Evaluation of the Bruker Biotyper Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry System for Identification of Aspergillus Species Directly from Growth on Solid Agar Media

Introduction Invasive aspergillosis (IA) is a fungal infection that particularly affects immunocompromised hosts. Recently, several studies have indicated a high incidence of IA in intensive care unit (ICU) patients. However, few data are available on the epidemiology and outcome of patients with IA in this setting. Methods An observational study including all patients with a positive Aspergillus culture during ICU stay was performed in 30 ICUs in 8 countries. Cases were classified as proven IA, putative IA or Aspergillus colonization according to recently validated criteria. Demographic, microbiologic and diagnostic data were collected. Outcome was recorded 12 weeks after Aspergillus isolation. Results A total of 563 patients were included, of whom 266 were colonized (47%), 203 had putative IA (36%) and 94 had proven IA (17%). The lung was the most frequent site of infection (94%), and Aspergillus fumigatus the most commonly isolated species (92%). Patients with IA had higher incidences of cancer and organ transplantation than those with colonization. Compared with other patients, they were more frequently diagnosed with sepsis on ICU admission and more frequently received vasopressors and renal replacement therapy (RRT) during the ICU stay. Mortality was 38% among colonized patients, 67% in those with putative IA and 79% in those with proven IA (P < 0.001). Independent risk factors for death among patients with IA included older age, history of bone marrow transplantation, and mechanical ventilation, RRT and higher Sequential Organ Failure Assessment score at diagnosis. Conclusions IA among critically ill patients is associated with high mortality. Patients diagnosed with proven or putative IA had greater severity of illness and more frequently needed organ support than those with Aspergillus spp colonization.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is a powerful tool for the rapid and highly accurate identification of clinical pathogens but has not been utilized extensively in clinical mycology due to challenges in developing an effective protein extraction method and the limited databases available. Here, we developed an alternate extraction procedure and constructed a highly stringent database comprising 294 individual isolates representing 76 genera and 152 species. To our knowledge, this is the most comprehensive clinically relevant mold database developed to date. When challenged with 421 blinded clinical isolates from our institution, by use of the BioTyper software, accurate species-level (score of ≥ 2.0) and genus-level (score of ≥ 1.7) identifications were obtained for 370 (88.9%) and 18 (4.3%) isolates, respectively. No isolates were misidentified. Of the 33 isolates (7.8%) for which there was no identification (score of <1.7), 25 were basidiomycetes not associated with clinical disease and 8 were Penicillium species that were not represented in the database. Our library clearly outperformed the manufacturer's database that was obtained with the instrument, which identified only 3 (0.7%) and 26 (6.2%) isolates at species and genus levels, respectively. Identification was not affected by different culture conditions. Implementation into our routine workflow has revolutionized our mycology laboratory efficiency, with improved accuracy and decreased time for mold identification, eliminating reliance on traditional phenotypic features.