Understanding the viridians group streptococci: Are we there yet?

Area of Science:

• Microbiology
• Genetics
• Clinical Diagnostics

Background:

• Viridans group streptococci are commensals causing opportunistic infections in immunocompromised patients.
• Phenotypic variability complicates accurate species differentiation, impacting clinical management.
• Traditional methods like Facklam's typing scheme have limitations in resolving species ambiguity.

Purpose of the Study:

• To evaluate the efficacy of molecular methods for accurate identification of viridans group streptococci.
• To compare genotypic approaches with established phenotypic typing schemes.
• To establish a reliable method for characterizing large bacterial isolate collections.

Main Methods:

• Nucleic acid-based methods, including 16S rRNA and sodA gene sequencing.
• Multilocus sequence analysis (MLSA) of seven house-keeping genes (map, pfl, pyk, ppaC, rpoB, sodA, and tuf).
• Polymerase chain reaction (PCR) amplification for gene sequencing.

Main Results:

• Genotypic methods, particularly sequencing of 16S rRNA and sodA genes, show promising results for bacterial identification.
• MLSA of seven house-keeping genes provides accurate species differentiation for viridans group streptococci.
• MLSA is a viable and accurate alternative to phenotypic methods for bacterial characterization.

Conclusions:

• Molecular techniques offer superior accuracy for viridans group streptococci identification compared to phenotypic methods.
• MLSA is a robust tool for the precise classification of these clinically significant bacteria.
• Accurate identification is crucial for understanding the pathogenicity and managing infections caused by viridans group streptococci.