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. 2001 Apr;69(4):2416-27.
doi: 10.1128/IAI.69.4.2416-2427.2001.

Multilocus Sequence Typing of Streptococcus Pyogenes and the Relationships Between Emm Type and Clone

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Free PMC article

Multilocus Sequence Typing of Streptococcus Pyogenes and the Relationships Between Emm Type and Clone

M C Enright et al. Infect Immun. .
Free PMC article

Abstract

Multilocus sequence typing (MLST) is a tool that can be used to study the molecular epidemiology and population genetic structure of microorganisms. A MLST scheme was developed for Streptococcus pyogenes and the nucleotide sequences of internal fragments of seven selected housekeeping loci were obtained for 212 isolates. A total of 100 unique combinations of housekeeping alleles (allelic profiles) were identified. The MLST scheme was highly concordant with several other typing methods. The emm type, corresponding to a locus that is subject to host immune selection, was determined for each isolate; of the >150 distinct emm types identified to date, 78 are represented in this report. For a given emm type, the majority of isolates shared five or more of the seven housekeeping alleles. Stable associations between emm type and MLST were documented by comparing isolates obtained decades apart and/or from different continents. For the 33 emm types for which more than one isolate was examined, only five emm types were present on widely divergent backgrounds, differing at four or more of the housekeeping loci. The findings indicate that the majority of emm types examined define clones or clonal complexes. In addition, an MLST database is made accessible to investigators who seek to characterize other isolates of this species via the internet (http://www.mlst.net).

Figures

FIG. 1
FIG. 1
Dendrogram showing UPGMA cluster analysis of 212 GAS isolates. Bars to the left show allelic profiles (STs) represented by four or more isolates. Codes for strain designations at branch tips are listed in Table 2. Filled circles (n = 28) mark branches in which multiple descendants are all represented by a single emm type. Open circles (n = 3) mark branches containing isolates with different emm types but sharing identical allelic profiles.
FIG. 2
FIG. 2
Dendrogram of invasive isolates from the United States (1986 to 1999). UPGMA cluster analysis of all 84 isolates derived from normally sterile tissue sites, as listed in Table 2, is shown. The nomenclature at the branch tips indicate emm type, followed by the two-letter abbreviation of the state of origin and a unique isolate number (where necessary).

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