Comparative analysis of emm type pattern of Group A Streptococcus throat and skin isolates from India and their association with closely related SIC, a streptococcal virulence factor

Abstract

<p>Abstract</p> <p>Background</p> <p>Group A streptococcus (GAS) causes a wide variety of life threatening diseases in humans and the incidence of such infections is high in developing countries like India. Although distribution of <it>emm </it>types of GAS in India has been described, there is a lack of data describing either the comparative distribution of <it>emm </it>types in throat versus skin isolates, or the distribution of certain virulence factors amongst these isolates. Therefore in the present study we have monitored the <it>emm </it>type pattern of Group A streptococcus throat and skin isolates from India. Additionally, the association of these isolates with closely related <it>sic </it>(<it>crs</it>), a multifunctional compliment binding virulence factor, was also explored.</p> <p>Results</p> <p>Of the 94 (46 throat and 48 skin) isolates analyzed, 37 <it>emm </it>types were identified. The most frequently observed <it>emm </it>types were <it>emm</it>49 (8.5%) and <it>emm</it>112 (7.5%) followed by 6.5% each of <it>emm</it>1-2, <it>emm</it>75, <it>emm</it>77, and <it>emm</it>81. Out of 37 <it>emm </it>types, 27 have been previously reported and rest were isolated for the first time in the Indian Community. The predominant <it>emm </it>types of throat (<it>emm</it>49 and <it>emm</it>75) samples were different from those of skin (<it>emm</it>44, <it>emm</it>81 and <it>emm</it>112) samples. After screening all the 94 isolates, the <it>crs </it>gene was found in six <it>emm</it>1-2 (<it>crs</it>1-2) isolates, which was confirmed by DNA sequencing and expression analysis. Despite the polymorphic nature of <it>crs</it>, no intravariation was observed within <it>crs</it>1-2. However, insertions and deletions of highly variable sizes were noticed in comparison to CRS isolated from other <it>emm </it>types (<it>emm</it>1.0, <it>emm</it>57). CRS1-2 showed maximum homology with CRS57, but the genomic location of <it>crs</it>1-2 was found to be the same as that of <it>sic</it>1.0. Further, among <it>crs </it>positive isolates, <it>spe</it>A was only present in skin samples thus suggesting possible role of <it>spe</it>A in tissue tropism.</p> <p>Conclusion</p> <p>Despite the diversity in <it>emm </it>type pattern of throat and skin isolates, no significant association between <it>emm </it>type and source of isolation was observed. The finding that the <it>crs </it>gene is highly conserved even in two different variants of <it>emm</it>1-2 GAS (<it>spe</it>A +ve and -ve) suggests a single allele of <it>crs </it>may be prevalent in the highly diverse throat and skin isolates of GAS in India.</p