PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Streptococcus pyogenes”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources
PubMed2001

Spontaneous mutations in the CsrRS two-component regulatory system of Streptococcus pyogenes result in enhanced virulence in a murine model of skin and soft tissue infection.

CsrS/CsrR is a 2-component system in Streptococcus pyogenes that negatively regulates hyaluronic capsule and several exotoxins. To detect spontaneous mutations in csrRS, mucoid and large colony variants of M1 strain MGAS166 were isolated from experimental murine skin infections. By use of complementation with a csrRS(+) plasmid, relevant mutations were also detected in 7 of 12 human clinical isolates. The presence of spontaneous mutants in mouse infection was associated with larger, more necrotic lesions. Most spontaneous changes in CsrR resulted from single amino acid substitutions, whereas most csrS mutations were frameshift or nonsense mutations. In 2 instances, IS1548 insertions were found in csrS. Experimental inoculation of mixtures of wild-type (wt) and csrRS(-) bacteria yielded larger, more necrotic lesions than did either strain at twice the inoculum, which suggests that these variants may exhibit pathogenic synergy. Spontaneous emergence of csrRS(-) mutants in vivo enhances the virulence of wt bacteria and increases severity of murine skin infection.

Amino Acid Substitution↗
PubMedDate not supplied

[Antimicrobial sensitivity and characterization of Streptococcus pyogenes strains isoleated from a scarlatina outbreak].

OBJECTIVE: To evaluate the in vitro activities of 13 antimicrobial agents against 47 group A Streptococcus pyogenes (GAS) strains, and to determine the presence of genes encoding streptococcal pyrogenic exotoxin A (SpeA) and the M-protein serotypes. MATERIALS AND METHODS: A cross-sectional study was conducted at Centro de Salud Dr. José Castro Villagrana, during a scarlet fever outbreak occurring between December 1999 and January 2000, among 137 children at Colegio Espíritu de América. Minimum Inhibitory Concentrations (MICs) were obtained by the semiautomated microdilution method. Automated DNA sequencing was used for analysis of sequence variation in genes encoding the M protein, and SpeA. RESULTS: All strains were sensitive to betalactams and clindamycin. Six (12.7%) were resistant to erythromycin. The M2 type was the most frequently isolated GAS (27); almost all (96%) bacteria with the SpeA gene had the gene encoding the M2 protein. CONCLUSIONS: The recent resurgence of GAS infections calls for molecular epidemiology research and studies on the sensitivity to macrolides and beta-lactams.

Adolescent↗
PubMed2006

IdeS, a highly specific immunoglobulin G (IgG)-cleaving enzyme from Streptococcus pyogenes, is inhibited by specific IgG antibodies generated during infection.

IdeS, a recently discovered cysteine proteinase secreted by the important human pathogen Streptococcus pyogenes, interferes with phagocytic killing by specifically cleaving the heavy chain of immunoglobulin G. The fact that the enzyme targets one of the key molecules of the adapted immune response raised the question of whether an antibody response against IdeS could inhibit, i.e., neutralize, enzyme activity. Paired acute- and convalescent-phase serum samples from patients with pharyngotonsillitis (n = 10), bacteremia (n = 7), and erysipelas (n = 4) were analyzed. Antibodies with the ability to neutralize IdeS enzymatic activity were already found in two-thirds of acute-phase sera. However, patients who seroconverted to IdeS, in particular patients with pharyngotonsillitis and erysipelas, developed specific antibodies during convalescence with an increased capability to efficiently neutralize the enzymatic activity of IdeS. Also, the presence of neutralizing antibodies decreased the ability of IdeS to mediate bacterial survival in human immune blood. In patients with bacteremia, several acute-phase sera contained neutralizing antibodies, but no correlation was found to severity or outcome of invasive infections. Still, the fact that the human immune response targets the enzymatic activity of IdeS supports the view that the enzyme plays an important role during streptococcal infection.

Amino Acid Sequence↗
PubMed2006

Nucleotide usage, synonymous substitution pattern, and past recombination in genomes of Streptococcus pyogenes.

We examined (1) five variables summarizing nucleotide usage at synonymous sites; (2) pairwise patterns of nucleotide substitution among five genomes of Streptococcus pyogenes in order to examine the extent to which these variables are associated with past recombination events. Predicted prophage genes of MGAS10394 were characterized by an average pattern of nucleotide usage at synonymous sites that was distinct from that seen at most other genes. Ribosomal protein genes also showed a distinctive pattern, but one that differed from prophage genes in several key respects. The six most anomalous genes with respect to synonymous substitution in pairwise comparisons among the genomes included four prophage genes; these six genes were characterized by unusually high values of d(S), suggesting that these genes had different evolutionary histories from those of the other shared genes in the genome. This hypothesis was supported by phylogenetic analyses, which revealed phylogenies inconsistent with that of the majority of genes. Eighty-nine genes outside prophage regions were found to resemble prophage genes with respect to nucleotide content and the pattern of synonymous substitution, suggesting that these genes may have been involved in horizontal gene transfers. Although prophage genes do show distinctive patterns of nucleotide composition, the results indicated that those patterns were not in themselves sufficient to distinguish all known prophage genes from other genes. On the other hand, nucleotide content, when suitably measured, can form one of a set of biological indicators that can be used to identify candidate genes for horizontal gene transfer.

Amino Acid Substitution↗
PubMed1998

Genetic inactivation of an extracellular cysteine protease (SpeB) expressed by Streptococcus pyogenes decreases resistance to phagocytosis and dissemination to organs.

Streptococcal pyrogenic exotoxin B (SpeB), a conserved cysteine protease expressed by virtually all Streptococcus pyogenes strains, has recently been shown to be an important virulence factor (S. Lukomski, S. Sreevatsan, C. Amberg, W. Reichardt, M. Woischnik, A. Podbielski, and J. M. Musser, J. Clin. Invest. 99:2574-2580, 1997). Genetic inactivation of SpeB significantly decreased the lethality of a serotype M49 strain for mice and abolished the lethality of a serotype M3 strain after intraperitoneal (i.p.) injection. In the present study, a wild-type M3 isolate and an M3 speB mutant derivative were used to investigate the mechanism responsible for altered virulence. Following i.p. injection, the mutant and wild-type strains induced virtually identical cellular inflammatory responses, characterized largely by an influx of polymorphonuclear leukocytes (PMNs). In addition, the mutant and wild-type strains rapidly entered the blood and were recovered from all organs examined. However, significantly fewer (P < 0.05) CFUs of the isogenic mutant derivative than of the wild-type parent strain were recovered from blood and organs. PMNs effectively cleared the M3 speB mutant from the peritoneum by 22 h, thereby sparing the host. In contrast, the wild-type M3 strain continued to replicate intraperitoneally and had the ability to kill phagocytes. This process allowed the wild-type strain to continuously disseminate, resulting in host death. Our results indicate that genetic inactivation of the cysteine protease decreased the resistance of the mutant to phagocytosis and impaired its subsequent dissemination to organs. These results provide insight into the detrimental effect of SpeB inactivation on virulence.

Animals↗
PubMed1971

Cell wall polysaccharide biosynthesis by membrane fragments from Streptococcus pyogenes and stabilized L-form.

The formation and composition of a cell wall rhamnose-containing polysaccharide by membrane fragments from Streptococcus pyogenes and its stabilized L-form were compared. Also, the effect of prior treatment on the ability of coccal whole-cell and membrane fragments to incorporate radioactivity from thymidine diphosphate-(14)C-rhamnose, and the results of subsequent attempts to remove labeled polysaccharide from such membranes are given. L-form membrane fragments were capable of only 10% uptake of (14)C-rhamnose from this nucleotide as compared with streptococcal membranes. However, once bound, both membrane fragments polymerized rhamnose to the same extent. These findings tend to negate the almost complete lack of polymeric rhamnose within the intact L-form as being due to the absence of membrane enzymes necessary for the transfer of rhamnose from a suitable precursor to membrane acceptor sites or enzymes responsible for rhamnose polymerization. Degradation of labeled rhamnose polysaccharide after isolation from coccal membranes by mild acid hydrolysis showed muramic acid and glucosamine to be attached. This same polysaccharide from L-form membrane fragments was devoid of amino sugars. These data suggest the possible involvement of amino sugars in the attachment of cell wall polymeric rhamnose to the streptococcal cytoplasmic membrane. The absence of attached amino sugars to rhamnose polysaccharide from L-form membrane fragments is discussed in terms of this organism's continued inability for new cell wall formation. The isolation, from streptococcal membrane fragments, of a polysaccharide containing rhamnose and amino sugars common to at least two different streptococcal cell wall-type polymers was demonstrated.

Amino Sugars↗
PubMed1994

Sensitivity of Staphylococcus aureus and Streptococcus pyogenes isolated from skin infections in 1992 to antimicrobial agents.

We studied the efficacy of antimicrobial agents against Staphylococcus aureus (S. aureus) and Streptococcus pyogenes (S. pyogenes) isolated from skin infections in 1992. For S. aureus, we measured the minimum inhibitory concentrations (MICs) of the following 10 drugs: methicillin (DMPPC), cefaclor (CCL), gentamicin (GM), erythromycin (EM), clindamycin (CLDM), minocycline (MINO), vancomycin (VAN), fusidic acid (FA), ofloxacin (OFLX) and nadifloxacin (NDFX); for S. pyogenes, we determined the MICs of the following 9 drugs: ampicillin (ABPC), amoxicillin (AMPC), cefpodoxime proxetil (CPDX-PR), erythromycin (EM), clindamycin (CLDM), minocycline (MINO), norfloxacin (NFLX), of loxacin (OFLX) and nadifloxacin (NDFX). These drugs are frequently used to treat skin infections, either systemically or topically. NDFX is a new synthetic fluoroquinolone, recently developed for use as a topical acne medication in Japan. It is used NDFX for acne, but not for skin infections. There were no strains of S. aureus resistant to NDFX, VAN or FA. The resistance (> or = 12.5 micrograms/ml) of S. aureus was highest to GM and lowest to OFLX. Four strains of methicillin-resistant (> or = 12.5 micrograms/ml) S. aureus (MRSA) were found. In contrast, no resistant strains of S. pyogenes were found except to MINO. Only two strains of S. pyogenes were susceptible to MINO. The sensitivity of S. pyogenes to ABPC, AMPC, CPDX-PR, EM and CLDM was very good. All the strains were susceptible at a MIC below > or = 0.05 microgram/ml. However, the S. pyogenes strains were not very sensitive to the new quinolones, especially NFLX. We concluded that penicillins, cephalosporins and macrolides are still effective against streptococcal infections.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗
PubMed2006

Streptococcus pyogenes bacteria modulate membrane traffic in human neutrophils and selectively inhibit azurophilic granule fusion with phagosomes.

We recently reported that the human pathogen Streptococcus pyogenes of the M1 serotype survives and replicates intracellularly after being phagocytosed by human neutrophils. These data raised the possibility that the generation of reactive oxygen metabolites by neutrophils, and the release of microbicidal molecules from their azurophilic and specific granules into phagosomes, can be modulated by S. pyogenes bacteria expressing surface-associated M and/or M-like proteins. We now demonstrate, using flow cytometry, immunofluorescence microscopy and transmission electron microscopy, that live wild-type S. pyogenes, after internalization by human neutrophils, inhibits the fusion of azurophilic granules with phagosomes. In contrast, azurophilic granule-content is efficiently delivered to phagosomes containing bacteria not expressing M and/or M-like proteins. Also, when heat-killed wild-type bacteria are used as the phagocytic prey, fusion of azurophilic granules with phagosomes is observed. The inhibition caused by live wild-type S. pyogenes is specific for azurophilic granule-phagosome fusion, because the mobilization of specific granules and the production of reactive oxygen species are induced to a similar extent by all strains tested. In conclusion, our results demonstrate that viable S. pyogenes bacteria expressing M and M-like proteins selectively prevent the fusion of azurophilic granules with phagosomes.

Azure Stains↗
PubMed1995

Genetic diversity and relationships among Streptococcus pyogenes strains expressing serotype M1 protein: recent intercontinental spread of a subclone causing episodes of invasive disease.

Chromosomal diversity and relationships among 126 Streptococcus pyogenes strains expressing M1 protein from 13 countries on five continents were analyzed by multilocus enzyme electrophoresis and restriction fragment profiling by pulsed-field gel electrophoresis. All isolates were studied for the presence of the gene encoding streptococcal pyrogenic exotoxin A by PCR. Strain subsets were also examined by automated DNA sequencing for allelic polymorphism in genes encoding M protein (emm), streptococcal pyrogenic exotoxin A (speA), streptokinase (ska), pyrogenic exotoxin B (interleukin-1 beta convertase) (speB), and C5a peptidase (scp). Seven distinct emm1 alleles that encode M proteins differing at one or more amino acids in the N-terminal variable region were identified. Although substantial levels of genetic diversity exist among M1-expressing organisms, most invasive disease episodes are caused by two subclones marked by distinctive multilocus enzyme electrophoretic profiles and pulsed-field gel electrophoresis restriction fragment length polymorphism (RFLP) types. One of these subclones (ET 1/RFLP pattern 1a) has the speA gene and was recovered worldwide. Identity of speA, emm1, speB, and ska alleles in virtually all isolates of ET 1/RFLP type 1a means that these organisms share a common ancestor and that global dispersion of this M1-expressing subclone has occurred very recently. The occurrence of the same emm and ska alleles in strains that are well differentiated in overall chromosomal character demonstrates that horizontal transfer and recombination play a fundamental role in diversifying natural populations of S. pyogenes.

Amino Acid Sequence↗
PubMed2005

[Annual changes in antimicrobial susceptibility and macrolide resistance of Streptococcus pyogenes from 1995 through 2004].

This aim of this study was to reveal annual changes in antibiotic susceptibility, especially the macrolide susceptibility of Streptococcus pyogenes. A total of 755 strains of S. pyogenes were clinicaly isolated from throat swabs of children from 1995 through 2004 in Chiba Municipal Kaihin Hospital. All isolates were fully susceptible to benzylpenicillin, cefotaxim and cefaclor. The rate of resistance to erythromycin (EM) was over 10% every year after 2001 and 19% in 2004, and the rate of high resistance (MIC > or =16 microg/mL) has been increasing. A significant increase in EM resistance was observed over a 10-year period. There were 118 strains (15.6%) that persisted after treatment with beta-lactams. In the past few years it has been discovered that some S. pyogenes can be internalized by human cells of respiratory tract origin and survive within them. Since beta-lactams do not reach high intracellular concentrations, this ability of S. pyogenes may be related to treatment failure. Since macrolides can enter eukaryotic cells and remain active in intracellular compartments, they will be effective for these S. pyogenes. In case of pharyngitis which againist treatment with beta-lactams, there is a possibility macrolides are effective. Macrolides may be effective in pharyngitis resistant to treatment with beta-lactams. However, macrolide resistance is not rare, susceptibility must be tested.

Anti-Bacterial Agents↗
PubMed1991

Identification of Streptococcus pyogenes proteins that bind to rabbit kidney in vitro and in vivo.

Proteins were extracted from the surface of a nephritogenic strain of Streptococcus pyogenes M12 and tested for binding to rabbit kidney using indirect immunofluorescence and enzyme-linked immunoassays. Streptococcal antigens bound in vitro in a fine linear pattern to basal laminae of glomeruli, Bowman's capsule, and tubules. Perfusion of rabbit kidney in vivo with streptococcal components resulted in focal and segmental fine granular staining of glomerular capillaries. Three streptococcal proteins (43, 31 and 9 kDa) were recovered from renal tissue that was pretreated in vitro with S. pyogenes extract. Streptococcal components bound in vitro to heparan sulfate, heparin, laminin and collagen IV but only weakly or not at all to fibronectin, bovine serum albumin or dextran sulfate. Affinity chromatography of bacterial extracts on heparin-agarose produced a 9 kDa streptococcal protein (pI 9.5) which bound to kidney basement membranes in vitro and in isolated perfused kidneys. Several additional strains of group A streptococci were found to contain the 9 kDa cationic protein. This bacterial protein, when released into the blood by the bacterium during infection, may contribute to the pathogenesis of streptococcus-associated nephritides in man.

Animals↗
PubMed1986

Cytotoxic and antitumor activity of a soluble fraction of Streptococcus pyogenes against S180 sarcoma cells.

A fraction (60F) having cytotoxic and antitumor activities was obtained from cell-free extract of group A Streptococcus pyogenes by precipitating with 50% to 60% saturated ammonium sulfate. 60F showed cytotoxic activity inhibiting the uptake of 3H-thymidine by S180 sarcoma cells and enhancing 51Cr-release from 51Cr-labeled cells. 60F showed also antitumor activity, depressing tumor growth and prolonging lives of mice bearing S180 sarcoma cells.

Adjuvants, Immunologic↗
PubMed1993

The in vitro antibacterial activity of ceftriaxone against Streptococcus pyogenes is unrelated to penicillin-binding protein 4.

The in vitro activities of penicillin and ceftriaxone were compared against 29 strains of Streptococcus pyogenes with the result that ceftriaxone showed greater activity than penicillin. The morphological changes induced by 1/2 and 1x MIC concentrations of penicillin and ceftriaxone, respectively, were very similar using scanning electron microscopy. Competitive binding studies using 'cold' penicillin or ceftriaxone as inhibitors of radiolabeled penicillin binding demonstrated that ceftriaxone had a very low affinity for penicillin binding protein (PBP) 4 compared to that of penicillin. Since ceftriaxone had greater antibacterial activity, this suggests that PBP 4 may not be important to the in vitro activity of ceftriaxone. In contrast, the IC50 for ceftriaxone was much lower (> 200 fold) for PBPs 2 and 3 compared to PBP 4, suggesting greater avidity of these high molecular mass PBPs for ceftriaxone. These data may at least in part explain the superior in vitro activity of ceftriaxone compared to penicillin against S. pyogenes. These data, together with the observation that PBP 1 was saturated at a lower concentration of penicillin than any of the other PBPs, suggest that the inhibition of PBPs 1, 2, and 3 mediates the bactericidal activity of beta-lactam antibiotics against group A streptococci.

Bacterial Proteins↗
PubMed2003

Evaluating the American Academy of Pediatrics diagnostic standard for Streptococcus pyogenes pharyngitis: backup culture versus repeat rapid antigen testing.

OBJECTIVE: The American Academy of Pediatrics recommends that all negative rapid diagnostic tests for Streptococcus pyogenes pharyngitis be backed up by culture, which creates a dilemma for clinicians who must make treatment decisions without complete diagnostic information at the time of visit. The use of a follow-up serial rapid antigen test instead of a follow-up culture would provide a more timely result. METHODS: Two swabs were collected from children who were suspected of having S pyogenes pharyngitis. Each swab was used for a culture and an OSOM Ultra Strep A Test rapid antigen test. The gold standard of comparison was defined as the identification of S pyogenes on either of the 2 culture plates. Three diagnostic strategies were evaluated: a single rapid antigen test, a rapid antigen test with follow-up rapid antigen test (rapid-rapid), and a rapid antigen test with follow-up culture (rapid-culture). RESULTS: A total of 210 (23.7%) of 887 throat cultures with matched data were identified with S pyogenes. A single rapid antigen test had a sensitivity of 87.6% (95% confidence interval [CI]: 83.2%-92.1%), the sensitivity of the rapid-rapid follow-up was 91.4% (95% CI: 87.6%-95.2%), and the sensitivity of the rapid-culture follow-up was 95.7% (95% CI: 93.0%-98.5%), which was significantly higher than the others. As shown in Fig 1, when these test strategies were evaluated on a subgroup with clinical symptoms commonly associated with S pyogenes pharyngitis, the sensitivities all increased and were no longer significantly different. None of the strategies reliably exceeded a 95% sensitivity threshold. CONCLUSIONS: The American Academy of Pediatrics strategy for S pyogenes detection in children with pharyngitis, requiring a backup culture for those with negative antigen tests, was not exceeded by any other test strategy; however, a rapid-rapid diagnostic strategy may approximate it with the use of judicious clinical selection of patients.

Antigens, Bacterial↗
PubMed2006

Macrolide prescriptions and erythromycin resistance of Streptococcus pyogenes.

This study shows a significant association between the number of macrolide prescriptions reimbursed by the Italian National Health Service and resistance of Streptococcus pyogenes to erythromycin in children from a region in northern Italy with high prevalence of erythromycin resistance. Recent prescription of a macrolide (especially azithromycin) is a predictor of erythromycin resistance, as well as a possible risk factor for resistance at a community level.

Adolescent↗
PubMed1993

Radiometric study on the invasion capability of Streptococcus pyogenes A49 L-forms in tissue cultures.

By a radiometric method using C14 labelled amino acid mixture it was established that the Streptococcus pyogenes A49 L-forms cells invade tissue cultures MK and F in a similar degree as parent bacterium cells. The L-form cells are not able to enter the HeLa and Pulmo tissue culture cells but the parent bacterium cells produce well expressed peak of isotope take-up at the 8th hour of the observation.

Animals↗
PubMed1992

Oral erythromycin prophylaxis against Streptococcus pyogenes infection in penicillin-allergic military recruits: a randomized clinical trial.

Historically, military recruits have required benzathine penicillin G to prevent epidemics of Streptococcus pyogenes. In this randomized clinical trial, low-dose oral erythromycin was evaluated as an alternative for prophylaxis against group A beta-hemolytic streptococci in penicillin-allergic recruits. US Marine Corps recruits (186) reporting penicillin allergy were randomly given either oral erythromycin (250 mg twice a day) or a vitamin (one tablet daily) for 60 days. Evidence of infection was defined as a two-dilution rise in anti-streptolysin O titer. The erythromycin group had a significantly lower risk of S. pyogenes infection than did the vitamin group (relative risk 0.44; 95% confidence interval, 0.22-0.89). There was no significant difference among the treatment groups in isolation of group A beta-hemolytic streptococci from throat cultures. Low-dose oral erythromycin appears as effective as benzanthine penicillin G in preventing S. pyogenes infection.

Administration, Oral↗