Abstract
BackgroundGroup 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 emm types of GAS in India has been described, there is a lack of data describing either the comparative distribution of emm 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 emm type pattern of Group A streptococcus throat and skin isolates from India. Additionally, the association of these isolates with closely related sic (crs), a multifunctional compliment binding virulence factor, was also explored.ResultsOf the 94 (46 throat and 48 skin) isolates analyzed, 37 emm types were identified. The most frequently observed emm types were emm49 (8.5%) and emm112 (7.5%) followed by 6.5% each of emm1-2, emm75, emm77, and emm81. Out of 37 emm types, 27 have been previously reported and rest were isolated for the first time in the Indian Community. The predominant emm types of throat (emm49 and emm75) samples were different from those of skin (emm44, emm81 and emm112) samples. After screening all the 94 isolates, the crs gene was found in six emm1-2 (crs1-2) isolates, which was confirmed by DNA sequencing and expression analysis. Despite the polymorphic nature of crs, no intravariation was observed within crs1-2. However, insertions and deletions of highly variable sizes were noticed in comparison to CRS isolated from other emm types (emm1.0, emm57). CRS1-2 showed maximum homology with CRS57, but the genomic location of crs1-2 was found to be the same as that of sic1.0. Further, among crs positive isolates, speA was only present in skin samples thus suggesting possible role of speA in tissue tropism.ConclusionDespite the diversity in emm type pattern of throat and skin isolates, no significant association between emm type and source of isolation was observed. The finding that the crs gene is highly conserved even in two different variants of emm1-2 GAS (speA +ve and -ve) suggests a single allele of crs may be prevalent in the highly diverse throat and skin isolates of GAS in India.
Highlights
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
This study showed the conserved nature of the crs1-2 gene among Indian isolates, unlike drs, crs1-2 was found to be highly polymorphic when compared to isolates from other countries
Characterization of GAS strains by emm typing For the first time, the emm type distribution of both throat and skin isolates of Group A streptococcus from India was studied and compared. 94 isolates associated with either throat or skin were categorized into 37 different emm types (Table 1)
Summary
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. Distribution of emm types of GAS in India has been described, there is a lack of data describing either the comparative distribution of emm types in throat versus skin isolates, or the distribution of certain virulence factors amongst these isolates. In the present study we have monitored the emm type pattern of Group A streptococcus throat and skin isolates from India. We have explored for the first time the presence of the crs gene in emm isolates of Group A streptococcus from throat and skin infections. This study showed the conserved nature of the crs gene among Indian isolates, unlike drs, crs was found to be highly polymorphic when compared to isolates from other countries
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