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Aspergillus spp. cause serious invasive lung infections, and Aspergillus fumigatus is the most commonly encountered clinically significant species. Voriconazole is considered to be the drug of choice for treating A. fumigatus infections; however, rising resistance rates have been reported. We evaluated a matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS)-based method for the differentiation between wild-type and non-wild-type isolates of 20 Aspergillus spp. (including 2 isolates of Aspergillus ustus and 1 of Aspergillus calidoustus that were used as controls due their intrinsic low azole susceptibility with respect to the in vitro response to voriconazole). At 30 and 48 h of incubation, there was complete agreement between Cyp51A sequence analysis, broth microdilution, and MALDI-TOF MS classification of isolates as wild type or non-wild type. In this proof-of-concept study, we demonstrated that MALDI-TOF MS can be used to accurately detect A. fumigatus strains with reduced voriconazole susceptibility. However, rather than proving to be a rapid and simple method for antifungal susceptibility testing, this particular MS-based method showed no benefit over conventional testing methods.

Molecular approaches are now being developed to provide a more rapid and objective identification of fungi compared to traditional phenotypic methods. Ribosomal targets, especially the large-subunit RNA gene (D1-D2 region) and internal transcribed spacers 1 and 2 (ITS1 and ITS2 regions), have shown particular promise for the molecular identification of some fungi. We therefore conducted an assessment of these regions for the identification of 13 medically important Aspergillus species: Aspergillus candidus , Aspergillus ( Eurotium ) chevalieri , Aspergillus ( Fennellia ) flavipes , Aspergillus flavus , Aspergillus fumigatus , Aspergillus granulosus , Aspergillus ( Emericella ) nidulans , Aspergillus niger , Aspergillus restrictus , Aspergillus sydowii , Aspergillus terreus , Aspergillus ustus , and Aspergillus versicolor . The length of ribosomal regions could not be reliably used to differentiate among all Aspergillus species examined. DNA alignment and pairwise nucleotide comparisons demonstrated 91.9 to 99.6% interspecies sequence identities in the D1-D2 region, 57.4 to 98.1% in the ITS1 region, and 75.6 to 98.3% in the ITS2 region. Comparative analysis using GenBank reference data showed that 10 of the 13 species examined exhibited a ≤1-nucleotide divergence in the D1-D2 region from closely related but different species. In contrast, only 5 of the species examined exhibited a ≤1-nucleotide divergence from sibling species in their ITS1 or ITS2 sequences. Although the GenBank database currently lacks ITS sequence entries for some species, and major improvement in the quality and accuracy of GenBank entries is needed, current identification of medically important Aspergillus species using GenBank reference data seems more reliable using ITS query sequences than D1-D2 sequences, especially for the identification of closely related species.

We developed a PCR-based assay to differentiate medically important species of Aspergillus from one another and from other opportunistic molds and yeasts by employing universal, fungus-specific primers and DNA probes in an enzyme immunoassay format (PCR-EIA). Oligonucleotide probes, directed to the internal transcribed spacer 2 region of ribosomal DNA from Aspergillus flavus , Aspergillus fumigatus , Aspergillus nidulans , Aspergillus niger , Aspergillus terreus , Aspergillus ustus , and Aspergillus versicolor , differentiated 41 isolates (3 to 9 each of the respective species; P < 0.001) in a PCR-EIA detection matrix and gave no false-positive reactions with 33 species of Acremonium , Exophiala , Candida , Fusarium , Mucor , Paecilomyces , Penicillium , Rhizopus , Scedosporium , Sporothrix , or other aspergilli tested. A single DNA probe to detect all seven of the most medically important Aspergillus species ( A. flavus , A. fumigatus , A. nidulans , A. niger , A. terreus , A. ustus , and A. versicolor ) was also designed. Identification of Aspergillus species was accomplished within a single day by the PCR-EIA, and as little as 0.5 pg of fungal DNA could be detected by this system. In addition, fungal DNA extracted from tissues of experimentally infected rabbits was successfully amplified and identified using the PCR-EIA system. This method is simple, rapid, and sensitive for the identification of medically important Aspergillus species and for their differentiation from other opportunistic fungi.

A colorimetric assay for antifungal susceptibility testing of Aspergillus species ( Aspergillus fumigatus , Aspergillus flavus , Aspergillus terreus , Aspergillus nidulans , and Aspergillus ustus ) is described based on the reduction of the tetrazolium salt 2,3-bis(2-methoxy-4-nitro-5-[(sulphenylamino)carbonyl]-2H-tetrazolium-hydroxide (XTT) in the presence of menadione as an electron-coupling agent. The combination of 200 μg of XTT/ml with 25 μM menadione resulted in a high production of formazan within 2 h of exposure, allowing the detection of hyphae formed by low inocula of 10 2 CFU/ml after 24 h of incubation. Under these settings, the formazan production correlated linearly with the fungal biomass and less-variable concentration effect curves for amphotericin B and itraconazole were obtained.

A case of invasive pulmonary aspergillosis in an allogeneic bone marrow transplant recipient caused by Aspergillus ustus is presented. A. ustus was also recovered from the hospital environment, which may indicate that the infection was nosocomially acquired. A literature review revealed seven cases of invasive infections caused by A. ustus , and three of these were primarily cutaneous infections. In vitro susceptibility testing of 12 A. ustus isolates showed that amphotericin B and terbinafine had fungicidal activity and that itraconazole and voriconazole had fungistatic activity.

Aspergillus ustus is an uncommon clinical species which is poorly susceptible to antifungals. We report two cases of A. ustus infections that occurred in allogeneic stem cell transplant recipients while they were receiving either voriconazole or caspofungin. Prolonged use of these new antifungal agents may increase the risk of the emergence of resistant organisms.

We report a case of primary cutaneous infection by the emerging fungus Aspergillus ustus in an immunosuppressed patient after a domestic accident. The patient failed to respond to itraconazole and died before receiving a new treatment with amphotericin B. There have been eight other cases reported since 1973, and only two patients survived the infection. In vitro susceptibility testing of seven antifungal drugs showed that terbinafine and the new azole derivative UR-9825 were the most active against this fungus.

Invasive pulmonary aspergillosis (IPA) is a common infection in neutropenic patients and is associated with high mortality. Aspergillus ustus is a species that has only rarely been implicated in human disease. All reported cases of IPA due to A. ustus have been fatal. Here, we describe a case of invasive pulmonary A. ustus infection successfully treated with lung resection and voriconazole. A 43-year-old man with acute myeloid leukemia underwent two courses of chemotherapy and experienced prolonged neutropenia. Treatment with amphotericin B was given for persistent fever. While he was receiving amphotericin B, a progressive opacity developed in the upper right lobe. Lung tissue obtained through pulmonary wedge resection for histology showed a mold with septate hyphae, consistent with IPA due to Aspergillus. A. ustus was grown in culture. The patient was then treated with voriconazole and remained in remission of the mold infection in spite of additional chemotherapy and a leukemic relapse. In summary, this report describes the successful treatment of invasive pulmonary A. ustus infection by lung resection and antifungal treatment with voriconazole in a neutropenic patient.