Open AccessGenetic Diversity among Type emm28 Group A Streptococcus Strains Causing Invasive Infections and Pharyngitis
Author(s) -
Nicole M. Green,
Stephen B. Beres,
Edward A. Graviss,
James E. Allison,
Allison McGeer,
Jaana VuopioVarkila,
Rance B Lefebvre,
James M. Musser
Publication year - 2005
Publication title -
journal of clinical microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.349
H-Index - 255
eISSN - 1070-633X
pISSN - 0095-1137
DOI - 10.1128/jcm.43.8.4083-4091.2005
Subject(s) - prophage , biology , genetics , gene , virulence , genetic variation , genetic diversity , hypervariable region , amplicon , population , insertion sequence , streptococcus pyogenes , microbiology and biotechnology , genome , polymerase chain reaction , bacteriophage , escherichia coli , bacteria , transposable element , demography , sociology , staphylococcus aureus
Genome sequencing of group AStreptococcus (GAS) has revealed that prophages account for the vast majority of gene content differences between strains. Serotype M28 strains are a leading cause of pharyngitis and invasive infections, but little is known about genetic diversity present in natural populations of these organisms. To study this issue, population-based samples of 568 strains from Ontario, Canada; Finland; and Houston, Texas, were analyzed. Special attention was given to analysis of variation in prophage-encoded virulence gene content by a PCR-based method. Thirty and 29 distinct prophage-encoded virulence gene profiles were identified among pharyngitis and invasive infection isolates. Thirteen profiles, representing the majority of the strains, were shared between these two classes of isolates. Significant differences were observed in the frequency of occurrence of certain prophage toxin gene profiles and infection type. M28 strains are highly diverse in prophage-encoded virulence gene content and integration site, supporting the key concept that prophages are critical contributors to GAS genetic diversity and population biology. Nucleotide sequence variation in theemm gene (encodes M protein) was also examined. Only three allelic variants were identified in the hypervariable portion of theemm28 gene. All but one strain had the same inferred amino acid sequence in the first 100 amino acids of the mature M28 protein. In contrast, size differences in theemm28 gene and inferred protein due to variable numbers of C-terminal repeats were common. The presence of macrolide resistance genes (mefA ,ermB , andermTR ) was analyzed by PCR, and less than 2% of the strains were positive.