ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Infectious Agents and Disease
Raman signatures of Cnm-positive Streptococcus mutans: II, Screening the virulence of clinical isolates
Giuseppe Pezzotti 1,2,3,4,5
Tetsuya Adachi 2,6
Kazunori Kitagawa 7,8
Saki Ikegami 6,7
Hayata Imamura 3,7
Toshiro Yamamoto 9
Kazu Okuma 6
Yoshiyuki Matsuo 10
Wenliang Zhu 7
Yoshiki Yasukochi 8
Koichiro Higasa 8
Saki Nishihama 11
Katsuhiro Takeda 11
Hideki Shiba 11
Miki Kawada-Matsuo 12
Hitoshi Komatsuzawa 12
1. Biomedical Engineering Center, Kansai Medical University, Hirakata, Japan
2. Department of Immunology, Graduate School of Medical Science; Department of Dental Medicine, Graduate School of Medical Science, Kyoto Furitsu Ika Daigaku, Kyoto, Japan
3. Department of Orthopedic Surgery, Tokyo Ika Daigaku, Shinjuku, Japan
4. Department of Applied Science and Technology,, Politecnico di Torino, Turin, Italy
5. Department of Molecular Science and Nanosystems, Universita Ca' Foscari, Venice, Italy
6. Department of Microbiology, Kansai Ika Daigaku, Hirakata, Japan
7. Ceramic Physics Laboratory, Kyoto Kogei Sen'i Daigaku, Kyoto, Japan
8. Genome Analysis, Institute of Biomedical Science, Kansai Ika Daigaku, Hirakata, Japan
9. Department of Dental Medicine, Graduate School of Medical Science, Kyoto Furitsu Ika Daigaku, Kyoto, Japan
10. Central Research Center, Institute of Biomedical Science, Kansai Ika Daigaku, Hirakata, Japan
11. Department of Biological Endodontics Graduate School of Biomedical & Health Sciences, Hiroshima Daigaku, Higashihiroshima, Japan
12. Department of Bacteriology, Graduate School of Biomedical & Health Sciences, Hiroshima Daigaku, Higashihiroshima, Japan
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Abstract
This study dealt with developing a Raman spectroscopic method for estimating the degree of virulence of Streptococcus mutans bacteria isolated from clinical swab samples. Raman experiments aimed at es-tablishing suitable spectroscopic parameters to quantify bacterial virulence and were conducted on a limited series of six clinical iso-lates three of which were genomically classified as Cnm-positive and three as Cnm-negative. Samples were characterized after biofilm purification and compared with cultures of the same bacteria in physiological state of equilibrium, namely, after long-term stabilization in vitro. Statistically significant series of ten Raman spectra were collected at different locations on each clinical sample, and their averag-es interpreted as multiomic snapshots of bacterial structure. Building upon the spectroscopic analyses described in the companion paper Part I, Raman characterizations of clinical isolates revealed a significant degree of variability in the bacterial structure, but also suggest-ed clear classification criteria for clinical samples. These spectroscopic criteria reflected specific biochemical circumstances affecting the structure of bacteria in their pathophysiological state. Raman algo-rithms based on the fractional balance between proteins and pepti-doglycans, and the degree of protein structural disorder vs. presence of oxysulfur compounds enabled insightful classifications of bacterial virulence, which matched genomic analyses. These structural charac-teristics, which allowed distinguishing between Cnm-positive and Cnm-negative bacteria, could provide fast and unbiased diagnostic criteria for risk assessments of endocarditis and hemorrhagic strokes as induced by Cnm-positive bacteria. In summary, the present study proposes a new spectroscopic approach to oral flora-related diagnostics and confirms the potential utility of Raman spectroscopy in chairside analyses of clinical isolates.
Summary
Keywords
Clinical Isolates, Cnm protein, Raman algorithms, Streptococcus mutans, Virulence
Received
09 January 2026
Accepted
18 February 2026
Copyright
© 2026 Pezzotti, Adachi, Kitagawa, Ikegami, Imamura, Yamamoto, Okuma, Matsuo, Zhu, Yasukochi, Higasa, Nishihama, Takeda, Shiba, Kawada-Matsuo and Komatsuzawa. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Giuseppe Pezzotti; Hitoshi Komatsuzawa
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