To investigate the application value of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) in rapid identification of clinical filamentous fungi.

The strains identified as filamentous fungi by morphology from January 2017 to January 2019 in Xuanwu Hospital of Capital Medical University were collected and identified by MALDI-TOF MS with the method of double formic acid sandwich and formic acid acetonitrile extraction. The results were compared with the results of its gene sequencing of polymerase chain reaction (PCR) in internal transcribed spacer (ITS). The distribution and source of filamentous fungi were analyzed.

A total of 90 clinical isolates of filamentous fungi were collected, including 70 strains of Aspergillus spp. (77.78%), 6 strains of Penicillium spp. (6.67%), 5 strains of Alternaria (5.56%), 4 strains of Fusarium spp. (4.44%), 2 strains of Sedosporium spp. (2.22%), 1 strain each of Rhizopus, Mucor and Trichoderma harzianum (1.11%). Aspergillus fumigatus (47 strains, 52.22%), Aspergillus flavus (13 strains, 14.44%) and Aspergillus niger (4 strains, 4.44%) were the main isolates. The specimens were mainly from respiratory tract (90.0%) (including sputum and alveolar lavage fluid), followed by cornea and ear canal secretion (3.33%), of which Aspergillus spp. were the mainly strains isolated from sputum samples (59 strains, 65.56%). Compared with the results of gene sequencing, the accuracy of MALDI-TOF MS was significantly higher than that of morphology (91.11% vs. 68.89%; χ² = 12.02, P = 0.01). MALDI-TOF MS was used to identify Aspergillus spp., Fusarium spp., Sedosporium spp. and Alternaria with high accuracy (98.57%-100%). The identification rates of filamentous fungi to species level were 91.11% (82/90) and 90% (81/90) by MALDI-TOF MS pretreated with dicarboxylic acid sandwich method and formic acid acetonitrile extraction method, and the identification rates of aspergillus species were 98.57% (69/70) and 97.14% (68/70), respectively. There was no significant difference in the identification accuracy of the two pretreatment methods (χ² = 0.34, P = 0.95). Both pretreatment methods could identify 100% Aspergillus fumigata, Aspergillus aflatus, Sedosporium and Alternaria spp. Among them, 89.36% (42/47) Aspergillus fumigatus and 76.92% (10/13) Aspergillus flavus scored ≥ 2.0.

The MALDI-TOF MS technique was rapid and accurate in the identification of filamentous fungi, and the double formic acid sandwich pretreatment method was more convenient and suitable for routine laboratory detection. It could be used for routine laboratory identification of common filamentous fungi such as Aspergillus.