Schemes and Performance Evaluation Criteria of Korean Association of External Quality Assessment (KEQAS) for Improving Laboratory Testing
2021; 41(2): 230-239
Ann Lab Med 2021; 41(2): 214-220
Published online March 1, 2021 https://doi.org/10.3343/alm.2021.41.2.214
Copyright © Korean Journal of Laboratory Medicine.
Ju Hyeon Shin, M.D.1 , Soo Hyun Kim, M.D.1,2 , Dain Lee, M.S.1 , Seung Yeob Lee, M.D.1 , Sejong Chun, M.D.1 , Jun Hyung Lee, M.D.1 , Eun Jeong Won, M.D.1,3 , Hyun Jung Choi, M.D.1 , Hyun Woo Choi, M.D.1 , Seung Jung Kee, M.D.1 , Myung Geun Shin, M.D.1 , and Jong Hee Shin, M.D.1
1Department of Laboratory Medicine, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Korea; 2Department of Microbiology, Chonnam National University Medical School, Hwasun, Korea; 3Department of Parasitology and Tropical Medicine, Chonnam National University Medical School, Hwasun, Korea
Correspondence to: Soo Hyun Kim, M.D.
Department of Laboratory Medicine, Chonnam National University Hwasun Hospital, 322 Seoyang-ro, Hwasun-eup, Hwasun-gun, Jeollanam-do 58128, Korea
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
The correct identification of filamentous fungi is challenging. We evaluated the performance of the VITEK MS v3.0 system (bioMérieux, Marcy-l’Étoile, France) for the identification of a wide spectrum of clinically relevant filamentous fungi using a Korean collection. Strains that were added to the upgraded v3.2 database were additionally identified by the VITEK MS v3.2 system. Of the 105 tested isolates, including 37 Aspergillus (nine species), 41 dermatophytes (seven species), and 27 other molds (17 species), 43 (41.0%) showed “no identification” or “multiple species identification” results at the initial VITEK MS testing; these isolates were retested using the same method. Compared with sequence-based identification, the correct identification rate using VITEK MS for Aspergillus, dermatophytes, other molds, and total mold isolates was 67.6%, 56.1%, 48.1%, and 58.1% at the initial testing and 94.6%, 78.0%, 55.6%, and 78.1% with retesting, respectively. Following retesting, 19 (18.1%) and two (1.9%) isolates showed “no identification” and “misidentification” results, respectively. VITEK MS reliably identified various filamentous fungi recovered in Korea, with a very low rate of misidentification.
Keywords: Filamentous fungi, Mass spectrometry, VITEK MS, Aspergillus, Dermatophytes, Evaluation, Performance, Identification
Fungi have increasingly been shown to cause various serious infections owing to the growing number of immunocompromised patients receiving chemotherapy, immunosuppressive agents, or medical intervention [1-3].
MALDI-TOF MS VITEK MS (bioMérieux, Marcy-l’Étoile, France) recently introduced an update of its knowledge base version 3.0 (v3.0) database, version 3.2 (v3.2). To date, only three studies have evaluated the performance of VITEK MS v3.0 system for the identification of filamentous fungi, showing that it may be influenced by the examined species distribution [6-8]. Furthermore, in contrast to the study by Rychert,
All 105 filamentous fungi isolates were obtained from 12 Korean hospitals from 2016 to 2019, and duplicate isolates were excluded. Isolates were recovered from skin/tissue (N = 48), wound/pus (N = 22), respiratory specimens (N = 21), body fluids (N = 4), and other non-sterile specimens (N = 10). After sequencing the internal transcribed spacer or D1/D2 region of the 28S ribosomal DNA with additive sequencing of β-tubulin or calmodulin genes for
The VITEK MS results were compared with the sequence-based identification results and assigned to one of the four categories: (i) correct identification (identical to sequence-based identification), (ii) incomplete identification (either only the genus level was correctly identified or two or more species were proposed and one was correct), (iii) misidentification (none of the proposed species were correct), or (iv) no identification. As VITEK MS only displays species-complex-level identifications for some species, these were considered as the correct identification. McNemar’s, chi-square, and Fisher’s exact tests were performed to compare the correct identification rates. IBM SPSS Statistics for Windows version 25.0 (IBM Corp., Armonk, NY, USA) was used, and
Table 1 shows the results of 105 clinical filamentous fungi isolates identified using VITEK MS. At the initial testing, VITEK MS correctly identified 67.6% of
Of the 33 species tested in this study,
According to three recent studies on the performance evaluation of VITEK MS v3.0 system for identification of filamentous fungi, the correct identification rate varied, ranging from 51.0% to 91.3%, most likely owing to the different composition of the tested isolates in each study [6-8]. In the present study, for all 105 filamentous fungi isolates representing commonly isolated species from Korean hospitals, the correct identification rate was 58.1% at the initial testing and 78.1% with retesting using VITEK MS v3.0 and v3.2 systems. The correct identification rate of dermatophytes was 78.0%, like the previous finding (84.5%) . In line with previous studies [7, 8], retesting filamentous fungi isolates improved the correct identification rate, indicating the necessity for retesting. The reasons for the improvement following retesting are poorly understood; however, they may be attributed to the characteristics of the filamentous fungi. In contrast to bacteria, it can be difficult to obtain uniform conidia for testing from filamentous fungi colonies on solid media, depending on culture conditions. However, given the fact that misidentification rate was only 1.9%, filamentous fungi isolates that remain unidentified after repeated VITEK MS testing can be further evaluated by sequence analysis or other morphological evaluation without the risk of misidentification.
The detailed VITEK MS retesting results for the 43 isolates, including 12
VITEK MS correctly identified commonly isolated
This study represents the first performance evaluation of the VITEK MS v3.0 system for the identification of clinically relevant filamentous fungi using the Korean collection, some of which were supplemented by the VITEK MS v3.2 system. VITEK MS provided 94.6% and 78.0% correct identification rates for
We thank Jong Soo Choi and Yong Jun Bang from the Institute of Medical Mycology, Catholic Skin Clinic, Daegu, Korea for kindly providing dermatophyte isolates.
JHS1 and DL performed the experiments. SHK supervised the experiments. SYL, SC, JHL, EJW, HJC, HWC, SJK, SHK, MGS, and JHS2 provided advice regarding interpretation. JHS1 and SHK wrote the manuscript. SHK was responsible for conceiving this study and provided critical contributions to this manuscript. All authors provided critical feedback and approved the final manuscript.
No potential conflicts of interest relevant to this paper were reported