A comparison of group A streptococci from invasive and uncomplicated infections: are virulent clones responsible for serious streptococcal infections?
From the mid-1980s, numerous reports of invasive group A streptococcal infections suggested that "highly virulent clones" were responsible. However, there have been virtually no extensive reports and comparisons of diverse temporal and geographic community isolates from uncomplicated throat infections to confirm the hypothesis. A unique collection of such "control" strains allowed in-depth assessment of association of M serotypes 1, 3, and 28 "clones" with invasive infections. Clones were defined by using small-fragment chromosomal restriction-enzyme analysis, pulsed-field gel electrophoresis, and M protein gene (emm) sequencing. After comparison with controls, no clone within these M serotypes had statistically increased association with invasive infections. The prevalence of specific virulence-associated clones appeared to essentially reflect their normal population prevalence. Although this does exclude other potential streptococcal factors, these findings suggest that host factors including individual and population-based immunity must also be significant in influencing infection potential.
Johnson
Dwight R
DR
Department of Pediatrics, World Health Organization Collaborating Center for Reference and Research on Streptococci, University of Minnesota Medical School, 420 Delaware Street SE, Minneapolis, MN 55455, USA. johns154@umn.edu
Wotton
Jason T
JT
Shet
Anita
A
Kaplan
Edward L
EL
D000595:Amino Acid Sequence; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis*; D016521:Electrophoresis, Gel, Pulsed-Field; D016680:Genome, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D012703:Serotyping; D013290:Streptococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D013297:Streptococcus pyogenes / Q000145:classification* / Q000235:genetics / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; C014689:streptococcal M protein