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At least 1,063 records · Page 59Linked to original sources
PubMed2000

Mutation in csrR global regulator reduces Streptococcus pyogenes internalization.

Transposon (Tn 916) mutagenesis was employed to identify genes in group A streptococcus (GAS) that are involved in bacterial internalization by epithelial cells. One mutant displayed significantly reduced internalization efficiency and was therefore selected for further characterization. The mutant harbored a single Tn 916 insertion in csr, a genetic locus encoding a two-component regulatory system. Mutations in csr were found to derepress hyaluronic acid (HA) capsule synthesis. Since capsule expression has been previously reported to interfere with internalization of GAS, it was possible that the transposon exerted its inhibitory effect either by derepression of capsule synthesis, or by another mechanism. To study the effect of the csr mutation on bacterial internalization, isogenic mutants deficient in either csrR, hasA or both were generated. The hasA mutant adhered to and internalized into HEp-2 cells significantly better than the parent and the csrR mutant strains. The internalization efficiency of the double mutant (csrR(-)/hasA(-)) was reduced by seven-fold compared to that of the hasA mutant. These findings suggest that csrR affects streptococcal entry by modulating capsule expression as well as by another, yet unknown, mechanism.

Bacterial Adhesion↗
PubMed2005

Association between resistance to erythromycin and the presence of the fibronectin binding protein F1 gene, prtF1, in Streptococcus pyogenes isolates from German pediatric patients.

A total of 301 German pediatric group A streptococcus isolates were screened for the presence of macrolide resistance and the fibronectin binding protein F1 gene (prtF1) encoding an adhesin and cell invasiveness protein. The prtF1 gene was present significantly more often among macrolide-resistant isolates. The majority of these were not clonally related.

Adhesins, Bacterial↗
PubMed2005

Contribution of natural killer cells to the pathogenesis of septic shock induced by Streptococcus pyogenes in mice.

Natural killer (NK) cells are critical components of the innate immune system and have been implicated in the pathogenesis of septic shock. In the present study, the relative contribution of NK cells to the development of Streptococcus pyogenes-induced septic shock was investigated in a mouse model of group A streptococcal infection that resembles the development of this condition in humans. C3H/HeN mice were depleted of NK cells by in vivo administration of anti-asialo ganglio-N-tetraosylceramide antibodies and then were examined for their response to infection with S. pyogenes. NK cell-depleted mice exhibited increased survival times and slower development of disease during group A streptococcal infection than did nondepleted control mice. The augmented resistance to S. pyogenes observed in NK cell-depleted mice was associated with serum levels of proinflammatory cytokines such as interferon- gamma, interleukin (IL)-12, and IL-6 during the early phase of infection that were much lower than those detected in nondepleted control mice. NK cell-deficient mutant mice were also more resistant to S. pyogenes than were the corresponding control mice. We conclude that NK cells, by amplifying the inflammatory response, significantly contribute to the progression of S. pyogenes-induced septic shock.

Animals↗
PubMed1996

Possible role for a polysaccharide antigen shared between Streptococcus pyogenes and S. mutans in the pathogenesis of poststreptococcal glomerulonephritis.

Streptococcus mutans has been shown to share a polysaccharide (PS) antigen with S. pyogenes strains isolated from patients with acute poststreptococcal glomerulonephritis (PSGN), using a monoclonal antibody f-77 reactive with the PS. To investigate the pathogenetic role of the shared PS in PSNG, experimental nephritis was induced in animals. Rats were immunized thrice with heat-killed cells of S. mutans or S. pyogenes, followed by an intravenous injection of live cells of S. pyogenes. Histologic examination showed that both animal groups had comparable degrees of diffuse proliferative nephritis characterized by immune deposits. The shared PS antigen was detected in glomeruli of all nephritic rats by immunofluorescence using monoclonal antibody f-77. Furthermore, all nephritic rats had an elevated antibody titer to the shared PS antigen. These results suggest that prior sensitization (infections such as dental caries) to S. mutans modulates immune responses to subsequent S. pyogenes infections and induces immune-complex disease (PSGN) through the shared PS antigen.

Acute Disease↗
PubMed1991

Possible role of Streptococcus pyogenes in mucocutaneous lymph node syndrome. XII. Variable responses of platelets in MCLS seem to be explainable by streptococcal pyrogenic exotoxin.

As a model system for mucocutaneous lymph node syndrome (MCLS), we have advocated and used mice which had been rendered tolerant to Streptococcus pyogenes-associated antigens by neonatal infection with group A beta-hemolytic streptococci, because these mice have shown a variety of peculiar bioimmunological characteristics bearing a striking resemblance to those of MCLS patients. The results of our current investigations reaffirmed the reliability of the animal model by indicating that mice subjected to neonatal infection with S. pyogenes, or inoculation with streptococcal pyrogenic exotoxin (SPE) in Freund's adjuvant, were perfect counterparts of patients with MCLS on account of their platelet activation and hyperaggregability in response to provocative treatment, which are familiar findings in this disease.

Animals↗
PubMed2006

Identification and biochemical characterization of a eukaryotic-type serine/threonine kinase and its cognate phosphatase in Streptococcus pyogenes: their biological functions and substrate identification.

A eukaryotic-type signaling system in group A Streptococcus (GAS) was identified and characterized. This system comprises primarily the products of two co-transcribed genes, a eukaryotic-type Ser/Thr kinase (SP-STK) and phosphatase (SP-STP) and their endogenous substrate histone-like protein (SP-HLP). Enzyme activities of SP-STK and SP-STP primarily depended on Mn(2+). The site on the substrate for reversible phosphorylation by these enzymes was found to be only the threonine residue. Using specific antibodies generated against these proteins, SP-STK was found to be membrane-associated with its N-terminal kinase domain facing the cytoplasm and its C-terminal repeat domain outside the membrane and cell-wall associated. Further, SP-STP, primarily a cytoplasmic protein, was found to be a major secretory protein of GAS and essential for bacterial survival. Three isogenic mutants, lacking either the entire SP-STK, or one of its two domains, were found displaying distinct pleiotropic effects on growth, colony morphology, cell division/septation, surface protein/virulence factor expression, bacterial ability to adhere to and invade human pharyngeal cells, and resist phagocytosis by human neutrophils. In addition to these properties, the ability of these three proteins to modulate the expression of the major virulence factors, the M protein and the capsule, indicates that these proteins are structurally and functionally distinct from the kinases and phosphatases described in other microorganisms and play a key role in GAS pathogenesis.

Amino Acid Sequence↗
PubMed2003

Identification of new candidate vaccine antigens made by Streptococcus pyogenes: purification and characterization of 16 putative extracellular lipoproteins.

Putative extracellular lipoproteins made by group A Streptococcus (GAS) are the focus of this study, which was designed to identify new candidate vaccine antigens. Bioinformatic analysis of a serotype M1 GAS strain identified 30 open-reading frames encoding putative lipoproteins. The genes encoding the mature form of 29 of these proteins were cloned, and 16 recombinant proteins were overexpressed in Escherichia coli and purified to apparent homogeneity. The genes encoding these 16 proteins were highly conserved in GAS strains for which genome sequence data are available (serotypes M1, M3, M5, M12, M18, and M28). Mice inoculated subcutaneously with GAS and humans with GAS pharyngitis and invasive infections seroconverted to most of the 16 recombinant proteins, which indicates that these lipoproteins were produced during infection. The blood of mice actively immunized with 5 of the 16 recombinant proteins had significantly (P<.05) increased growth-inhibitory activity, compared with the blood of unimmunized mice, which identified these proteins as potential new vaccine candidates.

Amino Acid Sequence↗