Geographic and Temporal Distribution and Molecular Characterization of Two Highly Pathogenic Clones ofStreptococcus pyogenesExpressing Allelic Variants of Pyrogenic Exotoxin A (Scarlet Fever Toxin)

Abstract

The molecular population genetics and pathogenic potential of North American and European invasive strains of Streptococcus pyogenes were assessed. Isolates from recent invasive infections and from infections in the 1920s and 1930s were characterized for multilocus enzyme genotype and allelic variation in the gene (speA) that encodes streptococcal pyrogenic exotoxin (SPE) A (scarlet fever toxin). A subset of strains was studied for allelic variation in genes that encode SPE B and streptokinase. All contemporary strains assigned to electrophoretic types (ETs) 1 and 2 that synthesize SPE A have the speA2 and speA3 allelic variants, respectively, and their relative virulence in two mouse models is similar to that of strains of the same ET and M protein types recovered earlier. In contrast, ET 1 and 2 isolates from disease episodes in the 1920s and 1930s contain the speA1 allele. The data suggest there may be temporal and geographic variation in the occurrence of clone--virulence factor allele combinations, an observation that may in part explain fluctuations in disease frequency, severity, and character.

Clonal diversity ofStreptococcus pyogeneswithin some M-types revealed by multilocus enzyme electrophoresis

“…Strains typed as ET 1 and 9, are closely related (12 % allozyme differences) to Petal 49 (ET 8), a classical isolate causing APSGN. This pattern is in agreement with data demonstrating that TSLS outbreaks are usually caused by two or three distinct clones [25] rather than by a single clone as in the case of meningitis [26]. Further support comes from the results of pulsed field electrophoresis and DNA fingerprinting studies which showed different RFLP patterns for streptococci of the same M-type.…”

Inactivation of Streptococcus pyogenes extracellular cysteine protease significantly decreases mouse lethality of serotype M3 and M49 strains.

“…AM3 and CS101 have allele speB3 and speB65 , respectively. Allele speB3 occurs in M3 strains commonly recovered from patients with invasive streptococcal disease and has been described previously (8,29; GenBank accession number L26126). Allele speB65 , which has not been described previously, differs from a reference speB sequence deposited in GenBank (accession number M35110) by the occurrence of five nucleotide changes that would result in two amino acid substitutions (Ala111Val and Ala317Ser) in the 40-kD extracellular zymogen.…”

Clonal structure of invasiveStreptococcus pyogenesin Northern Scotland

“…The close correlation between DNA restriction fragment profile and serotype [131 suggests that these strains may belong to the ET1 /ET2/I clone or group of clones, a conclusion strengthened by the work of Musser and colleagues [14].…”