Superantigen profiles of <it>emm </it>and <it>emm</it>-like typeable and nontypeable pharyngeal streptococcal isolates of South India

• Main Authors: Anand Thangarajan (Author), Rajesh Thangamani (Author), Rajendhran Jeyaprakash (Author), Gunasekaran Paramasamy (Author)
• Format: Book
• Published: BMC, 2012-02-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.

Summary

<p>Abstract</p> <p>Background</p> <p>The major virulence factors determining the pathogenicity of streptococcal strains include M protein encoded by <it>emm </it>and <it>emm</it>-like (<it>emmL</it>) genes and superantigens. In this study, the distribution of <it>emm, emmL </it>and superantigen genes was analyzed among the streptococcal strains isolated from the patients of acute pharyngitis.</p> <p>Methods</p> <p>The streptococcal strains were isolated from the throat swabs of 1040 patients of acute pharyngitis. The <it>emm </it>and <it>emmL </it>genes were PCR amplified from each strain and sequenced to determine the <it>emm </it>types. The dot-blot hybridization was performed to confirm the pathogens as true <it>emm </it>nontypeable strains. The presence of eleven currently known superantigens was determined in all the strains by multiplex PCR.</p> <p>Results</p> <p>Totally, 124 beta-hemolytic streptococcal strains were isolated and they were classified as group A streptococcus (GAS) [15.3% (19/124)], group C streptococcus (GCS) [59.7% (74/124)] and group G streptococcus (GGS) [25.0% (31/124)]. Among 124 strains, only 35 strains were <it>emm </it>typeable and the remaining 89 strains were <it>emm </it>nontypeable. All GAS isolates were typeable, whereas most of the GCS and GGS strains were nontypeable. These nontypeable strains belong to <it>S. anginosus </it>[75.3% (67/89)] and <it>S. dysgalactiae </it>subsp. <it>equisimilis </it>[24.7% (22/89)]. The <it>emm </it>and <it>emmL </it>types identified in this study include <it>emm12.0 </it>(28.6%), <it>stG643.0 </it>(28.6%), <it>stC46.0 </it>(17.0%), <it>emm30.11 </it>(8.5%), <it>emm3.0 </it>(2.9%), <it>emm48.0 </it>(5.7%), <it>st3343.0 </it>(2.9%), <it>emm107.0 </it>(2.9%) and <it>stS104.2 </it>(2.9%). Various superantigen profiles were observed in typeable as well as nontypeable strains.</p> <p>Conclusions</p> <p>Multiplex PCR analysis revealed the presence of superantigens in all the typeable strains irrespective of their <it>emm </it>types. However, the presence of superantigen genes in <it>emm </it>and <it>emmL </it>nontypeable strains has not been previously reported. In this study, presence of at least one or a combination of superantigen coding genes was identified in all the <it>emm </it>and <it>emmL </it>nontypeable strains. Thus, the superantigens may inevitably play an important role in the pathogenesis of these nontypeable strains in the absence of the primary virulence factor, M protein.</p>

Item Description

10.1186/1476-0711-11-3
1476-0711