Chung Ang Ma University researchers

Image: The sensitivity and accuracy of three MALDI-TOF MS approaches for the identification of filamentous fungi was determined by researchers from Chung-Ang University.
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Credit: Professor Mi Kyung Lee of Chung-Ang University

In recent years, fungi or filamentous molds have emerged as causative agents of life-threatening infections in immunocompromised individuals. Timely management of this infection requires prompt and accurate diagnosis of mold in clinical settings.

Unfortunately, traditional methods are very time consuming, due to the long incubation times required to grow and screen the molds. On the other hand, advanced molecular techniques are more sensitive and efficient. One such technique that can detect filamentous fungal isolates with high sensitivity and reproducibility, is Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). It can differentiate between samples based on differences in mass and charge. However, it is not widely used due to limitations in database availability and lack of standardized procedures.

Recently, a team of researchers from Chung-Ang University in the Republic of Korea led by Professor Mi-Kyung Lee evaluated three different MALDI-TOF MS approaches used in local clinical settings, to identify templates.

In their study published in Journal of Clinical Microbiology On October 26, 2022, they compared the diagnostic performance and accuracy of Bruker Biotyper, ASTA MicroIDSys, and Vitek MS. They also evaluated the sensitivity of three processing methods – ‘direct’, ‘on plate’ and ‘in tube’ – using 84 filamentous fungal isolates.

Professor Lee explains the rationale behind their study, “Choosing an appropriate sample preparation method can improve the efficiency and accuracy of mold identification. In addition, the development of systematic processes at the diagnostic level can ultimately contribute to effective treatments for patients.”

The study found that Bruker Biotyper correctly identified 71.43% of isolates down to the species or genus level, while ASTA MicroIDSys and Vitek MS showed accuracy rates of 70.24% and 55.95%, respectively. Moreover, the direct method of sample preparation was favorable over the other two methods, due to its simplicity and ease of application. Notably, the identification sensitivity did not differ significantly across the different sample preparation methods.

The rate of misidentification is an important consideration in clinical laboratories because it can lead to inappropriate treatment interventions for patients. In this study, one isolate was misidentified using the Vitek-MS with plate method. Further, specify the level of species Aspergillus fungus (highly prevalent and clinically significant microorganism) was highest by Vitek-MS, indicating the applicability of this technique in clinical settings.

The number of incorrectly identified species was 17, 15 and 23 by Bruker Biotyper, ASTA MicroIDSys and Vitek MS, respectively. The team suggested that additional evaluations would be needed if an error in identification occurred due to a lack of a particular species in the library rather than an error. Furthermore, the team determined that any differences in sensitivity could be attributed to differences in the system’s databases.

In summary, MALDI-TOF MS is a valuable technology that can accurately and timely identify clinically important microorganisms. Standardization of processes and guidelines that can be applied to a wide variety of species can help reduce the process bias that occurs through these technologies. In addition, limitations regarding acquisition parameters, matrix quality, and devices require further evaluations.

When asked about the applications of the study, Professor Lee said, “Our study is the first to compare the sensitivity and accuracy of three MALDI-TOF MS tools as well as the effectiveness of three processing methods for the identification of filamentous fungi. Accurate results obtained through a simple and streamlined process of mold identification using MALDI-TOF MS can improve the efficiency of the users’ laboratory work and the efficiency of treatment for patients.”

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Reference

DOI: https://doi.org/10.1128/jcm.00812-22

Authors: Yoojeong ChoiaAnd Daewon KimBKiwon ChoiaHyukmin LeecJae Suk KimDrJeong Yil AhnBand Mi Kyung Leea

Affiliations:

aDepartment of Laboratory Medicine, Chung-Ang University College of Medicine, Seoul, Republic of Korea

BDepartment of Laboratory Medicine, Gachon University Gil Medical Center, Incheon, Republic of Korea

cDepartment of Laboratory Medicine and Institute for Bacterial Resistance Research, Yonsei University College of Medicine, Seoul, Republic of Korea

DrDepartment of Laboratory Medicine, Gangdong Sacred Heart Hospital, Hallym University College of Medicine, Seoul, Republic of Korea

About Chung-Ang University

Chung-Ang University is a private comprehensive research university located in Seoul, South Korea. It began as a kindergarten in 1916 and attained university status in 1953. It is fully accredited by the Ministry of Education of Korea. Chung-Ang University conducts research activities under the motto “Justice and Truth”. Its new vision of completing 100 years is “Global Creative Leader”. Chung-Ang University offers undergraduate, graduate, and doctoral programs, which include the Faculty of Law, the Management Program, and the Faculty of Medicine; It has 16 undergraduate and graduate schools each. Chung-Ang University’s arts and culture programs are among the best in Korea.

Website: https://neweng.cau.ac.kr/index.do

About Professor Mi Kyung Lee of Chung-Ang University

Dr. Mi Kyung Lee is a professor in the Department of Laboratory Medicine at Chung-Ang University College of Medicine. She holds a PhD in Laboratory Medicine and has more than 230 publications to her credit. With over two decades of research experience in the fields of clinical microbiology and molecular genetics, her current research focus is on fungal infections and antifungal drug susceptibility. With the support of the Korea Science and Engineering Foundation, she successfully completed a one-year training fellowship in the Fungal Disease Branch, Centers for Disease Control and Prevention in Atlanta, GA, USA in 2002, after which she continuously performs epidemiological and molecular studies of clinical microorganisms (Especially candida species) in South Korea.


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