Downloaded from www.microbiologyresearch.org by IP: 54.70.40.11 On: Sun, 25 Nov 2018 08:28:20 International Journal of Systematic Bacteriology (1998), 48, 1 23 1-1 243 Printed in Great Britain Genetic relationships among the different phenotypes of Streptococcus dysgalactiae strains Verbnica V. Vieira,' Lucia M. Teixeira,' Viviane Zahner,' Hooman Momen,' Richard R. Fa~klam,~ Arnold G. Steiger~alt,~ Don J. Brenner3 and Angela C. D. Castrol Author for correspondence: Angela C. D. Castro. Tel: + 55 21 2604193. e-mail : immmadc@microbio.ufrj.br lnstituto de Microbiologia, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-590, Brazil * lnstituto Oswaldo Cruz, Rio de Janeiro 21045, Brazil Division of Bacterial and Mycotic Diseases, NCID, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA The species Streptococcus dysgalactiae was proposed to accommodate a heterogeneous group of streptococci associated with infections in animals and human beings. This taxon is now considered t o include animal isolates of a- haemolytic group C streptococci, previously called 5. dysgalactiae; animal and human isolates of P-haemolytic group C streptococci, previously called '5. equisimilis '; P-haemolytic group L strains associated with infections in animals and, rarely, in humans; and P-haemolytic group G strains isolated from humans. DNA-DNA reassociation experiments (hydroxyapatite method) and multilocus enzyme electrophoresis (MEE) were performed on reference strains and clinical isolates to determine the genetic relationships among these different phenotypic categories. DNA-DNA hybridization tests showed that they were related at the species level, despite the phenotypic and host heterogeneity. Both genotypic and phenotypic characterization indicated that 5. dysgalactiae could be separated into two major sub-groups. The first sub- group contained a-haemolytic strains that showed levels of DNA relatedness with the type strain of 5. dysgalactiae ranging from 84 to 90% and from 82 to 88% under optimal (55 "C) and stringent (70 "C) conditions, respectively. The second sub-group contained p-haemolytic strains showing levels of relatedness ranging from 71 to 79% (55 "C) and from 62 to 73% (70 "C). Percentage divergence varied from 0-5t o 1*0% (a-haemolytic group) and from 2.0 to 3*5% (P-haemolytic group). A dendrogram based on phenotypic similarity between the enzyme bands produced by MEE showed a Jaccard similarity coefficient of 045 between the subclusters formed by the two sub-groups. The results of phenotypic and genotypic characterization were consistent with a published proposal to divide 5, dysgalactiae into two subspecies, 5. dysgalactiae subsp. dysgalactiae and S. dysgalactiae subsp. equisimilis, with a few modifications. Keywords: Streptococcus dysgalactiae, multilocus enzyme electrophoresis, DNA-DNA hybridization, genetic relationships INTRODUCTION The classic Lancefield serological grouping has been of major importance in the classification and identi- fication of P-haemolytic streptococci (Lancefield, ....................... ..... .......... ........... ................. ..... ......................................................................... Abbreviations: ET, electrophoretic type; MEE, multilocus enzyme electro- phoresis; UPGMA, unweighted pair group method with arithmetic averages. 1933; Lancefield & Hare, 1935). However, in most cases, when DNA-DNA relatedness studies were applied to the P-haemolytic streptococci, no corre- lation between genetic relationships and streptococcal group antigens was observed (Kilpper-Balz & Schleifer, 1984). Streptococci belonging to Lancefield groups C and G are phenotypically and genotypically diverse. These streptococci can be initially characterized as forming either large or small colonies, which have been differen- ~- 00774 0 1998 IUMS 1231