1,721,018 research outputs found
The dcw cluster of Streptococcus pneumoniae: a model to evaluate new conserved targets among Gram-positive pathogens through genomics
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Characterization of Streptococcus pneumoniae FtsA conditional lethal mutants reveals unexpected features of cell division in Gram-positive pathogens of ovococcal shape
No full textRate of penetration of cefetamet, cefixime, cefuraxime and cefaclor in different strains of Enterobacteriacae
No full textThe Aeromonas hydrophyla cphA gene: molecular heterogeneity among class B metallo-β-lactamases
Full text linkAn Aeromonas hydrophila gene, named cphA, coding for a carbapenem-hydrolyzing metallo-beta-lactamase, was cloned in Escherichia coli by screening an Aeromonas genomic library for clones able to grow on imipenem-containing medium. From sequencing data, the cloned cphA gene appeared able to code for a polypeptide of 254 amino acids whose sequence includes a potential N-terminal leader sequence for targeting the protein to the periplasmic space. These data were in agreement with the molecular mass of the original Aeromonas enzyme and of the recombinant enzyme produced in E. coli, evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude beta-lactamase preparations followed by renaturation treatment for proteins separated in the gel and localization of protein bands showing carbapenem-hydrolyzing beta-lactamase activity by a modified iodometric technique. The deduced amino acid sequence of the CphA enzyme showed regions of partial homology with both the beta-lactamase II of Bacillus cereus and the CfiA beta-lactamase of Bacteroides fragilis. Sequence homologies were more pronounced in the regions encompassing the amino acid residues known in the enzyme of B. cereus to function as ligand-binding residues for the metal cofactor. The CphA enzyme, however, appeared to share a lower degree of similarity with the two other enzymes, which, in turn, seemed more closely related to each other. These results, therefore, suggest the existence of at least two molecular subclasses within molecular class B metallo-beta-lactamases
The mechanism of staphylococci resistance to methicillin: a critical analysis of dominant opinions
No full textHelicobacter pylori: enemy, commensal or, sometimes, friend?
Full text linkHelicobacter pylori is a Gram-negative ε-proteobacterium that colonizes about 50% of humans. Some pertinent characteristics are that it can survive the acid of the stomach, produces urease to neutralize it and is motile due to apical flagella. Not surprisingly given its wide distribution, it has long colonized mankind and its genome encodes many features that allows this. Consequently, it frequently has a persistent lifelong association with humans and, differently from most pathogens that are transmitted horizontally, it is preferentially transmitted vertically, often from mother to child. A variety of genes and polymorphisms, both in H pylori and in humans, mediate the complex host-bacterium relationship, and can also determine if and what pathologies will be triggered by the species. H. pylori is naturally transformable, very recombinogenic and has a high mutation rate. Microbiota studies of the stomach have shown it to be an important species with a potentially regulatory role for the gastric microbial community. Likewise, epidemiological work has suggested that, while it clearly increases the risk of peptic ulcers and gastric cancer in some populations, it is also associated with lower risk of esophageal cancer and several other important pathologies. More recently, antibacterial resistant strains have been isolated, posing a problem for public health officials who called for its eradication. Hence, study of H. pylori and how it interacts with us can help revealing mutualistic or pathogenic interactions and the immune response in the digestive niche
Hard tissue response to argon plasma cleaning/sterilisation of customised titanium abutments versus 5-second steam cleaning: results of a 2-year post-loading follow-up from an explanatory randomised controlled trial in periodontally healthy patients.
No full textPurpose: The aim of this triple-blinded randomised controlled trial was to test if argon plasma cleaning/ sterilisation of customised abutments can affect peri-implant marginal bone levels when compared to 5 seconds of steam cleaning.
Materials and methods: A total of 20 consecutive periodontally healthy patients requiring single implant-supported restorations in the maxillary premolar or anterior area were selected. All patients received a single implant. At abutment connection, customised abutments were randomly allocated to control (subjected only to usually adopted steam cleaning, CG) and test groups (subjected to plasma cleaning/sterilisation, TG). Abutments were screwed in at 32 Ncm, provisional restorations adapted and periapical radiographs were taken using customised film holders. Two weeks later, definitive restorations were placed. Patients were followed-up for 2 years post-loading. Outcome measures were implant/crown success, complications, periapical marginal bone level changes on periapical standardised radiographs, and microbiological analyses of the abutments after customisation and cleaning procedures but before connection. Comparisons between groups were performed by independent sample t tests (significance threshold of P ≤ 0.05).
Results: No patient dropped out 2 years after loading. The presence of bacterial growth (staphylococci, including Staphylococcus aureus) was observed only on the CG abutments. No implant failed and no complications occurred. After 2 years of prosthetic loading, radiographic analysis revealed a statistically significantly higher mean bone loss for the CG group (mean difference 0.4 mm; 95% CI 0.08-0.73; P = 0.018).
Conclusions: This study suggests that removal of contaminants from titanium abutments using plasma of argon can allow for better bone level maintenance when compared to 5-second steam cleaning of titanium abutments. It is therefore important to use cleaned and sterilised customised abutments in patients
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