Tissue Tropisms in Group a Streptococcal Infections

Abstract

Group A Streptococcus (GAS) is a human-specific pathogen that is highly prevalent throughout the world. The vast majority of GAS infections lead to a mild disease involving the epithelial surfaces of either the throat or skin. The concept of distinct sets of ‘throat’ and ‘skin’ strains of GAS has long been conceived. From an ecological standpoint, the epithelium of the throat and skin are important because it is where the organism is most successful in reproducing and transmitting to new hosts. This article examines key features of the epidemiology, population biology and molecular pathogenesis that underlie the tissue site preferences for infection exhibited by GAS, with an emphasis on work from our laboratory on skin tropisms. Recombinational replacement with orthologous gene forms, following interspecies transfer, appears to be an important genetic step leading up to the exploitation of new niches by GAS.

High Incidence of Invasive Group A Streptococcus Disease Caused by Strains of Uncommon emm Types in Thunder Bay, Ontario, Canada

“…However, strains of types emm83 and emm101 were found in a discrete branch of the phylogenetic tree that also contains emm53 strain Alab49 and emm14 strain HSC5 (Fig. 4F) (13,21,22). Type emm83 strain NGAS327 clustered tightly with emm83 strain Percentage of strains…”

“…(C) Tissue tropism of iGAS strains isolated from 2011 to 2013 in Thunder Bay, Toronto/Peel, and the rest of Ontario. Significant differences were observed for skin, throat, and generalist groups (defined according to references [11][12][13] between Thunder Bay and Toronto/Peel plus the rest of Ontario (chi-square test, P Ͻ 0.05). Unknown, nontypeable strains.…”

“…However, TBD public health authorities continue to observe rates of iGAS disease incidence that are approximately 2 to 4 times the provincial average. Associations between strains of specific emm types and tropism for different tissues have long been described (11)(12)(13). Markers of niche specificity defining skin, throat, and generalist (i.e., those commonly isolated from both skin and throat infections) GAS strains have been proposed based on the arrangement of the emm and emm-like chromosomal region and on the presence of different variants of the mga, rofA, or nra loci (encoding standalone transcriptional regulators), the pilus-encoding FCT loci, and the sof gene (encoding a serum opacity factor) (13).…”

SpyAD, a Moonlighting Protein of Group A Streptococcus Contributing to Bacterial Division and Host Cell Adhesion

“…Bacterial growth and host-pathogen interactions are therefore key steps toward a successful infection. To achieve this, GAS has evolved a broad repertoire of virulence factors, which exert their functions at distinct infection stages (4)(5)(6)(7) and are regulated during different growth phases and under diverse environmental conditions (2). Among them, cell surface components mediating GAS adherence to eukaryotic cells.…”

“…Among them, cell surface components mediating GAS adherence to eukaryotic cells. Different types of putative streptococcal adhesins and their cellular receptors have been identified, and extensive studies on their functional activity and expression regulation have provided important clues on their contribution to GAS tissue tropism and pathogenesis mechanisms (5)(6)(7).…”