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Creation and validation of improved MALDI-TOF MS libraries for S. bovis-S. equinus-complex subspecies identification adapted to diagnostic culturing and extraction conditions

Öberg, Jonas LU orcid ; Engberg, Agnes ; Inghammar, Malin LU and Nilson, Bo LU orcid (2025) In Diagnostic Microbiology and Infectious Disease 113(3).
Abstract

Objectives: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) libraries have limited capabilities for identification of Streptococcus bovis/Streptococcus equinus-complex (SBSEC) subspecies. The objective was to develop and validate novel MALDI-TOF MS libraries adapted to diagnostic culturing and sampling conditions for improved identification of SBSEC subspecies. Methods: SBSEC isolates had previously been identified by whole genome sequencing, constituting the reference standard. Two libraries were constructed based on 53 isolates cultured on blood agar plates under aerobic conditions (SBSEC-CMRS-BAE) and on chocolate agar under anaerobic conditions (SBSEC[sbnd]CMRS-CAN). The performances of... (More)

Objectives: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) libraries have limited capabilities for identification of Streptococcus bovis/Streptococcus equinus-complex (SBSEC) subspecies. The objective was to develop and validate novel MALDI-TOF MS libraries adapted to diagnostic culturing and sampling conditions for improved identification of SBSEC subspecies. Methods: SBSEC isolates had previously been identified by whole genome sequencing, constituting the reference standard. Two libraries were constructed based on 53 isolates cultured on blood agar plates under aerobic conditions (SBSEC-CMRS-BAE) and on chocolate agar under anaerobic conditions (SBSEC[sbnd]CMRS-CAN). The performances of the new libraries, the Bruker MALDI Biotyper (MBT) Compass Library and the previously developed SBSEC[sbnd]CMRS library based on isolates cultured in brain heart infusion-broth, were validated with 119 unique isolates. Each isolate was sampled using the direct transfer, on-target extraction, and full extraction methods under the two different culture conditions – in total 714 different isolates and conditions. Results: With a cutoff identification score of ≥2.0, the MBT compass library identified subspecies in 463/714 (65 %) in total for all culturing conditions and methods, while the broth-based SBSEC[sbnd]CMRS library identified 674/698 (97 %). The novel SBSEC-CMRS-BAE and SBSEC[sbnd]CMRS-CAN libraries identified subspecies in 707/713 (99 %) and 684/706 (97 %), respectively. The SBSEC-CMRS-BAE library performed best, regardless of the culturing conditions used or the three sample preparation methods employed, with up to 100 % correct subspecies identifications. Conclusions: The novel SBSEC-CMRS-BAE library performed excellently and improved MALDI-TOF MS performance in identifying SBSEC subspecies. It can be implemented directly into routine clinical practice where the Bruker MALDI Biotyper is used.

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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
MALDI-TOF MS, Streptococcus bovis, Streptococcus gallolyticus ssp. gallolyticus, Streptococcus gallolyticus ssp. pasteurianus, Streptococcus lutetiensis, Streptocovccus infantarius, Subspecies identification
in
Diagnostic Microbiology and Infectious Disease
volume
113
issue
3
article number
117000
publisher
Elsevier
external identifiers
  • pmid:40674986
  • scopus:105010474666
ISSN
0732-8893
DOI
10.1016/j.diagmicrobio.2025.117000
project
Streptococcus bovis och gastrointestinal cancer: Epidemiologi, etiologi och diagnostik
language
English
LU publication?
yes
additional info
Publisher Copyright: © 2025 The Author(s)
id
851a0e9a-19c0-4da3-8bd5-01aad1eafeb5
date added to LUP
2025-07-22 14:36:24
date last changed
2025-07-24 03:21:02
@article{851a0e9a-19c0-4da3-8bd5-01aad1eafeb5,
  abstract     = {{<p>Objectives: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) libraries have limited capabilities for identification of Streptococcus bovis/Streptococcus equinus-complex (SBSEC) subspecies. The objective was to develop and validate novel MALDI-TOF MS libraries adapted to diagnostic culturing and sampling conditions for improved identification of SBSEC subspecies. Methods: SBSEC isolates had previously been identified by whole genome sequencing, constituting the reference standard. Two libraries were constructed based on 53 isolates cultured on blood agar plates under aerobic conditions (SBSEC-CMRS-BAE) and on chocolate agar under anaerobic conditions (SBSEC[sbnd]CMRS-CAN). The performances of the new libraries, the Bruker MALDI Biotyper (MBT) Compass Library and the previously developed SBSEC[sbnd]CMRS library based on isolates cultured in brain heart infusion-broth, were validated with 119 unique isolates. Each isolate was sampled using the direct transfer, on-target extraction, and full extraction methods under the two different culture conditions – in total 714 different isolates and conditions. Results: With a cutoff identification score of ≥2.0, the MBT compass library identified subspecies in 463/714 (65 %) in total for all culturing conditions and methods, while the broth-based SBSEC[sbnd]CMRS library identified 674/698 (97 %). The novel SBSEC-CMRS-BAE and SBSEC[sbnd]CMRS-CAN libraries identified subspecies in 707/713 (99 %) and 684/706 (97 %), respectively. The SBSEC-CMRS-BAE library performed best, regardless of the culturing conditions used or the three sample preparation methods employed, with up to 100 % correct subspecies identifications. Conclusions: The novel SBSEC-CMRS-BAE library performed excellently and improved MALDI-TOF MS performance in identifying SBSEC subspecies. It can be implemented directly into routine clinical practice where the Bruker MALDI Biotyper is used.</p>}},
  author       = {{Öberg, Jonas and Engberg, Agnes and Inghammar, Malin and Nilson, Bo}},
  issn         = {{0732-8893}},
  keywords     = {{MALDI-TOF MS; Streptococcus bovis; Streptococcus gallolyticus ssp. gallolyticus; Streptococcus gallolyticus ssp. pasteurianus; Streptococcus lutetiensis; Streptocovccus infantarius; Subspecies identification}},
  language     = {{eng}},
  number       = {{3}},
  publisher    = {{Elsevier}},
  series       = {{Diagnostic Microbiology and Infectious Disease}},
  title        = {{Creation and validation of improved MALDI-TOF MS libraries for S. bovis-S. equinus-complex subspecies identification adapted to diagnostic culturing and extraction conditions}},
  url          = {{http://dx.doi.org/10.1016/j.diagmicrobio.2025.117000}},
  doi          = {{10.1016/j.diagmicrobio.2025.117000}},
  volume       = {{113}},
  year         = {{2025}},
}