Ion conductivity through TEMPO-mediated oxidated and periodate oxidated cellulose membranes.

Cellulose in different forms is increasingly used due to sustainability aspects. Even though cellulose itself is an isolating material, it might affect ion transport in electronic applications. This effect is important to understand for instance in the design of cellulose-based supercapacitors. To test the ion conductivity through membranes made from cellulose nanofibril (CNF) materials, different electrolytes chosen with respect to the Hofmeister series were studied. The CNF samples were oxidised to three different surface charge levels via 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and a second batch was further cross-linked by periodate oxidation to increase wet strength and stability. The outcome showed that the CNF pre-treatment and choice of electrolyte are both crucial to the ion conductivity through the membranes. Significant specific ion effects were observed for the TEMPO-oxidised CNF. Periodate oxidated CNF showed low ion conductivity for all electrolytes tested due to an inhibited swelling caused by the crosslinking reaction.

Microrheology of novel cellulose stabilized oil-in-water emulsions.

Diffusing wave spectroscopy (DWS) is a powerful optical technique suitable to investigate turbid samples in a nondestructive and reproducible way, providing information on the static and dynamic properties of the system. This includes the relative displacement of emulsion droplets over time and changes in the viscoelastic properties. Here, novel and promising cellulose-based oil-in-water (O/W) emulsions were prepared and studied, for the first time, by DWS. Cellulose plays the role of a novel eco-friendly emulsifying agent. The hydrolysis time of cellulose was observed to affect the average size of the emulsion droplets and their stability; the longer the hydrolysis time, the more dispersed and stable the emulsions were found to be. Additionally, a good complementarity between the microrheology (DWS) and macrorheology (mechanical rheometer) data was found. Our work suggests that DWS is a highly attractive method to investigate the stability, aging and microrheology properties of cellulose-based emulsions, providing valuable insights on their microstructure. This technique is thus highly appealing for the characterization and design of novel emulsion formulations.

Mutually exclusive distribution of IS1548 and GBSi1, an active group II intron identified in human isolates of group B streptococci.

The present study shows that active, self-splicing group II intron GBSi1 is located downstream of the C5a-peptidase gene, scpB, in some group B streptococcus (GBS) isolates that lack insertion sequence IS1548. IS1548 was previously reported to be often present at the scpB locus in GBS isolated in association with endocarditis. Since none of 67 GBS isolates examined, 40 of which were of serotype III, harbored both IS1548 and GBSi1, these two elements are suggested to be markers for different genetic lineages in GBS serotype III. The DNA region downstream of scpB in GBS isolates harboring either GBSi1, IS1548, or none of these mobile elements was found to encode the laminin binding protein, Lmb, which shows sequence similarities to a family of streptococcal adhesins. IS1548 is inserted 9 bp upstream of the putative promoter for lmb, while the insertion site for GBSi1 is located 88 bp further upstream. Sequences highly similar to GBSi1 exist also in Streptococcus pneumoniae. An inverted repeat sequence, with features typical of transcription terminators, was identified immediately upstream of the insertion site for the group II intron both in the GBS and S. pneumoniae sequences. This motif is suggested to constitute a target for the GBS intron as well as for rather closely related introns in Bacillus halodurans, Pseudomonas alcaligenes, and Pseudomonas putida. When transcripts containing the GBSi1 intron were incubated at high concentrations of ammonium and magnesium, a major product with the expected length and sequence for the ligated exons was generated. Unlike, however, all members of group II investigated so far, the excised intron was in linear, rather than in a branched (lariat), form.

Opsonization of T1M1 group A Streptococcus: dynamics of antibody production and strain specificity.

A chemiluminescence method was used to study opsonization of group A Streptococcus (GAS) of serotype T1M1 in serum samples ("sera") obtained from Swedish patients with invasive and noninvasive GAS infection and from healthy blood donors. Acute-phase serum samples ("acute sera") generally demonstrated low ability to opsonize the patient's own GAS isolate, regardless of clinical manifestation. Only approximately 15% of serum samples obtained from healthy blood donors demonstrated high opsonic activity against a standard T1M1 strain. Opsonization of 62 T1M1 isolates (obtained during 1980-1998) by a single immune serum sample showed considerable variation; this indicates that high opsonic immunity may develop only against the infecting isolate or identical clones. T1M1 GAS isolated from 1987 through 1990 were better opsonized by the immune serum sample than were isolates obtained before 1987 or after 1990, a finding that suggests a temporal change of the surface properties that affect opsonization.

Genotyping of the capsule gene cluster (cps) in nontypeable group B streptococci reveals two major cps allelic variants of serotypes III and VII.

Forty group B Streptococcus (GBS) isolates obtained from Europe and the United States previously reported to be nontypeable (NT) by capsule serotype determination were subjected to buoyant density gradient centrifugation. From nearly half of the isolates capsule-expressing variants could be selected. For characterization of the remaining NT-GBS isolates, the capsule operon (cps) was amplified by the long-fragment PCR technique and compared by restriction fragment length polymorphism (RFLP) analysis. The patterns from serotype reference isolates (n = 32) were first determined and used as a comparison matrix for the NT-GBS isolates. Using two restriction enzymes, SduI and AvaII, cluster analysis revealed a high degree of similarity within serotypes but less than 88% similarity between serotypes. However, serotypes III and VII were each split in two distant RFLP clusters, which were designated III(1) and III(2) and VII(1) and VII(2), respectively. Among the isolates that remained NT after repeated Percoll gradient selections, two insertional mutants were revealed. Both were found in blood isolates and harbored insertion sequence (IS) elements within cpsD: one harbored IS1548, and the other harbored IS861. All other NT-GBS isolates could, by cluster analysis, be referred to different serotypes by comparison to the RFLP reference matrix. In pulsed-field gel electrophoresis of SmaI-restricted chromosomal DNA, patterns from allelic type 1 and 2 isolates were essentially distributed in separate clusters in serotypes III and VII. A covariation with insertion sequence IS1548 in the hylB gene was suggested for serotype III, since allelic type III(1) harboring IS1548 in hylB, clustered separately. The variation in serotype VII was not dependent on the presence of IS1548, which was not detected at any position in the type VII chromosome.

Magnetostatic image current and its application to an analytic identification of a current dipole inside a conducting sphere.

The image solution for the static magnetic field outside a conducting sphere with an internal current dipole is considered. The image current, which is a linear distribution of magnetic dipoles on the line segment between the dipole point and the center of the sphere, is derived by using the fact that the induced current does not have any contribution to the radial component of the magnetic field outside the sphere. The image is then used to obtain some explicit formulas for identifying the location and tangential moment of the primary current dipole. This explicit identification method is also tested with a real model for a patient's brain.

Allele substitution of the streptokinase gene reduces the nephritogenic capacity of group A streptococcal strain NZ131.

To investigate the role of allelic variants of streptokinase in the pathogenesis of acute poststreptococcal glomerulonephritis (APSGN), site-specific integration plasmids were constructed, which contained either the non-nephritis-associated streptokinase gene (skc5) from the group C streptococcal strain Streptococcus equisimilis H46A or the nephritis-associated streptokinase gene (ska1) from the group A streptococcal nephritogenic strain NZ131. The plasmids were introduced by electroporation and homologous recombination into the chromosome of an isogenic derivative of strain NZ131, in which the streptokinase gene had been deleted and which had thereby lost its nephritogenic capacity in a mouse model of APSGN. The introduction of a non-nephritis-associated allelic variant of streptokinase did not rescue the nephritogenic capacity of the strain. The mutant and the wild-type strains produced equivalent amounts of streptokinase. Complementation of the ska deletion derivative with the original ska allele reconstituted the nephritogenicity of wild-type NZ131. The findings support the hypothesis that the role of streptokinase in the pathogenesis of APSGN is related to the allelic variant of the protein.

The superantigenic activity of streptococcal pyrogenic exotoxin B is independent of the protease activity.

The nature of the mitogenic activity of pyrogenic streptococcal exotoxin B, also known as streptococcal cysteine protease, has been debated in the literature. Streptococcal exotoxin B has been shown to cleave interleukin-1beta precursor and create biologically active interleukin-1beta, a major cytokine mediating inflammation and shock. This activity could mimic the mitogenicity and cytokine release induced by superantigens in lymphocyte stimulating experiments. In this study, the protease activity of streptococcal exotoxin B was irreversibly inhibited by covalent binding of a tripeptide and the superantigenic properties of streptococcal exotoxin B were found not to be influenced by this inactivation. Native as well as protease-inactivated streptococcal exotoxin B was shown to stimulate T-cell proliferation without a need of metabolically active antigen presenting cells. Furthermore, streptococcal exotoxin B-induced T-cell proliferation was shown to require HLA-DQ since addition of HLA-DQ monoclonal antibodies totally inhibited the mitogenic activity of streptococcal exotoxin B, indicating that streptococcal exotoxin B, as other superantigens, makes direct contact with the T-cell receptor via HLA class II. The aim of this study was to characterize the relationship between the proteolytic and superantigenic properties of streptococcal exotoxin B.

Invasive group A streptococcal infections: T1M1 isolates expressing pyrogenic exotoxins A and B in combination with selective lack of toxin-neutralizing antibodies are associated with increased risk of streptococcal toxic shock syndrome.

Analysis of 132 group A streptococcal (GAS) isolates from 151 invasive episodes, including streptococcal toxic shock syndrome (STSS), from 1983 to 1995 showed great genetic variation by use of T serotyping in combination with restriction fragment length polymorphism. In contrast, genetically homogenous T1M1 isolates appeared in epidemic patterns with significantly increased risk of STSS. The speA gene, with the allelic variants speA2 and speA3 carried by the T1M1 and T3M3 serotypes, respectively, was strongly associated with STSS. Infection with a GAS isolate carrying speA, alcohol abuse, and malignancy recently treated with cytostatic drugs were factors independently related to STSS. Neutralization of SpeA lymphocyte mitogenicity was totally absent in sera from patients with STSS and low in sera from persons with uncomplicated bacteremia compared with levels in sera from uncomplicated erysipelas. Neutralization of SpeB was significantly lower in sera of patients with STSS than in sera from persons with bacteremia or erysipelas.

Characterization and nucleotide sequence of a Klebsiella oxytoca cryptic plasmid encoding a CMY-type beta-lactamase: confirmation that the plasmid-mediated cephamycinase originated from the Citrobacter freundii AmpC beta-lactamase.

Plasmid pTKH11, originally obtained by electroporation of a Klebsiella oxytoca plasmid preparation into Escherichia coli XAC, expressed a high level of an AmpC-like beta-lactamase. The enzyme, designated CMY-5, conferred resistance to extended-spectrum beta-lactams in E. coli; nevertheless, the phenotype was cryptic in the K. oxytoca donor. Determination of the complete nucleotide sequence of pTKH11 revealed that the 8,193-bp plasmid encoded seven open reading frames, including that for the CMY-5 beta-lactamase (blaCMY-5). The blaCMY-5 product was similar to the plasmidic CMY-2 beta-lactamase of K. pneumoniae and the chromosomal AmpC of Citrobacter freundii, with 99.7 and 97.0% identities, respectively; there was a substitution of phenylalanine in CMY-5 for isoleucine 105 in CMY-2. blaCMY-5 was followed by the Blc and SugE genes of C. freundii, and this cluster exhibited a genetic organization identical to that of the ampC region on the chromosome of C. freundii; these results confirmed that C. freundii AmpC was the evolutionary origin of the plasmidic cephamycinases. In the K. oxytoca host, the copy number of pTKH11 was very low and the plasmid coexisted with plasmid pNBL63. Analysis of the replication regions of the two plasmids revealed 97% sequence similarity in the RNA I transcripts; this result implied that the two plasmids might be incompatible. Incompatibility of the two plasmids might explain the cryptic phenotype of blaCMY-5 in K. oxytoca through an exclusion effect on pTKH11 by resident plasmid pNBL63.

Streptococcal DNase B is immunologically identical to superantigen SpeF but involves separate domains.

The previous suggestion that streptococcal superantigen SpeF might be identical to DNase B was confirmed in this study. Polyclonal SpeF-specific antisera were able to inhibit depolymerization of methyl-green DNA by DNase B. However, T-cell mitogenicity and nuclease activity appear to involve separate immune epitopes on SpeF, since sera with the capacity to neutralize the mitogenic activity of SpeF did not always inhibit the DNase activity.

Pathogenic mechanism of acute post-streptococcal glomerulonephritis.

Considerable knowledge has been accumulated regarding the characteristics of acute post-streptococcal glomerulonephritis (APSGN), and many attempts have been made to identify a streptococcal factor or factors responsible for triggering this disease. However, the pathogenic mechanism behind APSGN remains largely unknown. As glomerular deposition of C3 is generally demonstrated before that of IgG in the disease process, it is likely that the inflammatory response is initiated by renal deposition of a streptococcal product, rather than by deposition of antibodies or pre-formed immune complexes. During recent years, a number of streptococcal products have been suggested to be involved in the pathogenic process. In this review, possible roles of these factors are discussed in the context of the clinical and renal findings most often demonstrated in patients with APSGN. Streptokinase was observed to be required in order to induce signs of APSGN in mice, and a number of findings suggest that the initiation of the disease may occur as a result of renal binding by certain nephritis-associated variants of this protein. However, additional factors may be required for the development of the disease.

Epidemiological and clinical aspects of invasive group A streptococcal infections and the streptococcal toxic shock syndrome.

In a retrospective study of invasive infections due to group A Streptococcus (GAS) in Stockholm during 1987 to 1995, the average incidence per 100,000 residents per year was 2.3, varying between 3.7 per 100,000 (in 1988) and 1.3 per 100,000 (in 1993). Incidence was 1.8 in the age group of 0-4 years but otherwise increased by age, from 0.48 in the age group of 5-14 years to 6.1 among those over 65 years of age. A review of 151 invasive episodes occurring in 1983-1995 showed cyclic increases of infections due to T1M1-serotype strains during 1986-1990 and 1993-1995. The T1M1 serotype accounted for 27 (20%) of 135 available GAS strains. Streptococcal toxic shock syndrome (STSS) developed in 19 (13%) of the 151 episodes. The case fatality rate was 11% overall but 47% among patients with STSS. In a multivariate logistic regression model, STSS was associated with a history of alcohol abuse (odds ratio [OR], 6.3; P = .004) and infection with a T1M1 strain (OR, 6.7; P = .007). Case fatality was associated with age (OR, 14.5; P = .08), immunosuppression (OR, 4.7; P = .02), and STSS (OR, 21.5; P < .0001) but not with T1M1 infection. Hypotension was significantly associated with a fatal outcome, regardless of whether STSS developed (P < .0001).

Identification of two genes, cpsX and cpsY, with putative regulatory function on capsule expression in group B streptococci.

Two divergently transcribed open reading frames: cpsX and cpsY separated by a common regulatory region was identified upstream of the cpsA-D genes involved in polysaccharide capsule biosynthesis in group B streptococci (GBS). We suggest that these genes are involved in the regulation of capsule expression in GBS, since the CpsX protein shares sequence similarities with LytR of Bacillus subtilis, an attenuator of transcription while CpsY has similarity to a wide variety of members of the LysR family of transcriptional regulators. No deletions, insertions, DNA rearrangements, or apparent differences were discovered in the postulated regulatory genes when the gene region was compared in GBS with different capsule phenotypes. Thus, other yet unidentified gene loci may control capsule phase variation in GBS.

Identification of a novel insertion element, IS1548, in group B streptococci, predominantly in strains causing endocarditis.

Hyaluronidase has been postulated to be a virulence factor in group B streptococci (GBS). No hyaluronidase activity was found in 15 of 50 GBS isolates from adults studied. Most of these hyaluronidase-negative strains belonged to serotype III. In strains lacking hyaluronidase activity, an insertion of 1317 nucleotides was found in the hyaluronidase gene. The fragment was cloned and sequenced and found to have characteristics of a novel insertion sequence, designated IS1548. As well as in GBS serotype III, this sequence was found in 3 of 6 serotype II isolates and in all 10 group A streptococcal strains (GAS) tested. Homologies were found with repeated sequences in Streptococcus pneumoniae and with H repeats in Escherichia coli. All GBS strains harboring IS1548 and some GAS strains had one copy of IS1548 located downstream of the C5a peptidase gene. IS1548 was present in 9 of 13 GBS isolates from blood in endocarditis patients and in 3 of 22 vaginally colonizing strains.

Streptokinase as a mediator of acute post-streptococcal glomerulonephritis in an experimental mouse model.

Group A streptococcal infections are sometimes followed by the inflammatory kidney disease acute post-streptococcal glomerulonephritis (APSGN). To test the importance of streptokinase in the pathogenesis of this disease, isogenic strains of the nephritis isolate NZ131, differing only in the ability to produce streptokinase of the nephritis-associated ska1 genotype, were used for infection in a mouse tissue cage model for APSGN. Streptokinase production was found to be a prerequisite for the capacity of the strain to induce APSGN in mice. In addition, streptokinase was demonstrated in the kidneys of mice infected with the nephritogenic NZ131 and EF514 strains. After infection with the nonnephritogenic strain S84, neither streptokinase nor C3 deposition were observed. Deposition of streptokinase in the glomeruli was detected as soon as 4 days after infection. These findings provide support for the hypothesis that streptokinase initiates the nephritis process by glomerular deposition, which leads to local activation of the complement cascade. Detection of streptokinase in kidney tissue increased with the degree of glomerular hypercellularity. Thus, the severity of the pathological process may be a reflection of the degree of streptokinase deposition.

Identification of domains involved in superantigenicity of streptococcal pyrogenic exotoxin F (SpeF).

A series of 11 synthetic peptides of 30 amino acids, each with 10 amino acids overlap which spanned the entire sequence of streptococcal pyrogenic exotoxin F (SpeF), were employed in proliferation studies on human peripheral blood mononuclear cells (PBMCs). Regions 41-70, 141-170 and 181-210 were identified as important for SpeF-induced lymphocyte activation. Secondary structure predictions of these peptides showed similarities to regions in other superantigens known to be important for T cell mitogenicity. Furthermore, antisera specific to peptides covering amino acids 1-70 and 181-228 were able to inhibit SpeF-induced mitogenicity by 25% when pre-incubated with SpeF prior to PBMC activation.

The role of household contacts in the transmission of group A streptococci.

The intrafamilial spread and recurrence of group A beta-haemolytic streptococci (GAS) infections was investigated. The evaluation was based on 114 patients and their families treated with penicillin for 5 days and followed for 1 month. GAS of the same T-type as that of the isolate from the index case were found in other family members in 33% of the families. Genetic finger-printing using RFLP was performed on 33 of the isolates. The mothers dominated among the index cases, 40 patients experienced recurrences, 27 of them were clinical 28 recurrences occurred within 10 days after the end of treatment. Of 20 T-typed patients with early clinical treatment failures, infected family members were detected in 16 families (p < 0.001). In 19% of the patients GAS could be isolated from the nose. These patients had more ill family members than did other patients. An extensive intrafamilial streptococcal spread was found. Most recurrences of GAS pharyngotonsillitis after penicillin treatment are probably due to "ping pong" infection from family members.

An experimental model for acute poststreptococcal glomerulonephritis in mice.

A number of factors have been implicated in the pathogenesis of acute poststreptococcal glomerulonephritis (APSGN). The lack of a reliable animal model has made it difficult to further examine the role of these factors in the pathogenetic process. In this report, we present a tissue cage model in mice for the study of APSGN. Morphological and immunohistological changes in the kidney, resembling those of APSGN in man, were induced at high frequency in the experimental model after infection with group A streptococcal nephritis isolates. Nephritis-associated strain induced hypercellularity, occlusion of capillaries, and C3 deposition at high frequencies compared to the changes induced in animals infected with a non-nephritis-associated strain and non-infected controls. In animals infected with a nephritis isolate, hematuria and proteinuria were also detected. If penicillin treatment was initiated on the third day of infection, the development of the nephritis process was prevented. Streptokinase, as well as preabsorbing antigen and streptococcal pyrogenic exotoxin B (SpeB), have been implicated in the pathogenesis of APSGN. These proteins, as well as SpeA and SpeF, were detected in the fluids of the infectious focus, regardless of the origin of the strains and whether or not glomerulonephritis was seen. Antibodies to streptokinase were evoked in the majority of the infected animals. This immune response did not correlate with the nephritic process since hypercellularity was also seen in animals which lacked detectable streptokinase antibodies. The results show that the mouse tissue cage model can be used to study APSGN and to evaluate factors involved in the pathogenesis of the disease.