Natural Variant of Collagen-Like Protein A in Serotype M3 Group A Streptococcus Increases Adherence and Decreases Invasive Potential

Group A Streptococcus (GAS) predominantly exists as a colonizer of the human oropharynx that occasionally breaches epithelial barriers to cause invasive diseases. Despite the frequency of GAS carriage, few investigations into the contributory molecular mechanisms exist. To this end, we identified a naturally occurring polymorphism in the gene encoding the streptococcal collagen-like protein A (SclA) in GAS carrier strains. All previously sequenced invasive serotype M3 GAS possess a premature stop codon in the sclA gene truncating the protein. The carrier polymorphism is predicted to restore SclA function and was infrequently identified by targeted DNA sequencing in invasive strains of the same serotype. We demonstrate that a strain with the carrier sclA allele expressed a full-length SclA protein, while the strain with the invasive sclA allele expressed a truncated variant. An isoallelic mutant invasive strain with the carrier sclA allele exhibited decreased virulence in a mouse model of invasive disease and decreased multiplication in human blood. Further, the isoallelic invasive strain with the carrier sclA allele persisted in the mouse nasopharynx and had increased adherence to cultured epithelial cells. Repair of the premature stop codon in the invasive sclA allele restored the ability to bind the extracellular matrix proteins laminin and cellular fibronectin. These data demonstrate that a mutation in GAS carrier strains increases adherence and decreases virulence and suggest selection against increased adherence in GAS invasive isolates.     

Hematologic changes during and after cardiopulmonary bypass and their relationship to the bleeding time and nonsurgical blood loss.

The hemostatic dysfunction induced by cardiopulmonary bypass is due, in part, to a platelet dysfunction evidenced by a postoperative extension of the bleeding time; it leads to increased postoperative blood loss and morbidity. This study, which was conducted in 85 patients undergoing cardiopulmonary bypass, was designed to characterize the hematologic changes during and after cardiopulmonary bypass and to elucidate the relationships between these changes, the extension of the bleeding time, and the magnitude of the postoperative nonsurgical blood loss. Variables were measured before, during, and 2, 24, 48, and 72 hours after cardiopulmonary bypass. Univariate and multivariate analyses were performed with either the 2-hour postbypass bleeding time or the 4-hour postbypass blood loss as the dependent variables. The reversal of the extension of the bleeding time in the postoperative period was accompanied by a significant increase in the mean platelet volume and by a significant increase in the level of thromboxane B2 measured in the blood shed from the site of the bleeding time determination. The postoperative bleeding time correlated with the postoperative blood loss, and both parameters were dependent on the duration of cardiopulmonary bypass. In addition, the postoperative bleeding time correlated with the skin temperature and the plasma level of D-dimer, while the postoperative blood loss also correlated with temperature and the plasma levels of C3. These data establish a direct relationship between the postoperative bleeding time, the postoperative blood loss, and temperature. They indicate that the reversal of the postoperative extension of the bleeding time is due in part to rewarming and to the release of larger platelets into the circulation, and they suggest that hyperfibrinolysis and complement activation may play an important role in the cardiopulmonary bypass-induced platelet dysfunction.     

Molecular-weight distribution in the activated-monomer polymerization of ethylene oxide. Mechanistic implications

The mechanism of the activated-monomer polymerization of ethylene oxide catalyzed by protic acids was investigated by means of an analysis of the molecular-weight distribution curves from the polymers obtained. The results suggest that polymer ether groups participate in the polymerization by forming hydrogen-bonded complexes and tertiary oxonium cations in the reaction with the activated monomer, both being intermediates of the propagation reactions.     

Solid-phase radioimmunoassay for the detection of rotavirus.

A solid-phase radioimmunoassay method has been developed for the detection of rotavirus in the form of a purified antigen and in stool. The parameters of the radioimmunoassay were examined and optimized to give high sensitivity and same-day results. Compared with electron microscopy, the assay is up to 10 times as sensitive for detection of the virus in stool and up to 128 times as sensitive for detection of a purified virus antigen. In a field study on stool specimens it was at least as efficient as electron microscopy.     

Spread of old and new clones of epidemic methicillin-resistant Staphylococcus aureus in Poland

Objective: To study the relatedness among methicillin-resistant Staphylococcus aureus (MRSA) isolates originating from two regions of Poland using different epidemiologic typing methods.
Methods: Forty-five MRSA isolates (19 from Warsaw and 26 from the Grajewo region) were collected between 1995 and 1996. For phenotypic epidemiologic analysis, antimicrobial susceptibility testing (AST) with a panel of 19 antibiotics was performed. For genotypic epidemiologic analysis, pulsed-field gel electrophoresis (PFGE) of Smal-digested chromosomal DNA, restriction endonuclease analysis of plasmid (REAP) DNA digested by Hin dIII, random amplification of polymorphic DNA (RAPD) and binary typing (BT) of genomic DNA by hybridization with five different RAPD-generated strain-specific DNA probes, were used.
Results: Six clusters of clonally related strains were found among the MRSA isolates analyzed. Three of these, identified in both regions, were related to previously described Polish epidemic clones, designated HeEMRSA-Pol1 (heterogeneously methicillin resistant—18 isolates) and HoEMRSA-Pol1 (homogeneously resistant—two clones, six isolates each). The remaining three clones, identified in the Grajewo region only, are previously undescribed. One of these, represented by 11 isolates, appears to be new epidemic heterogeneous MRSA clone (HeEMRSA-Pol2). Results of PFGE and BT in general showed good correlation, and, in some cases, RAPD using AP1 and AP7 primers could discriminate between isolates belonging to single PFGE or BT types. Broad AST and REAP can provide useful additional information concerning relatedness.
Conclusion: Evidence for the spread of previously recognized epidemic MRSA clones in Poland and the presence of a new epidemic heterogeneously resistant clone of MRSA in hospitals outside Warsaw is documented.     

Phase Variation of Campylobacter jejuni 81-176 Lipooligosaccharide Affects Ganglioside Mimicry and Invasiveness In Vitro

The outer cores of the lipooligosaccharides (LOS) of many strains of Campylobacter jejuni mimic human gangliosides in structure. A population of cells of C. jejuni strain 81-176 produced a mixture of LOS cores which consisted primarily of structures mimicking GM(2) and GM(3) gangliosides, with minor amounts of structures mimicking GD(1b) and GD(2). Genetic analyses of genes involved in the biosynthesis of the outer core of C. jejuni 81-176 revealed the presence of a homopolymeric tract of G residues within a gene encoding CgtA, an N-acetylgalactosaminyltransferase. Variation in the number of G residues within cgtA affected the length of the open reading frame, and these changes in cgtA corresponded to a change in LOS structure from GM(2) to GM(3) ganglioside mimicry. Site-specific mutation of cgtA in 81-176 resulted in a major LOS core structure that lacked GalNAc and resembled GM(3) ganglioside. Compared to wild-type 81-176, the cgtA mutant showed a significant increase in invasion of INT407 cells. In comparison, a site-specific mutation of the neuC1 gene resulted in the loss of sialic acid in the LOS core and reduced resistance to normal human serum but had no affect on invasion of INT407 cells.     

Counter-immunoelectro-osmophoresis for the detection of infantile gastroenteritis virus (orbi-group) antigen and antibody.

A moderatley sensitive, rapid, and economical test scheme for the detection of infantile gastroenteritis virus (IGV) in stool or antibody in serum has been developed and evaluated. The test scheme with minor modifications was an adaptation of a counter-immunoelectro-osmophoresis system we once used for the detection of hepatitis B antigen. Large numbers of stool samples may be screened during half a working day for the presence of IGV using reference antiserum to IGV prepared in guinea-pigs. Serological studies of a diagnostic but not epidemiological nature may also be performed with equal facility by this same test scheme using highly purified IGV antigen derived from stool.     

Polylysine binding to unphosphorylated smooth muscle myosin enhances formation and stabilizes myosin filaments in vitro

Previously, we demonstrated that positively charged polylysine, our model for biological polyamines, activates the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin and shifts the myosin conformation from the folded 10S to linear 6S form. These effects of polylysine were reversed by the oppositely charged heparin (Szymanski et al. (1993) Am J Physiol 265, C379). In the present report, we provide further information on polylysine binding to smooth muscle myosin, and test the hypothesis that polylysine binding to unphosphorylated myosin involves filament formation. To relate the effects of polylysine on contractility in smooth muscle to physiologically relevant material, we investigated the ability of naturally occurring positively charged polyamines, histones, cadaverine, putrescine and spermidine to activate the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin. Our data show that polylysine binding to individual unphosphorylated myosin molecules stimulates formation of myosin filaments. Polylysine also interacts with myosin filaments, causing enhancement of their size and the numbers, and this could be reversed by heparin. Polylysine binding to myosin filaments made them more resistant to disassembly by high salt concentrations (KCl) or ATP. Naturally occurring polyamines in millimolar concentrations activate the Mg2+ ATPase activity of unphosphorylated smooth muscle myosin. We suggest that the electrostatic interactions between naturally occurring positively charged polyamines and unphosphorylated smooth muscle myosin may play a role in stabilization of thick filament structurein situ.