Genetic diversity and allelic variation in south Indian isolates of Group A streptococci causing invasive disease

Area of Science:

• Microbiology
• Molecular Epidemiology
• Infectious Diseases

Background:

• Invasive Group A Streptococcus (iGAS) infections are a significant public health concern.
• Literature on iGAS isolates in India is limited, necessitating further investigation.
• This study addresses the molecular characterization of iGAS in a tertiary care center in India.

Purpose of the Study:

• To determine the molecular heterogeneity of invasive Group A Streptococcus isolates in India.
• To identify prevalent emm types and multilocus sequence types (MLST) among iGAS isolates.
• To understand the genetic diversity and strain evolution within iGAS populations.

Main Methods:

• emm gene sequencing was performed on 32 blood isolates and 18 isolates from other sterile body fluids.
• Multilocus Sequence Typing (MLST) was employed to further characterize the genetic relatedness of the isolates.
• Isolates were obtained from a tertiary care center, providing a clinical context for the study.

Main Results:

• Forty-two distinct emm types were identified, with 25 found in blood isolates and 17 in other body fluid isolates.
• Common emm types included 110, 74, 63, 85, 102, 105, 124, and st854.1, accounting for 40% of isolates.
• MLST identified 48 sequence types (STs), with 33 being previously unrecognized, highlighting significant genetic diversity.

Conclusions:

• Subtle allelic variations in housekeeping genes contribute to the emergence of new strains within existing emm types.
• These variations play a significant role in the high diversity of circulating iGAS strains in the community.
• The findings underscore the importance of molecular surveillance for understanding iGAS epidemiology in India.