EMM typing of streptococcus group C and group G from Thai pateints by sequencing methods

Abstract

M protein is a major virulence factor that encode by emm gene, which were found in group A, C, and G Streptococci that can cause a several disease in human. In this study, we are interested in the variation of emm gene in GCS and GGS from Thai patients and also compared the sequences of emm gene between non-invasive and invasive isolates. Sixty GGS clinical isolates and 52 GCS clinical isolates obtained from patient admitted to King Chulalongkorn Memorial Hospital between 1995 to 2000 were included in this study. These isolates were divided into two group (non-invasive and invasive) by using the different site of infections. The emm gene was determined by the amplification and direct sequencing method according to Beall’s protocol. All of 60-emm gene from GGS isolates were amplified and sequenced. A variety of emm sequences (28 types, 47%) have been reported in this study including the identification of 6 (18%) emm variant types and 10 (26%) novel emm types demonstrating the diverse population of GGS isolates in Thailand. The common emm types of GGS isolates include STC6979 (7 isolates, 12%) and STC5345(6 isolates, 10%). As for GCS, only 24 out of 52-emm gene can be amplified and sequenced. Twelve (50%) different emm types including 7 (38%) novel emm types were identified in GCS. The most common emm types is ST245 (9 isolates, 42.8%). Interestingly, some emm types of GGS isolates were similar to GAS and GCS were similar to GGS databases suggesting the evidence of horizontal transfer of emm genes among GAS, GCS, and GGS. Different emm types seem to be associated with invasive compared to non-invasive group. However, these differences are not statistically significant. In conclusion, emm sequences types of GGS and GCS isolates in Thailand are diverse and unique. This information of the emm gene pattern from GCS and GGS in Thai patients will be useful in vaccine development to Streptococcus in Thailand.