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Journal of Clinical Microbiology, July 2009, p. 2046-2054, Vol. 47, No. 7
0095-1137/09/$08.00+0 doi:10.1128/JCM.00246-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Genetic Relationships Deduced from emm and Multilocus Sequence Typing of Invasive Streptococcus dysgalactiae subsp. equisimilis and S. canis Recovered from Isolates Collected in the United States 
Yusra Ahmad,1
Robert E. Gertz Jr.,1
Zhongya Li,1
Varja Sakota,1
Laura N. Broyles,2
Chris Van Beneden,1
Richard Facklam,1
P. Lynn Shewmaker,1
Arthur Reingold,4,5
Monica M. Farley,2,3 and
Bernard W. Beall1*
Respiratory Diseases Branch, Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia,1 Division of Infectious Diseases, Emory University School of Medicine, Atlanta, Georgia,2 Atlanta Veterans Affairs Medical Center, Atlanta, Georgia,3 California Emerging Infections Program, Oakland, California,4 University of California at Berkeley School of Public Health, Berkeley, California5
Received 4 February 2009/ Accepted 16 April 2009
Beta-hemolytic group C and G streptococci cause a considerable invasive disease burden and sometimes cause disease outbreaks. Little is known about the critical epidemiologic parameter of genetic relatedness between isolates. We determined the emm types of 334 Streptococcus dysgalactiae subsp. equisimilis isolates, and attempted emm typing of 5 Streptococcus canis isolates from a recent population-based surveillance for invasive isolates. Thirty-four emm types were observed, including one from S. canis. We formulated multilocus sequence typing (MLST) primers with six of the seven loci corresponding to the Streptococcus pyogenes MLST scheme. We performed MLST with 65 of the 334 surveillance isolates (61 S. dysgalactiae subsp. equisimilis isolates, 4 S. canis isolates) to represent each emm type identified, including 2 to 3 isolates for each of the 25 redundantly represented emm types. Forty-one MLST sequence types (STs) were observed. Isolates within 16 redundantly represented S. dysgalactiae subsp. equisimilis emm types shared identical or nearly identical STs, demonstrating concordance between the emm type and genetic relatedness. However, seven STs were each represented by two to four different emm types, and 7 of the 10 S. dysgalactiae subsp. equisimilis eBURST groups represented up to six different emm types. Thus, S. dysgalactiae subsp. equisimilis isolates were similar to S. pyogenes isolates, in that strains of the same emm type were often highly related, but they differed from S. pyogenes, in that S. dysgalactiae subsp. equisimilis strains with identical or closely similar STs often exhibited multiple unrelated emm types. The phylogenetic relationships between S. dysgalactiae subsp. equisimilis and S. pyogenes alleles revealed a history of interspecies recombination, with either species often serving as genetic donors. The four S. canis isolates shared highly homologous alleles but were unrelated clones without evidence of past recombination with S. dysgalactiae subsp. equisimilis or S. pyogenes.
* Corresponding author. Mailing address: CDC Streptococcus Lab, 1600 Clifton Rd., NE, MS-C02, Atlanta, GA 30329. Phone: (404) 639-1237. Fax: (404) 639-4215. E-mail: beb0{at}cdc.gov
Published ahead of print on 22 April 2009.
Journal of Clinical Microbiology, July 2009, p. 2046-2054, Vol. 47, No. 7
0095-1137/09/$08.00+0 doi:10.1128/JCM.00246-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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