Background: Reported literature on invasive group A streptococcal isolates in India is very scanty. This study was undertaken to determine the molecular heterogeneity of such isolates as seen in a tertiary care center.
Materials and methods: Thirty two blood culture isolates and 18 from other sterile body fluids were characterized by emm gene sequencing and multilocus sequence typing.
Results: Forty two emm types were identified including 25 from 32 blood isolates and 17 from 18 other body fluid isolates. Types 110, 74, 63, 85, 102, 105, 124 and st854.1 were common to both groups and accounted for 40% of the isolates. Two types namely, stKNB6 and stKNB9 were newly identified types. MLST identified forty eight sequence types (MLST - ST) of which 31 were from 32 blood isolates and 17 from 18 body fluid isolates; thirty three of them were hitherto unrecognized at the time of identification. Two blood isolates of emm 85 had the same MLST - ST 484 while three blood isolates of emm 110 had three different STs namely, ST 493, 494 and 497. Two types, ST 493 and ST497 had single locus variation while ST 497 had a double locus variation.
Conclusions: Our study shows that subtle allelic variations in the house keeping genes results in the development of new strains in a given emm type and contribute significantly to the existing high diversity of strains circulating in the community.