Automated classification of group B Streptococcus into different clonal complexes using MALDI-TOF mass spectrometry.

Area of Science:

• Microbiology
• Mass Spectrometry
• Clinical Diagnostics

Background:

• Group B Streptococcus (GBS) is a significant pathogen, and its accurate identification and subtyping are crucial for clinical management.
• Current methods for GBS classification into clonal complexes (CCs) can be labor-intensive and may lack automation.
• Matrix-Assisted Laser Desorption/Ionization Time-of Flight Mass Spectra (MALDI-TOF MS) is a rapid identification technique with potential for further discriminatory applications.

Purpose of the Study:

• To evaluate the performance of MALDI-TOF MS for the automated classification of GBS into five major clonal complexes (CCs).
• To compare the efficacy of two MALDI-TOF MS-based subtyping methods: main spectrum (MSP) and MSP-M.

Main Methods:

• MALDI-TOF MS analysis was performed on 167 GBS strains from five major CCs (CC10, CC12, CC17, CC19, CC23).
• A reference set (n=67) and a validation set (n=100) were used for developing and evaluating GBS CCs subtyping MSP and MSP-M using MALDI BioTyper and ClinProTools.
• GBS CCs subtyping MSP-M was generated by optimizing discriminative peaks based on an informative classification model.

Main Results:

• The positive predictive value (PPV) for GBS CCs subtyping MSP-M was higher than MSP for CC10 (99.21% vs. 93.65%).
• PPVs were similar for CC12, CC17, and CC19, but lower for CC23 using MSP-M compared to MSP.
• Overall, MALDI-TOF MS demonstrated potential for automated GBS CC categorization.

Conclusions:

• MALDI-TOF MS is a promising tool for the automated categorization of GBS into five major CCs using both MSP and MSP-M.
• The GBS CCs subtyping MSP-M method is preferred for accurate prediction, particularly for CCs with highly discriminative peaks.
• Further refinement of MALDI-TOF MS methods could enhance routine GBS identification and subtyping capabilities.