Streptococcus pyogenes (group A streptococcus) strains may express several distinct ®bronectinbinding proteins (FBPs) which are considered as major streptococcal adhesins. Of the FBPs, SfbI was shown in Šitro to promote internalization of the bacterium into host cells and has been implicated in persistence. In the tropical Northern Territory, where group A streptococcal infection is common, multiple genotypes of the organism were found among isolates from invasive disease cases and no dominant strains were observed. To determine whether any FBPs is associated with invasive disease propensity of S. pyogenes, we have screened streptococcal isolates from bacteraemic and necrotizing fasciitis patients and isolates from uncomplicated infections for genetic endowment of 4 FBPs. No difference was observed in the distribution of sfbII, fbp54 and sfbI between the blood isolates and isolates from uncomplicated infection. We conclude that the presence of sfbI does not appear to promote invasive diseases, despite its association with persistence. We also show a higher proportion of group A streptococcus strains isolated from invasive disease cases possess prtFII when compared to strains isolated from non-invasive disease cases. We suggest that S. pyogenes may recruit different FBPs for different purposes.
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SUMMARYStreptococcus pyogenes (group A streptococcus) strains may express several distinct fibronectinbinding proteins (FBPs) which are considered as major streptococcal adhesins. Of the FBPs, SfbI was shown in itro to promote internalization of the bacterium into host cells and has been implicated in persistence. In the tropical Northern Territory, where group A streptococcal infection is common, multiple genotypes of the organism were found among isolates from invasive disease cases and no dominant strains were observed. To determine whether any FBPs is associated with invasive disease propensity of S. pyogenes, we have screened streptococcal isolates from bacteraemic and necrotizing fasciitis patients and isolates from uncomplicated infections for genetic endowment of 4 FBPs. No difference was observed in the distribution of sfbII, fbp54 and sfbI between the blood isolates and isolates from uncomplicated infection. We conclude that the presence of sfbI does not appear to promote invasive diseases, despite its association with persistence. We also show a higher proportion of group A streptococcus strains isolated from invasive disease cases possess prtFII when compared to strains isolated from non-invasive disease cases. We suggest that S. pyogenes may recruit different FBPs for different purposes.
Streptococcus pyogenes (Group A streptococcus) interacts with host fibronectin via a number of distinct surface components. The streptococcal serum opacity factor (SOF) is a cell-surface protein of S. pyogenes which causes opalescence of human serum and mediates bacterial binding to fibronectin. In this study, hexahistidyl-tagged fusion proteins encompassing full-length SOF, and domains of SOF encompassing opacity factor activity and fibronectinbinding regions, were used in the characterization of the Aboriginal immune response to SOF. Anti-SOF serum IgG responses were found to be significantly higher (P T 0 0001) in Aboriginal adults and children when compared to a nonAboriginal adult group. The Aboriginal immune response against the fibronectin-binding region of SOF was significantly reduced when compared to the response against the whole SOF protein and N-terminal domains examined in this study (P T 0 001). This pattern of immune response was also observed in rabbits immunized with recombinant SOF. Comparison of the deduced amino acid sequence of SOF from a number of common Australian isolates with other SOF sequences revealed that the N-terminus of SOF exhibits sequence similarity values ranging from 42 9 % to 96 5 %. The C-terminus containing the fibronectin-binding domain and membrane-spanning regions was more highly conserved, exhibiting sequence similarity values ranging from 84 6 % to 100 % within the fibronectin-binding repeats. These data suggest that the immune response against SOF is directed toward the variable N-terminus of the SOF protein. Phylogenetic analysis indicated that the sof genes of S. pyogenes do not exhibit geographical variation.
Streptococcus pyogenes isolates from a tropical region and a subtropical region of Australia with high and low incidences of severe streptococcal diseases, respectively, were analyzed for speA, speB, and speC gene distributions and NAD-glycohydrolase expression. No direct correlation of these characteristics with a propensity to cause invasive diseases was observed
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