Molecular heterogeneity among north Indian isolates of Group A Streptococcus

Global Streptococcus pyogenes strain diversity, disease associations, and implications for vaccine development: a systematic review

The high strain diversity of Streptococcus pyogenes serves as a major obstacle to vaccine development against this leading global pathogen. We did a systematic review of studies in PubMed, MEDLINE, and Embase that reported the global distribution of S pyogenes emm-types and emm-clusters from Jan 1, 1990, to Feb 23, 2023. 212 datasets were included from 55 countries, encompassing 74 468 bacterial isolates belonging to 211 emm-types. Globally, an inverse correlation was observed between strain diversity and the UNDP Human Development Index (HDI; r=-0·72; p<0·0001), which remained consistent upon subanalysis by global region and site of infection. Greater strain diversity was associated with a lower HDI, suggesting the role of social determinants in diseases caused by S pyogenes. We used a population-weighted analysis to adjust for the disproportionate number of epidemiological studies from high-income countries and identified 15 key representative isolates as vaccine targets. Strong strain type associations were observed between the site of infection (invasive, skin, and throat) and several streptococcal lineages. In conclusion, the development of a truly global vaccine to reduce the immense burden of diseases caused by S pyogenes should consider the multidimensional diversity of the pathogen, including its social and environmental context, and not merely its geographical distribution.

Echocardiographic Parameters, Clinical Profile and Presence of Streptococcus pyogenes Virulent Genes in Pharyngitis and Rheumatic Fever

Streptococcus pyogenes is a gram positive pathogen causing pharyngitis, mild infections to chronic complications (Rheumatic Heart Disease, RHD). In this study, echocardiographic and clinical profile in pharyngitis, rheumatic fever patients were compared with virulent genes emm, spe A, spe B and sof. Nearly 107 subjects were classified into Group I – Pharyngitis (n=30), Group II – Rheumatic Fever (n=30) and Group III – healthy controls (n=47). The isolated S.pyogenes from Group I and Group II patient’s throat swab were subjected to 16S rRNA gene sequence. Multiplex PCR was done for identification of virulent genes. Electrocardiogram and Echocardiography was done for all the groups. For statistical analysis ANOVA and t-test were used. Comparison between groups were done by Tukey’s Multiple Comparison test. Among 107 isolates, 16.7% emm gene were detected in Group I and 23.3% in Group II, 56.67 % of spe B in Group I and 73.33 % in Group II, 36.67% of sof gene in Group I and 40% in Group II. Mitral Regurgitation was most commonly encountered in rheumatic fever. Hemoglobin (<0.001) and RDW (<0.001) was significantly lower in Rheumatic Fever whereas Platelet count (<0.001) and Neutrophil (<0.001) was significantly higher when compared with control subjects by Tukey’s Multiple Comparison test. When we compared the genetic relationship with the Echocardiographic findings, presence of one, two or three genes showed moderate to severe regurgitation in Rheumatic Fever subjects.

Whole-Genome Sequence of an Indian Group A Streptococcus emm Type 1-2 Strain Isolated from a Blood Sample in North India

Group A Streptococcus emm type 1-2 is more prevalent than emm type 1 in India. Only partial information is available about the genetic characteristics of this type. Here, genome sequencing of emm type 1-2 strain 1085 (from blood) was conducted. A contig 2,010,300 bp long, with a total of 1,877 annotated proteins, was obtained (NCBI accession number CP047120, assembly accession number ASM983284v1).

Decoding the molecular epidemiology of group A streptococcus - an Indian perspective

PURPOSE

Unlike western countries the knowledge of group A streptococcus (GAS) epidemiology in India remains patchy and incomplete. Typing is crucial for surveillance as well as in predicting the efficacy of multivalent M protein vaccine. The present study aimed to explore the emm types of 206 invasive and non-invasive GAS isolates from South India as well as reviewing all the published literature on GAS molecular epidemiology from India thereby generating a pan-Indian data to predict the conjectural coverage of the 30-valent M-protein vaccine in this population.

METHODOLOGY

emm typing and superantigen (SAg) profiling of GAS along with reviewing literatures on GAS molecular epidemiology from India.

RESULTS

This study revealed a high diversity of emm types with emm 63, 82, 183, 85, 92, 169, 42, 44, 106, 74, 12 being frequently encountered, belonging to twenty emm clusters. The pan-Indian data on prevalent emm types further supports our study findings with 135 emm different types. Six clusters dominated accounting for 80 % of the GAS isolates: E3(26 %), E6(20 %), E2(11 %), E4(10 %), D4(7 %), E1(6 %). No significant association was noted between emm types and the nature of infection (P≥0.05) while a few SAg profiles were significantly associated with certain emm types. Pan Indian data revealed that only 16 % of the emm types encountered were included in proposed 30-valent M protein based vaccine.

CONCLUSION

The coverage among the South Indian GAS isolates was 28.2 % which increased to only 46.6 % with the cross-opsonic effect, thus highlighting the importance of developing a specific multivalent vaccine including the prevalent emm types in India or considering the use of conserved C-repeat vaccines and non-M protein based vaccines.

Molecular characterization and evaluation of the emerging antibiotic-resistant Streptococcus pyogenes from eastern India

Background

Group A Streptococcus strains causing wide variety of diseases, recently became noticeable in eastern India, are not amenable to standard treatment protocol thus enhancing the possibility of disease morbidity by becoming antibiotic resistance.

Methods

The association of Lancefield group A Streptococcal variation with degree of vir architectural diversity was evaluated using emm typing and restriction fragment length polymorphism analyses. The antibiotic sensitivity patterns were examined by modified Kirby-Bauer method of disk diffusion. Percentage calculations, 95% confidence interval and one-way ANOVA were used to assess differences in proportions.

Results

Our observations revealed 20 different emm types and 13 different HaeIII vir typing patterns. A 1.2 kb fragment was found in all HaeIII typing pattern. Fragments of 1.2 kb and 550 bp were conserved in majority of the isolates. HinfI digestion was found proficient in differentiating the strains of same vir typing patterns. Strong predominance of speC (85%) and speF (80%) genes have been observed encoding exotoxins production. 4 isolates were found to be erythromycin resistant and were of genotype emm49. High degree of tetracycline resistance was shown by 53.57% isolates which belonged to 12 different emm genotypes.

Conclusions

These findings suggested that in addition to emm typing, sequential application of HaeIII and HinfI restriction enzymes in vir typing analysis is an effective tool for group A streptococcal molecular characterization associated with antibiotic resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-2079-9) contains supplementary material, which is available to authorized users.

Whole genome sequencing reveals extensive community-level transmission of group A Streptococcus in remote communities

Impetigo is common in remote Indigenous children of northern Australia, with the primary driver in this context being Streptococcus pyogenes [or group A Streptococcus (GAS)]. To reduce the high burden of impetigo, the transmission dynamics of GAS must be more clearly elucidated. We performed whole genome sequencing on 31 GAS isolates collected in a single community from children in 11 households with ⩾2 GAS-infected children. We aimed to determine whether transmission was occurring principally within households or across the community. The 31 isolates were represented by nine multilocus sequence types and isolates within each sequence type differed from one another by only 0-3 single nucleotide polymorphisms. There was evidence of extensive transmission both within households and across the community. Our findings suggest that strategies to reduce the burden of impetigo in this setting will need to extend beyond individual households, and incorporate multi-faceted, community-wide approaches.

Molecular epidemiology and genomics of group A Streptococcus

Streptococcus pyogenes (group A Streptococcus; GAS) is a strict human pathogen with a very high prevalence worldwide. This review highlights the genetic organization of the species and the important ecological considerations that impact its evolution. Recent advances are presented on the topics of molecular epidemiology, population biology, molecular basis for genetic change, genome structure and genetic flux, phylogenomics and closely related streptococcal species, and the long- and short-term evolution of GAS. The application of whole genome sequence data to addressing key biological questions is discussed.

Immune response against M protein-conserved region peptides from prevalent group A Streptococcus in a North Indian population

BACKGROUND

Group A streptococci (GAS) cause infections with a high prevalence in most developing countries. A GAS vaccine under trial that is based on the amino-terminus of the M protein provides type-specific immunity, and hence seems ineffective in India because of heterogeneous emm types. However, the conserved C-terminal region of the M protein protects against multiple serotypes. In this paper, the immune response generated against the conserved C-repeat region of the M protein was checked in an Indian population to establish their vaccine candidature.

METHODS

When screened for GAS, patients with pharyngitis, rheumatic fever/rheumatic heart disease (RF/RHD), and invasive disease showed heterogeneous emm types, out of which five prevalent types (1-2, 11, 49, 75 and 112) were selected for the study. The C-terminal region of their M proteins showed conserved C1-, C2-, and C3-repeats. The C1-repeat was more diverse and had two different J14-like sequences. Peptides to these C-terminal regions (J14.1 and J14-R6) were designed. Antibodies against these peptides were analyzed using the sera of 130 GAS-infected volunteers.

RESULTS

Serum antibodies were significantly higher in patients with acute rheumatic fever, RHD, and invasive disease than in patients with pharyngitis or the healthy controls. The serum antibodies to these peptides was higher in teenagers and adults than in children.

CONCLUSION

Results showed an association between streptococcal disease progression and the age-related development of immunity to the conserved regions. Hence, these peptides could be considered protective in impeding streptococcal infections worldwide.

Differences in virulence repertoire and cell invasive potential of group A Streptococcus emm1-2 in comparison to emm1 genotype

Group A streptococcus (GAS, Streptococcus pyogenes) type emm1 is widely associated with streptococcal invasive disease. This type is prevalent worldwide but is rare in India. Instead, emm1-2 type which is closely related to emm1 but is a distinct type is more prevalent. Although emm1 has been well characterized, information available on emm1-2 is rare. In this study we present a comparative study of both types. DNA microarray analysis showed segregation of emm1 and emm1-2 isolates into two distinct clusters. Out of 229 arrayed genes, 83-87% were present, 6-9% absent and 4-8% genes were ambiguous in emm1 isolates. emm1-2 strains harboured only 68-77%, 11-13% were absent and 10-20% ambiguous genes. Fourteen genes, present in all emm1, were completely absent in the emm1-2 isolates. sfb1 is a gene which encodes for Streptococcal fibronectin binding adhesin and invasin which has restricted distribution among different emm types of GAS. A variant of sfb1 (sfb1-2) was the only gene which was present in all emm1-2 isolates, but absent from all emm1 strains. Sfb1 and Sfb1-2 differ in sequences in the aromatic domain and the proline rich repeat region, whereas the fibronectin binding region was conserved and exhibited similar fibronectin binding activity. The presence of Sfb1-2 in emm1-2 strains was concomitant with significantly higher fibronectin-binding and invasion efficiency of HEp-2 cells when compared to emm1 isolates. The role of Sfb1-2 in invasion was confirmed by latex bead assay. emm1-2 isolates follow membrane ruffling mechanism during invasion and intracellularly follow classical endocytic pathway. Further studies are required to understand the correlation between the presence of emm1-2 isolates and the disease pattern in North India.

Outbreak of Streptococcus pyogenes emm type 58 in a high dependency unit of a level-1 trauma center of India

Background and Aims:

Group A Streptococcus (GAS) can cause illnesses ranging from self-limited to severe, life-threatening, invasive infections. The objective of the following study was to investigate a suspected Streptococcus pyogenes outbreak in a high dependency unit (HDU) of our trauma center.

Materials and Methods:

All the isolates of beta hemolytic Streptococci were identified by standard microbiological methods, Vitek 2 system and latex agglutination tests. Antimicrobial susceptibility testing was performed as recommended by Clinical Laboratory Standards Institute. Exotoxin genes, including speA, speB, speC, speF, smeZ, ssa, speG, speH, speJ, speL, speM and speI were detected by polymerase chain reaction (PCR). The emm types of isolates of S. pyogenes were determined by sequencing the variable 5’ end of emm gene after amplification by PCR.

Results:

In a 28 bedded poly-trauma ward with a four bedded HDU three out of four patients developed S. pyogenes emm type 58 infection. The strain was macrolide and tetracycline resistant and produced the Streptococcal pyrogenic exotoxins speB, speC, speG, speF and smeZ. Surveillance sampling was done for investigation from patients, health-care workers and environmental samples.

Conclusion:

An outbreak of GAS infections was established caused by the uncommonly reported emm type 58. The outbreak was controlled by prompt treatment, intensive surveillance, feedback and training.

Seroprevalence of Streptococcal Inhibitor of Complement (SIC) suggests association of streptococcal infection with chronic kidney disease

BACKGROUND

Group A streptococcus (GAS) is an etiological agent for the immune mediated sequela post streptococcal glomerulonephritis (PSGN). In some populations PSGN is recognized as a risk factor for chronic kidney disease (CKD) and end-stage renal disease (ESRD). It was found that a significantly greater proportion of subjects with past history of PSGN than without the history exhibited seroreactions to streptococcal antigens called streptococcal inhibitor of complement (SIC) and to distantly related SIC (DRS). These antigens are expressed by major PSGN-associated GAS types. We therefore predicted that in populations such as India, which is endemic for streptococcal diseases and which has high prevalence of CKD and ESRD, greater proportions of CKD and ESRD patients exhibit seroreaction to SIC and DRS than healthy controls.

METHODS

To test this we conducted a SIC and DRS seroprevalence study in subjects from Mumbai area. We recruited 100 CKD, 70 ESRD and 70 healthy individuals.

RESULTS

Nineteen and 35.7% of CKD and ESRD subjects respectively were SIC antibody-positive, whereas only 7% of healthy cohort was seropositive to SIC. Furthermore, significantly greater proportion of the ESRD patients than the CKD patients is seropositive to SIC (p=0.02; odds ratio 2.37). No association was found between the renal diseases and DRS-antibody-positivity.

CONCLUSIONS

Past infection with SIC-positive GAS is a risk factor for CKD and ESRD in Mumbai population. Furthermore, SIC seropositivity is predictive of poor prognosis of CKD patients.

Rheumatic heart disease: progress and challenges in India

Rheumatic heart disease, a neglected disease, continues to be a burden in India and other developing countries. It is a result of an autoimmune sequalae in response to group A beta hemolytic streptococcus (GAS) infection of the pharynx. Acute rheumatic fever (RF), a multisystem inflammatory disease, is followed by rheumatic heart disease (RHD) and has manifestations of joints, skin and central nervous system involvement. A review of epidemiological studies indicates unchanged GAS pharyngitis and carrier rates in India. The apparent decline in RHD rates in India as indicated by the epidemiological studies has to be taken with caution as methodological differences exist among studies. Use of echocardiography increases case detection rates of RHD in population surveys. However, the significance of echo based diagnosis of carditis needs further evaluation to establish the significance. Research in this area through prospective follow up studies will have to be undertaken by the developing countries as the interest of developed countries in the disease has waned due the declined burden in their populations. Prevention of RHD is possible through treatment of GAS pharyngitis (primary prophylaxis) and continued antibiotic treatment for number of years in patients with history of RF to prevent recurrences (secondary prophylaxis). The cost effectiveness and practicality of secondary prophylaxis is well documented. The challenge to any secondary prophylaxis program for prevention of RF in India will be the availability of benzathine penicillin G and dissipation of fears of allergic reactions to penicillin among practitioners, general public and policy makers. The authors review here the progress and challenges in epidemiology, diagnosis and primary and secondary prevention of RF and RHD.

Variability in the distribution of genes encoding virulence factors and putative extracellular proteins of Streptococcus pyogenes in India, a region with high streptococcal disease burden, and implication for development of a regional multisubunit vaccine

Streptococcus pyogenes causes a wide variety of human diseases and is a significant cause of morbidity and mortality. Attempts to develop a vaccine were hampered by the genetic diversity of S. pyogenes across different regions of the world. This study sought to identify streptococcal antigens suitable for a region-specific vaccine in India. We used a two-step approach, first performing epidemiological analysis to identify the conserved antigens among Indian isolates. The second step consisted of validating the identified antigens by serological analysis. The 201 streptococcal clinical isolates from India used in this study represented 69 different emm types, with emm12 being the most prevalent. Virulence profiling of the North and South Indian S. pyogenes isolates with a custom-designed streptococcal virulence microarray identified seven conserved putative vaccine candidates. Collagen-like surface protein (SCI), putative secreted 5'-nucleotidase (PSNT), and C5a peptidase were found in 100% of the isolates, while R28, a putative surface antigen (PSA), and a hypothetical protein (HYP) were found in 90% of the isolates. A fibronectin binding protein, SfbI, was present in only 78% of the isolates. In order to validate the identified potential vaccine candidates, 185 serum samples obtained from patients with different clinical manifestations were tested for antibodies. Irrespective of clinical manifestations, serum samples showed high antibody titers to all proteins except for SCI and R28. Thus, the data indicate that PSNT, C5a peptidase, PSA, HYP, and SfbI are promising candidates for a region-specific streptococcal vaccine for the different parts of India.

Differences among group A streptococcus epidemiological landscapes: consequences for M protein-based vaccines?

Group A streptococcus (GAS) is a bacterial pathogen responsible for a wide array of disease pathologies in humans. GAS surface M protein plays multiple key roles in pathogenesis, and serves as a target for typing and vaccine development. In this review, we have compiled GAS epidemiological studies from several countries around the world to highlight the consequences on the theoretical efficacy of two different M protein-based vaccine strategies.

Disease burden due to Streptococcus dysgalactiae subsp. equisimilis (group G and C streptococcus) is higher than that due to Streptococcus pyogenes among Mumbai school children

Streptococcus pyogenes [group A streptococcus (GAS)], a human pathogen, and Streptococcus dysgalactiae subsp. equisimilis [human group G and C streptococcus (GGS/GCS)] are evolutionarily related, share the same tissue niche in humans, exchange genetic material, share up to half of their virulence-associated genes and cause a similar spectrum of diseases. Yet, GGS/GCS is often considered as a commensal bacterium and its role in streptococcal disease burden is under-recognized. While reports of the recovery of GGS/GCS from normally sterile sites are increasing, studies describing GGS/GCS throat colonization rates relative to GAS in the same population are very few. This study was carried out in India where the burden of streptococcal diseases, including rheumatic fever and rheumatic heart disease, is high. As part of a surveillance study, throat swabs were taken from 1504 children attending 7 municipal schools in Mumbai, India, during 2006-2008. GAS and GGS/GCS were identified on the basis of beta-haemolytic activity, carbohydrate group and PYR test, and were subsequently typed. The GGS/GCS carriage rate (166/1504, 11 %) was eightfold higher than the GAS carriage (22/1504, 1.5 %) rate in this population. The 166 GGS/GCS isolates collected represented 21 different emm types (molecular types), and the 22 GAS isolates represented 15 different emm types. Although the rate of pharyngitis associated with GGS/GCS is marginally lower than with GAS, high rates of throat colonization by GGS/GCS underscore its importance in the pathogenesis of pharyngitis.

School-based prevention of acute rheumatic fever: a group randomized trial in New Zealand

BACKGROUND

Acute rheumatic fever (ARF) and its sequela, rheumatic heart disease is the commonest cause of childhood cardiac morbidity globally. The current approach to the prevention of a primary attack of rheumatic fever in children using oral medication for streptococcal pharyngitis is poorly supported. The efficacy of injectable penicillin, in high rheumatic fever incidence military environments is indisputable.

OBJECTIVE

To evaluate school-based control of rheumatic fever in an endemic area.

METHODS

Fifty-three schools ( approximately 22,000 students) from a rheumatic fever high incidence setting ( approximately 60/100,000) in Auckland, New Zealand were randomized. The control group received routine general practice care. The intervention was a school-based sore throat clinic program with free nurse-observed oral penicillin treatment of group A streptococcal pharyngitis. The outcome measure was ARF in any child attending a study school. Analysis A defined ARF cases using criteria derived from Jones Criteria 1965 (definite) and 1956 (probable) with more precise definitions. Analysis B was based on 1992 Jones criteria but also included echocardiography to determine definite cases.

RESULTS

In Analysis A, 24 (55/100,000) cases occurred in clinic schools and 29 (67/100,000) in nonclinic schools, a 21% reduction when adjusted for demography and study design (P = 0.47). Analysis B revealed a 28% reduction 26 (59/100,000) and 33 (77/100,000) cases, respectively (P = 0.27).

CONCLUSION

This study involving 86,874 person-years showed a nonsignificant reduction in the school-based sore throat clinic programs.

emm and C-repeat region molecular typing of beta-hemolytic Streptococci in a tropical country: implications for vaccine development

We designed a study to investigate the molecular epidemiology of group A streptococcal (GAS) and group C and G streptococcal (GCS and GGS) disease in Fiji, a country which is known to have a high burden of streptococcal disease. Molecular typing of the N-terminal portion (emm typing) of the M protein was performed with 817 isolates (535 GAS and 282 GCS/GGS). We also performed genotyping of the C-repeat region in 769 of these isolates to identify J14 sequence types. The profile of emm types for Fiji was very different from that found for the United States and Europe. There were no dominant emm types and a large number of overlapping types among clinical disease states. Commonly found GAS emm types in industrialized countries, including emm1, emm12, and emm28, were not found among GAS isolates from Fiji. Over 93% of GAS isolates and over 99% of GCS/GGS isolates that underwent J14 sequence typing contained either J14.0 or J14.1. Our data have implications for GAS vaccine development in developing countries and suggest that a vaccine based upon the conserved region of the M protein may be a feasible option for Fiji and potentially for other tropical developing countries.

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

Background

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 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.

Results

Of 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.

Conclusion

Despite 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.

International quality assurance study for characterization of Streptococcus pyogenes

Surveillance of group A streptococcal (GAS) infections was undertaken as a major component of the European Commission-funded project on severe GAS disease in Europe (strep-EURO). One aim of strep-EURO was to improve the quality of GAS characterization by standardization of methods. An external quality assurance study (EQA) was therefore carried out to evaluate current global performance. Eleven strep-EURO and seven other streptococcal reference centers received a panel of 20 coded GAS isolates for typing. Conventional phenotypic typing (based on cell surface T and M protein antigens and opacity factor [OF] production) and molecular methods (emm gene typing) were used either as single or combined approaches to GAS typing. T typing was performed by 16 centers; 12 centers found one or more of the 20 strains nontypeable (typeability, 89%), and 11 centers reported at least one incorrect result (concordance, 93%). The 10 centers that tested for OF production achieved 96% concordance. Limited availability of antisera resulted in poor typeability values from the four centers that performed phenotypic M typing (41%), three of which also performed anti-OF typing (typeability, 63%); however, concordance was high for both M (100%) and anti-OF (94%) typing. In contrast, the 15 centers that performed emm gene sequencing achieved excellent typeability (97%) and concordance (98%), although comparison of the performance between centers yielded typeability rates from 65 to 100% and concordance values from 83 to 100%. With the rapid expansion and use of molecular genotypic methods to characterize GAS, continuation of EQA is essential in order to achieve international standardization and comparison of type distributions.

DRS is far less divergent than streptococcal inhibitor of complement of group A streptococcus

When 100 group A streptococcus isolates were screened, drs, a variant of sic, was identified in emm12 and emm55 isolates. Molecular characterization showed that the drs gene sequence is highly conserved, unlike the sic gene sequence. However, the variation in gene size observed was due to the presence of extra internal repeat sequences.