Assessment of two multilocus sequence typing (MLST) schemes available for Streptococcus mutans

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Two multilocus sequencing typing (MLST) schemes exist for Streptococcus mutans: Nakano (2007, 8 genes) and Do (2010, 6 housekeeping + 2 virulence genes).
• These schemes are used for bacterial genotyping and understanding population structures.

Purpose of the Study:

• To compare the discriminatory power and congruence of the two available MLST schemes for Streptococcus mutans.
• To evaluate their utility in validating repetitive extragenic palindromic polymerase chain reaction (rep-PCR) genotypes.

Main Methods:

• Thirty-three S. mutans isolates from 11 rep-PCR genotype groups were subjected to MLST using both schemes.
• Sequencing, PubMLST database comparison for allelic and sequence type (ST) assignment, and phylogenetic analysis were performed.
• Discriminatory power, congruence, and convenience were assessed.

Main Results:

• No significant difference in discriminatory power was found between the Nakano and Do MLST schemes for S. mutans.
• Both MLST schemes demonstrated consistent clonal clusters and were congruent with rep-PCR genotypes.
• MLST showed marginally higher discriminatory power than rep-PCR.
• New alleles and STs were identified and submitted to the PubMLST database.

Conclusions:

• Both MLST schemes are well-designed and exhibit similar genotype discrimination capabilities for S. mutans.
• The findings support the clonality of S. mutans genotypes across unrelated subjects.
• Either MLST scheme can be effectively used to verify rep-PCR genotypes.