Discrimination of Streptococcus equi subsp. equi and Streptococcus equi subsp. zooepidemicus using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

This study investigates the use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in identifying two subspecies of the bacterium Streptococcus equi, which cause severe diseases in horses. The findings show that the method can accurately identify these subspecies and potentially improve disease diagnosis and treatment.

Background and Objective

• This research primarily aims to accurately and promptly identify Streptococcus equi subspecies: S. equi subsp. equi and S. equi subsp. zooepidemicus which are responsible for a severe contagious disease in horses, known as strangles. The authors propose that the quality and speed of this identification process could greatly improve veterinary microbiology, disease diagnosis, and treatment.

Methods

• The authors utilized an advanced analytical technology called matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). They evaluated this technique by comparing it to an automated biochemical system.
• A total of 50 clinical isolates – 25 from each subspecies of S. equi – were analyzed using this MALDI-TOF MS platform.

Results and Findings

• The MALDI-TOF MS platform was capable of identifying all 50 isolates accurately to the species level. Moreover, unique mass peaks in the bacterial peptide mass spectra were observed, which could be used to accurately distinguish between the subspecies of S. equi.
• S. equi subsp. equi and S. equi subsp. zooepidemicus had unique mass peaks at 6,751.9 ± 1.4 (mean ± standard deviation) and 5,958.1 ± 1.3, respectively.
• The automated biochemical system correctly identified 47 out of 50 isolates at the species level and 46 out of 50 at the subspecies level. It confirms MALDI-TOF MS’s superiority in terms of precision and reliability.

Conclusion

• Based on the research findings, the authors concluded that MALDI-TOF MS could be an effective method for identifying not only the S. equi species but also its subspecies. This accuracy is crucial for correct and fast diagnosis and treatment of equine diseases caused by these bacteria.