Streptococcus invasive locus (sil) in Group A Streptococcus causing non-invasive infections in Chennai, South India
© Bajoria and Menon; licensee BioMed Central Ltd. 2012
Published: 4 May 2012
Group A Streptococcus (GAS) causes diseases ranging from superficial skin & throat infections to severe life-threatening diseases. Streptococcus invasive locus (sil) is a virulence gene responsible for pathogenesis of GAS. This study intends to detect the presence of sil gene among the non-invasive GAS and its association with toxin genes, erythromycin resistance genes, and emm types.
A total of 85 GAS isolates (43 pyoderma, 18 pharyngotonsilitis, 24 carrier) were screened for presence of sil C&D gene, toxin genes (speA, speB, speC, speG, smeZ, speH, speJ, ssa, speF), and erm genes by PCR. emm typing was done by emm gene amplification and sequencing.
Among 85 isolates, 20/85 (23.5%) were positive for sil C and 27/85 (31.8%) isolates were positive for sil D. Both sil C&D were present in 20/85 (23.5%) isolates, whereas 58/85 (68.2%) isolates were negative for both sil C&D. Comparing the presence of sil C&D among the isolates from different sources, no significant difference (p>0.05) was found. There was no significant differences between the toxin gene profile and presence of erm genes between sil-positive/negative isolates (p>0.05). Thirty nine different emm types were observed among the 85 GAS, reflecting a diversity of 45.88%. emm types harbouring sil were emm89.0b(5), emm82.1(3), emm74.0(2), emm80.0(1), emm95.0(1), emm105.0(1), emm11.0(1), emm44.0(1), emm55.0(1), emm66.0(1), st2460.1(1), st6735.0(1), stG652.0(1). Many of these emm types were also found among the sil-negative strains.
23.5% of the non-invasive GAS harboured sil. There was no specific association of sil genes with toxin genes erm genes, emm types or source of isolation.
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