|Year : 2001 | Volume
| Issue : 3 | Page : 161--162
EMM types of streptococcus pyogenes in Chennai
T Menon1, AM Whatmore2, S Srivani1, MP Kumar1, N Anbumani1, S Rajaji3,
1 Department of Microbiology, Dr ALM PGIBMS, University of Madras, Chennai, India
2 University of Warwick, Coventry, United_Kingdom
3 The Childs Trust Hospital, Chennai, India
Department of Microbiology, Dr ALM PGIBMS, University of Madras, Chennai
The M protein of group A Streptococcus (GAS) is the major virulence factor and is coded by the emm gene. The current serologic M typing methods are now being replaced by alternate means of M type deduction such as emm gene sequencing. This is the first report of emm types of GAS which are prevalent in south India. We found no marked preponderance of any single emm sequence among our clinical isolates with 11 emm sequences being present in 34 isolates.
|How to cite this article:|
Menon T, Whatmore A M, Srivani S, Kumar M P, Anbumani N, Rajaji S. EMM types of streptococcus pyogenes in Chennai.Indian J Med Microbiol 2001;19:161-162
|How to cite this URL:|
Menon T, Whatmore A M, Srivani S, Kumar M P, Anbumani N, Rajaji S. EMM types of streptococcus pyogenes in Chennai. Indian J Med Microbiol [serial online] 2001 [cited 2020 Aug 8 ];19:161-162
Available from: http://www.ijmm.org/text.asp?2001/19/3/161/8156
Epidemiology of GAS infections is usually studied by using serological tests for M and T protein antigens. Serotyping has been the traditional method of characterization of GAS isolates. It is based on the variation in the surface exposed amino termini of M protein, which has identified more than 100 M types, each of which is often associated with specific T antigen patterns. However M typing reagents are not widely available and difficult to prepare, many strains are non-typable with the available stock of M typing sera, and hence alternate methods of typing GAS have been sought.
The Vir locus of the chromosome of GAS has a cluster of emm like gene which includes the mrp, emm and enn gene groups. The emm gene encodes the M protein of GAS. The variable 5' sequence of the emm genes confers distinguishable M serotypes to GAS. Sequencing emm specific PCR products is presently used for routine typing of GAS. The present study reports the prevalence of emm types in patients and carriers in Chennai, south India.
Materials and Methods
34 clinical isolates of GAS from different sources (throat swab, urine, blood, pus) and 9 isolates from normal school children aged 5-15 years, were included in the study. The strains were serogrouped using co-agglutination reagent procured from Christian Medical College, Vellore and by Streptex Kit (Abbott Murex). Strains confirmed as GAS were typed by emm gene sequencing. Sequences between 170bp and 400bp corresponding to the 5' variable region of emm were determined as described previously  and the emm type designated by interrogation of the CDC emm sequence database (http://www.cdc.gov/ncidod/biotech strepblast.html). Sequences showing> 95% nucleotide identity to emm sequences already present in the database were designated as belonging to these emm types.
11 emm gene types were identified among the 34 clinical isolates of GAS and 3 emm gene types were identified among 9 carrier stains [Table].
Clinical strains thus appeared to belong to a heterogeneous group of emm types. The most commonly encountered emm type in isolates from patients with pharyngitis was emm 92 which was seen in 6/21 cases (28.6%) which was seen in 5/21 cases (23.8%).
It is of interest that of the six emm types more commonly seen in the US (emm 1, emm 3, emm, 28, emm, 12, emm 4, and emm 11) only emm 12 was seen in this population. This observation would be of great significance in designing a vaccine based on emm sequences, and would imply that a vaccine designed for a Western population may not be suitable for India.
The sample size of this study is small, nevertheless, it is first report of emm types of GAS present in south India. Emm typing is a useful method of monitoring the spread and genetic variability of GAS in geographically diverse locations.
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