P = 0.02), while those with cranial osteomyelitis had more diabetes mellitus (32% vs 8%; P = 0.002) and prior head/neck surgery (12% vs 0%; P = 0.02). Radiologic findings included osteolysis, soft-tissue extension, and uptake on T2-weighted images. Vertebral body Aspergillus osteomyelitis was complicated by spinal-cord compression in 47% and neurological deficits in 41%. Forty-four patients (24%) received only antifungal therapy, while 121 (67%) were managed with surgery and antifungal therapy. Overall mortality was 25%. Median duration of therapy was 90 days (range, 10-772 days). There were fewer relapses in patients managed with surgery plus antifungal therapy in comparison to those managed with antifungal therapy alone (8% vs 30%; P = 0.006). CONCLUSIONS Aspergillus osteomyelitis is a debilitating infection affecting both immunocompromised and immunocompetent patients. The most common sites are vertebrae, ribs, and cranium. Based upon this comprehensive review, management of Aspergillus osteomyelitis optimally includes antifungal therapy and selective surgery to avoid relapse and to achieve a complete response.

Geographically Structured Populations of Cryptococcus neoformans Variety grubii in Asia Correlate with HIV Status and Show a Clonal Population Structure

Cryptococcosis is an important fungal disease in Asia with an estimated 140,000 new infections annually the majority of which occurs in patients suffering from HIV/AIDS. Cryptococcus neoformans variety grubii (serotype A) is the major causative agent of this disease. In the present study, multilocus sequence typing (MLST) using the ISHAM MLST consensus scheme for the C. neoformans/C. gattii species complex was used to analyse nucleotide polymorphisms among 476 isolates of this pathogen obtained from 8 Asian countries. Population genetic analysis showed that the Asian C. neoformans var. grubii population shows limited genetic diversity and demonstrates a largely clonal mode of reproduction when compared with the global MLST dataset. HIV-status, sequence types and geography were found to be confounded. However, a correlation between sequence types and isolates from HIV-negative patients was observed among the Asian isolates. Observations of high gene flow between the Middle Eastern and the Southeastern Asian populations suggest that immigrant workers in the Middle East were originally infected in Southeastern Asia.

Resistance of Asian Cryptococcus neoformans Serotype A Is Confined to Few Microsatellite Genotypes

Background Cryptococcus neoformans is a pathogenic yeast that causes cryptococcosis, a life threatening disease. The prevalence of cryptococcosis in Asia has been rising after the onset of the AIDS epidemic and estimates indicate more than 120 cases per 1,000 HIV-infected individuals per year. Almost all cryptococcal disease cases in both immunocompromised and immunocompetent patients in Asia are caused by C. neoformans var. grubii. Epidemiological studies on C. neoformans in pan-Asia have not been reported. The present work studies the genetic diversity of the fungus by microsatellite typing and susceptibility analysis of approximately 500 isolates from seven Asian countries. Methodology/Principal Findings Genetic diversity of Asian isolates of C. neoformans was determined using microsatellite analysis with nine microsatellite markers. The analysis revealed eight microsatellite complexes (MCs) which showed different distributions among geographically defined populations. A correlation between MCs and HIV-status was observed. Microsatellite complex 2 was mainly associated with isolates from HIV-negative patients, whereas MC8 was associated with those from HIV-positive patients. Most isolates were susceptible to amphotericin B, itraconazole, voriconazole, posaconazole, and isavuconazole, but 17 (3.4%) and 10 (2%) were found to be resistant to 5-flucytosine and fluconazole, respectively. Importantly, five Indonesian isolates (approximately 12.5% from all Indonesian isolates investigated and 1% from the total studied isolates) were resistant to both antifungals. The majority of 5-flucytosine resistant isolates belonged to MC17. Conclusions The findings showed a different distribution of genotypes of C. neoformans var. grubii isolates from various countries in Asia, as well as a correlation of the microsatellite genotypes with the original source of the strains and resistance to 5-flucytosine.

Importance of Resolving Fungal Nomenclature: the Case of Multiple Pathogenic Species in the Cryptococcus Genus

Cryptococcosis is a major fungal disease caused by members of the Cryptococcus gattii and Cryptococcus neoformans species complexes. After more than 15 years of molecular genetic and phenotypic studies and much debate, a proposal for a taxonomic revision was made. ABSTRACT Cryptococcosis is a major fungal disease caused by members of the Cryptococcus gattii and Cryptococcus neoformans species complexes. After more than 15 years of molecular genetic and phenotypic studies and much debate, a proposal for a taxonomic revision was made. The two varieties within C. neoformans were raised to species level, and the same was done for five genotypes within C. gattii. In a recent perspective (K. J. Kwon-Chung et al., mSphere 2:e00357-16, 2017, https://doi.org/10.1128/mSphere.00357-16 ), it was argued that this taxonomic proposal was premature and without consensus in the community. Although the authors of the perspective recognized the existence of genetic diversity, they preferred the use of the informal nomenclature “C. neoformans species complex” and “C. gattii species complex.” Here we highlight the advantage of recognizing these seven species, as ignoring these species will impede deciphering further biologically and clinically relevant differences between them, which may in turn delay future clinical advances.

Uncommon opportunistic yeast bloodstream infections from Qatar

Eleven uncommon yeast species that are associated with high mortality rates irrespective of antifungal therapy were isolated from 17/187 (201 episodes) pediatric and elderly patients with fungemia from Qatar. The samples were taken over a 6-year period (January 2004-December 2010). Isolated species included Kluyveromyces marxianus, Lodderomyces elongisporus, Lindnera fabianii, Candida dubliniensis, Meyerozyma guilliermondii, Candida intermedia, Pichia kudriavzevii, Yarrowia lipolytica, Clavispora lusitaniae, Candida pararugosa, and Wickerhamomyces anomalus. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry provided correct identifications compared with molecular analysis testing of the same isolates. Low minimal inhibitory concentrations were found when isavuconazole and voriconazole were used for all uncommon yeast species evaluated in this study. Resistance to antifungal drugs was low and remained restricted to a few species.

Gangrenous necrosis of the diabetic foot caused by Fusarium acutatum

Foot infections are common and serious complications of diabetic patients. We report the case of a 68-year-old patient with a diabetic foot infection that developed into a gangrenous necrosis. Fusarium spp. was isolated on two successive occasions with no other associated microorganisms. Histopathology demonstrated invasion of the fungus into the tisssue. These findings suggested an infection rather than colonization. A detailed morphological study showed that the isolate was Fusarium acutatum, which was confirmed by rDNA sequencing. This fungus is found only in Asia and has not been previously reported as a human pathogen.