Infection and Drug Resistance (May 2023)
Performance of Two Matrix-Assisted Laser Desorption Ionization–Time-of-Flight Mass Spectrometry (MALDI-TOF MS) Systems for Identification of the Viridans Group Streptococci
Abstract
Fen Pan,1,2,* Na Zhao,3,* Wantong Zhao,1 Chun Wang,1 Yan Sun,1 Haomin Zhang,3 Juanxiu Qin,3 Qian Liu,3 Hong Zhang1,2 1Department of Clinical Laboratory, Shanghai Children’s Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, People’s Republic of China; 2Institute of Pediatric Infection, Immunity, and Critical Care Medicine, Shanghai Jiao Tong University School of Medicine, Shanghai, 200062, People’s Republic of China; 3Department of Laboratory Medicine, RenJi Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, People’s Republic of China*These authors contributed equally to this workCorrespondence: Hong Zhang, Department of Clinical Laboratory, Shanghai Children’s Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, People’s Republic of China, Tel +86 189 1712 8200, Email [email protected] Qian Liu, Department of Laboratory Medicine, RenJi Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, 200127, People’s Republic of China, Email [email protected]: 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, viridans group streptococci, identification, Streptococcus pneumoniae
