Molecular epidemiology and virulence characteristics of prevalent group A streptococci recovered from patients in northern India

Abstract

Introduction: In this study, the prevalence of M types of Group A Streptococcus (GAS) in North India, invasive behavior of prevalent M types, and inflammatory immune response by host cells were studied.

Methodology: A total of 1,047 clinical samples were collected between 2004 and 2010. Confirmation of GAS was determined by serotyping and M types were identified by emm gene sequencing. The most prevalent serotypes were selected to study their invasive behavior and inflammatory immune response under different temperatures and salt concentrations in A549 and HEp-2 cells.

Results: Ninety-two isolates were identified as GAS of which 17 were M types with 18.5% heterogeneity. The most prevalent M types were M1 (21.73%) and M49 (8.7%), respectively. M1 and M49 were used to study virulence potential and inflammatory immune responses. The efficiency of cell infection decreased with increased temperature for both M types, increasing with lowering temperatures compared to the uninfected control (37°C). As salt concentration was increased, cell infection efficiency was lowered with some exceptions; the infection efficiency of M1 strain in A549 cells with 0.6 M NaCl was 50 fold higher (p ≤ 0.03). Significantly increased production of IL-6 and IL-8 was observed in both cell lines infected with GAS and when grown under different environmental conditions compared to uninfected cell lines.

Conclusions: This study determined the prevalence of different M types in North India and showed that environmental conditions can regulate cell infection by GAS . This information may influence the selection of GAS serotypes used in vaccine development.