Performance of Two Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) Systems for Identification of the Viridans Group Streptococci

Fen Pan; Na Zhao; Wantong Zhao; Chun Wang; Yan Sun; Haomin Zhang; Juanxiu Qin; Qian Liu; Hong Zhang

doi:10.2147/IDR.S407667

Performance of Two Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) Systems for Identification of the Viridans Group Streptococci

Infect Drug Resist. 2023 May 10:16:2901-2909. doi: 10.2147/IDR.S407667. eCollection 2023.

Authors

Fen Pan^#^{1

2}, Na Zhao^#³, Wantong Zhao¹, Chun Wang¹, Yan Sun¹, Haomin Zhang³, Juanxiu Qin³, Qian Liu³, Hong Zhang^{1

2}

Affiliations

¹ Department of Clinical Laboratory, Shanghai Children's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, People's Republic of China.
² Institute of Pediatric Infection, Immunity, and Critical Care Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, 200062, People's Republic of China.
³ Department of Laboratory Medicine, RenJi Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, People's Republic of China.

^# Contributed equally.

Abstract

Background: Due to similar colony morphology among viridans group streptococci (VGS), the differentiation of VGS species remains difficult in routine clinical microbiology. Recently, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) has been described as a fast method for identifying various bacteria at species level, and also for the VGS strains.

Methods: A total of 277 VGS isolates were identified with the two MALDI-TOF MS systems (VITEK MS and Bruker Biotyper). The tuf and rpoB gene sequencing was used as the reference identification method for comparison.

Results: Based on tuf and rpoB gene sequencing, 84 isolates were S. pneumoniae and 193 strains were other VGS isolates including S. anginosus group (n=91, 47.2%), S. mitis group (n=80, 41.5%), S. bovis group (n=11, 5.7%), S. salivarius group (n=10, 5.2%), and S. mutans group (n=1, 0.5%). VITEK MS and Bruker Biotyper accurately identified 94.6% and 89.9% of all VGS isolates, respectively. VITEK MS showed better identification results than Bruker Biotyper for S. mitis group including S. pneumoniae and S. bovis group, but for other VGS isolates, two MALDI-TOF MS systems showed comparable identification performance. However, VITEK MS was able to identify S. gallolyticus to the subspecies level with high-confidence (S. gallolyticus ssp. pasteurianus), while the Bruker Biotyper system could not. While Bruker Biotyper system could be able to correctly differentiate the subspecies of S. salivarius from S. vestibularis, VITEK MS poorly identify.

Conclusion: This study demonstrated that two MALDI-TOF MS systems allowed discrimination for most VGS isolates with different identification performance, but Bruker Biotyper could produce more misidentifications and VITEK MS system. It is crucial to be familiar with the performance of MALDI-TOF MS systems used in clinical microbiology.

Keywords: MALDI-TOF MS; Streptococcus pneumoniae; identification; viridans group streptococci.

Grants and funding

This work was supported by the foundation of Shanghai Municipal Key Clinical Specialty (shslczdzk06902), Shanghai Municipal Commission of Health and Family Planning (201940253), and Shanghai “Rising Stars of Medical Talents” Youth Development Program (Youth Medical Talents –Clinical Laboratory Practitioner Program).