Mohammad T Hedayati1,2, Mojtaba Taghizadeh-Armaki3, Hossein Zarrinfar4, Akbar Hoseinnejad2, Saham Ansari5, Mahdi Abastabar1,2, Halil Er6, Betil Özhak6, Dilara Öğünç6, Macit Ilkit7, Seyedmojtaba Seyedmousavi1,8,9. 1. Invasive Fungi Research Center, Mazandaran University of Medical Sciences, Sari, Iran. 2. Department of Medical Mycology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran. 3. Department of Medical Parasitology and Mycology, School of Medicine, Babol University of Medical Sciences, Babol, Iran. 4. Allergy Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. 5. Department of Medical Parasitology and Mycology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran. 6. Department of Microbiology, Faculty of Medicine, University of Akdeniz, Antalya, Turkey. 7. Division of Mycology, Department of Microbiology, Faculty of Medicine, University of Çukurova, Adana, Turkey. 8. Center of Expertise in Microbiology, Infection Biology and Antimicrobial Pharmacology, Tehran, Iran. 9. Microbiology Service, Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, USA.
Abstract
BACKGROUND: Aspergillus flavus is a major cause of severe non-invasive fungal infections in the Middle Eastern countries. However, it is difficult to distinguish A flavus from A oryzae. OBJECTIVES: To assess the potential of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in discriminating between A flavus and A oryzae and compare it with β-tubulin gene sequencing. METHODS: We used the Bruker Daltonik MALDI-TOF MS system to analyse 200 clinical and environmental A flavus isolates and one A pseudonomius and one A alliaceus (Aspergillus section Flavi) isolate a priori identified as such by sequencing of the β-tubulin gene. RESULTS: All 200 A flavus isolates were identified at the genus level and 176 (88%) at the species levels by MALDI-TOF MS based on the spectral log-scores (≥2.0 and 1.7-1.99, respectively); among them, only 18 (10.2%) were confirmed as A flavus, whereas 35 (19.9%) were identified as A oryzae and 123 (69.9%) as A flavus/A oryzae. Aspergillus pseudonomius and A alliaceus were misidentified as A flavus and A parasiticus with log-score values of 1.39 and 1.09, respectively. CONCLUSIONS: The results indicate that the commercially available Bruker Daltonik MALDI-TOF MS score database cannot separate A flavus and A oryzae species. We also showed that establishment of an in-house library is a useful tool to discriminate closely related Aspergillus species, including A flavus and A oryzae.
BACKGROUND:Aspergillus flavus is a major cause of severe non-invasive fungal infections in the Middle Eastern countries. However, it is difficult to distinguish A flavus from A oryzae. OBJECTIVES: To assess the potential of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) in discriminating between A flavus and A oryzae and compare it with β-tubulin gene sequencing. METHODS: We used the Bruker Daltonik MALDI-TOF MS system to analyse 200 clinical and environmental A flavus isolates and one A pseudonomius and one A alliaceus (Aspergillus section Flavi) isolate a priori identified as such by sequencing of the β-tubulin gene. RESULTS: All 200 A flavus isolates were identified at the genus level and 176 (88%) at the species levels by MALDI-TOF MS based on the spectral log-scores (≥2.0 and 1.7-1.99, respectively); among them, only 18 (10.2%) were confirmed as A flavus, whereas 35 (19.9%) were identified as A oryzae and 123 (69.9%) as A flavus/A oryzae. Aspergillus pseudonomius and A alliaceus were misidentified as A flavus and A parasiticus with log-score values of 1.39 and 1.09, respectively. CONCLUSIONS: The results indicate that the commercially available Bruker Daltonik MALDI-TOF MS score database cannot separate A flavus and A oryzae species. We also showed that establishment of an in-house library is a useful tool to discriminate closely related Aspergillus species, including A flavus and A oryzae.