Distribution of small native plasmids in Streptococcus pyogenes in India

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Streptococcus pyogenes is a significant human pathogen.
• Understanding circulating plasmids is crucial for characterizing bacterial populations.
• India has high diversity of S. pyogenes strains and infection rates.

Purpose of the Study:

• To determine the distribution of small plasmids (<5kb) in S. pyogenes isolates from India.
• To characterize novel plasmid subtypes and their genetic elements.
• To investigate the potential role of plasmids in S. pyogenes evolution and prevalence.

Main Methods:

• Developed and utilized PCR assays for plasmid replication initiation protein, repressor, and bacteriocin genes.
• Sequenced representative plasmids of novel subtypes.
• Analyzed plasmid distribution across 77 emm-types in 279 S. pyogenes isolates.

Main Results:

• Identified four distinct small plasmid subtypes, two of which are previously unknown (pA852 and pA996).
• pA852 and pA996 belong to the pMV158 and pC194/pUB110 rolling-circle plasmid families, respectively.
• Newly characterized subtypes (pA852-like and pA996-like) constituted 42% and 22% of detected plasmids, respectively.
• No antibiotic resistance genes were found; all plasmids carried bacteriocin genes.
• pA852-like plasmids were prevalent in the most common emm-type 11.0.

Conclusions:

• Novel small plasmids are widespread in Indian S. pyogenes populations.
• Bacteriocin genes on these plasmids may confer a fitness advantage to S. pyogenes.
• The prevalence of emm-type 11.0 may be linked to intrinsic fitness and plasmid acquisition.