Streptococci from children in Nepal share genetic relatedness with isolates from other countries
|
|
Genetically diverse group A streptococci from children in far western Nepal share high genetic relatedness with isolates from other countries.
According to a study from the United States, “The genetic diversity of group A streptococci (GAS) throughout much of the world has not been adequately explored.”
“To assess genetic variation among GAS in western Nepal, 120 noninvasive GAS, collected from eight different villages, were genetically characterized using emm typing, sof sequencing, and multilocus sequence typing (MLST). A high level of genetic diversity was observed among these isolates, with 51 genotypes based upon 51 multilocus sequence types (STs), 45 emm sequence types, and 28 sof sequence types,” said Varja Sakota and colleagues at the U.S. Centers for Disease Control and Prevention.
“On the basis of shared ST-emm and sof-emm associations, 40 of the 51 genotypes were identical or highly related to genotypes characterized from locations outside of Nepal, even though most of the emm sequence and clonal types are rare among GAS within the United States,” the researchers reported. “When analyzing all known STs highly related to Nepal STs, only one example of similar STs shared between a sof PCR-positive strain and a sof PCR-negative strain was observed.”
“Since previous data indicate free exchange of MLST loci between sof-positive and sof-negative strains, there is possibly selection against the expansion of subclones resulting from horizontal transfers of sof or emm genes between sof-positive and sof-negative strains,” noted the scientists. “All 45 emm types encountered in Nepal have also been documented from other countries.”
“These data, together with data encompassing the past decade of emm type surveillance, support the possibility that most existing GAS emm types have been discovered,” they concluded. “Similarly, since most (40/51) strain types were highly related to strains found elsewhere, it is likely that a major fraction of the existing GAS clonal complexes have been discovered.”
Sakota and associates published the results of their research in the Journal of Clinical Microbiology (Genetically diverse group A streptococci from children in Far-Western Nepal share high genetic relatedness with isolates from other countries. J Clin Microbiol, 2006;44(6):2160-2166).
For additional information, contact Bernard Beall, Division of Bacterial and Mycotic Diseases, Respiratory Diseases Branch, Centers for Disease Control and Prevention, Mailstop C02, 1600 Clifton Road NE, Atlanta, GA 30333, USA. E-mail: .(JavaScript must be enabled to view this email address).
The publisher of the Journal of Clinical Microbiology can be contacted at: American Society for Microbiology, 1752 N Street NW, Washington, DC 20036-2904, USA.
Print Version
Tell-a-Friend comments powered by Disqus
