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

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.

Streptococcus gordonii‐associated infective endocarditis: Case series, literature review, and genetic study

“…It is also worth noting that matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) has demonstrated to accurately identify viridans streptococci within the sanguinis group to the species level unlike the S. mitis group. 24 The in-hospital mortality for VGS-related IE ranges from 10% to 29%, depending on patient characteristics and complications. 8 The treatment of choice for highly penicillin-susceptible S. gordonii native valve endocarditis is a 4-week regimen of parenteral penicillin or ceftriaxone.…”

Challenging Diagnosis of Streptococcus intermedius-Associated Empyema in an Immunocompetent Adult: A Case Report and Literature Review

“…Consequently, species-specific PCR that targets genes such as ily, which is unique to S. intermedius, is considered the gold standard. Moreover, advanced techniques like matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry also offer rapid and precise species-level identification, as demonstrated in our patient who was identified through sequencing and MALDI-TOF [ 9 ].…”