Distribution of small native plasmids in Streptococcus pyogenes in India.

Abstract Complete characterization of a Streptococcus pyogenes population from a defined geographic region comprises information on the plasmids that circulate in these bacteria. Therefore, we determined the distribution of small plasmids ( S. pyogenes isolates from India, where diversity of strains and incidence rates of S. pyogenes infections are high. The collection comprised 77 emm -types. For plasmid detection and discrimination, we developed PCRs for different plasmid replication initiation protein genes, the putative repressor gene cop G and bacteriocin genes dys A and scn M57. Plasmid distribution was limited to 13 emm -types. Co-detection analysis using aforementioned PCRs revealed four distinct plasmid sub-types, two of which were previously unknown. Representative plasmids pA852 and pA996 of the two uncharacterized plasmid sub-types were sequenced. These two plasmids could be assigned to the pMV158 and the pC194/pUB110 family of rolling-circle plasmids, respectively. The majority of small plasmids found in India belonged to the two newly characterized sub-types, with pA852- and pA996-like plasmids amounting to 42% and 22% of all detected plasmids, respectively. None of the detected plasmids coded for a known antibiotic resistance gene. Instead, all of the four plasmid sub-types carried known or potential bacteriocin genes. These genes may have influence on the evolutionary success of certain S. pyogenes genotypes. Notably, pA852-like plasmids were found in all isolates of the most prevalent emm -type 11.0. Together, a priori fitness of this genotype and increased fitness due to the acquired plasmids may have rendered type emm 11.0 successful and caused the prevalence of pA852-like plasmids in India.