A Long-Term Survey of Methicillin-Resistant Staphylococcus aureus in the Oral Cavity of Children

Methicillin-resistant Staphylococcus aureus (MRSA), an indigenous bacteria in healthy people, often causes nosocomial infections. If the host human becomes compromised, MRSA can cause a serious infection. The long-term colonization of MRSA increases this risk. The purpose of this study was to demonstrate the incidence of S. aureus and MRSA colonization in the oral cavities of healthy children, and to examine the stability of identical strains of MRSA over a long-term period. Fourteen children were examined in two stages (first stage: 1987–88, second stage: 1992–93). Five of the 14 children were negative for S. aureus in both stages, seven children were positive in both stages and two children were positive in only the second stage. The children who were colonized with S. aureus in the first stage always harbored the bacteria in the second stage. Of the seven children that were positive for S. aureus in both stages, three persisted in carrying MRSA. We compared two MRSA strains isolated from the same children in both stages by coagulase typing, antibiogram typing and DNA fingerprinting. In two children, the strains showed the same coagulase types, similar antibiograms and similar DNA fragment profiles. These data strongly suggest that identical strains of MRSA persisted in the oral cavities for more than five years, and that the oral cavity can serve as a reservoir for MRSA with the potential to cause nosocomial infections.     

Amplification of rfbE and fliC Genes by Polymerase Chain Reaction for Identification and Detection of Salmonella Serovar Enteritidis,Dublin and Gallinarum-Pullorum

Polymerase chain reaction (PCR) primers for O9 antigen (rfbE) and phase 1 flagellin antigen (fliC) were designed for the rapid identification and detection of Salmonella serovar Enteritidis and Dublin. The rfbE primer pairs selectively amplified the rfbE region of group O9 Salmonella serovars. The fliC primer pairs amplified the DNAs of g,m and g,p-type flagellar antigen; Salmonella serovar Enteritidis, Dublin, and Essen. However, DNA from flagellar-negative Salmonella serovar Gallinarum-Pullorum was also amplified. The sensitivity of PCR primer pairs was 10 CFU/assay by boiled DNA preparation and 10² CFU/assay by proteinase K-treated DNA preparation.     

Autotrophic carbon dioxide fixation inAcidianus brierleyi

The autotrophic CO₂ fixation pathway inAcidianus brierleyi, a facultatively anaerobic thermoacidophilic archaebacterium, was investigated by measuring enzymatic activities from autotrophic, mixotrophic, and heterotrophic cultures. Contrary to the published report that the reductive tricarboxylic acid cycle operates inA. brierleyi, the enzymatic activity of ATP:citrate lyase, the key enzyme of the cycle, was not detected. Instead, activities of acetyl-CoA carboxylase and propionyl-CoA carboxylase, key enzymes of the 3-hydroxypropionate cycle, were detected only whenA. brierleyi was growing autotrophically. We conclude that a modified 3-hydroxypropionate pathway operates inA. brierleyi.Abbreviations TCA tricarboxylic acid - BV Benzyl viologen     

Glial cell lineage in vivo in the mouse cerebellum

Glial cells of the cerebellum originate from cells of the ventricular germinative layer, but their lineage has not been fully elucidated. For studying the glial cell lineage in vivo by retrovirus-mediated gene transfer, we introduced a marker retrovirus into the ventricular germinative layer of embryonic day 13 mice. In the resulting adult cerebella, virus-labeled glial cells were grouped in discrete clusters, and statistical analysis showed that these clusters represented clones in high probability. Of 71 of the virus-labeled glial clusters, 33 clusters were composed of astrocytes/Bergmann glia, 10 were composed of only white matter astrocytes, and 24 were composed of only oligodendrocytes. No glial clusters contained virus-labeled neurons. These results suggest that astrocytes/Bergmann glia, white matter astrocytes and oligodendrocytes immediately arise from separate glial precursors: these three glial lineages may diverge in the course of cerebellar development.     

Requirement of Atypical Protein Kinase Cλ for Insulin Stimulation of Glucose Uptake but Not for Akt Activation in 3T3-L1 Adipocytes

Phosphoinositide (PI) 3-kinase contributes to a wide variety of biological actions, including insulin stimulation of glucose transport in adipocytes. Both Akt (protein kinase B), a serine-threonine kinase with a pleckstrin homology domain, and atypical isoforms of protein kinase C (PKCζ and PKCλ) have been implicated as downstream effectors of PI 3-kinase. Endogenous or transfected PKCλ in 3T3-L1 adipocytes or CHO cells has now been shown to be activated by insulin in a manner sensitive to inhibitors of PI 3-kinase (wortmannin and a dominant negative mutant of PI 3-kinase). Overexpression of kinase-deficient mutants of PKCλ (λKD or λΔNKD), achieved with the use of adenovirus-mediated gene transfer, resulted in inhibition of insulin activation of PKCλ, indicating that these mutants exert dominant negative effects. Insulin-stimulated glucose uptake and translocation of the glucose transporter GLUT4 to the plasma membrane, but not growth hormone- or hyperosmolarity-induced glucose uptake, were inhibited by λKD or λΔNKD in a dose-dependent manner. The maximal inhibition of insulin-induced glucose uptake achieved by the dominant negative mutants of PKCλ was ~50 to 60%. These mutants did not inhibit insulin-induced activation of Akt. A PKCλ mutant that lacks the pseudosubstrate domain (λΔPD) exhibited markedly increased kinase activity relative to that of the wild-type enzyme, and expression of λΔPD in quiescent 3T3-L1 adipocytes resulted in the stimulation of glucose uptake and translocation of GLUT4 but not in the activation of Akt. Furthermore, overexpression of an Akt mutant in which the phosphorylation sites targeted by growth factors are replaced by alanine resulted in inhibition of insulin-induced activation of Akt but not of PKCλ. These results suggest that insulin-elicited signals that pass through PI 3-kinase subsequently diverge into at least two independent pathways, an Akt pathway and a PKCλ pathway, and that the latter pathway contributes, at least in part, to insulin stimulation of glucose uptake in 3T3-L1 adipocytes.     

Hydration of vinyl ether groups by unsaturated glycoside hydrolases and their role in bacterial pathogenesis.

Many pathogenic microorganisms invade mammalian and/or plant cells by producing polysaccharide-degrading enzymes (lyases and hydrolases). Mammalian glycosaminoglycans and plant pectins that form part of the cell surface matrix are typical targets for these microbial enzymes. Unsaturated glycoside hydrolase catalyzes the hydrolytic release of an unsaturated uronic acid from oligosaccharides, which are produced through the reaction of matrix-degrading polysaccharide lyase. This enzymatic ability suggests that unsaturated glycoside hydrolases function as virulence factors in microbial infection. This review focuses on the molecular identification, bacterial distribution, and structure/function relationships of these enzymes. In contrast to general glycoside hydrolases, in which the catalytic mechanism involves the retention or inversion of an anomeric configuration, unsaturated glycoside hydrolases uniquely trigger the hydrolysis of vinyl ether groups in unsaturated saccharides but not of their glycosidic bonds.     

Neuraminidase of Corynebacterium diphtheriae

Neuraminidase activity has been found in a variety of strains of Corynebacterium diphtheriae, both toxinogenic and nontoxinogenic. The enzyme has been shown to be intracellular, possibly associated with the cytoplasmic membrane. Toxinogenic strains of the diphtheria bacillus, grown under conditions unsuitable for maximal toxin production, produce neuraminidase, and the enzyme has been purified from cells of the Park Williams no. 8 strain grown under such conditions. Diphtherial toxin and diphtherial neuraminidase have similar molecular weights and remain associated during column chromatography; immunochemically, and in their electrophoretic behavior, they appear distinct.