Assignment of Streptococcus agalactiae isolates to clonal complexes using a small set of single nucleotide...

Area of Science:

• Microbiology
• Genetics
• Epidemiology

Background:

• Streptococcus agalactiae (Group B Streptococcus, GBS) is a significant human pathogen, especially impacting newborns.
• The need for efficient GBS typing methods is increasing due to evidence linking genotype to virulence.
• Current typing methods require refinement for accurate population structure analysis.

Purpose of the Study:

• To develop a novel single nucleotide polymorphism (SNP) based method for GBS typing.
• To assign GBS isolates to established multilocus sequence typing (MLST)-defined clonal complexes.
• To create a high-throughput, cost-effective GBS genotyping tool.

Main Methods:

• Utilized the "Not-N" bioinformatic algorithm for identifying diagnostic SNPs.
• Developed a five-SNP set through empirical testing and analysis of MLST data.
• Applied kinetic Polymerase Chain Reaction (PCR) for SNP interrogation in 116 GBS isolates.

Main Results:

• An initial SNP set showed poor resolution due to low diversity and high horizontal gene transfer.
• The refined five-SNP set successfully divided GBS into 10 groups, aligning with population structure.
• A fifth SNP improved detection of the clinically important clonal complex 17 to 100% sensitivity.

Conclusions:

• A robust five-SNP genotyping method for GBS has been established.
• This method provides biologically valid groupings suitable for high-throughput surveillance.
• The SNP method can be combined with other loci for enhanced genetic resolution when needed.