178,344 research outputs found
Guidelines for reporting novel mecA gene homologues
No full textMethicillin-resistant staphylococci are disseminated all over the world and are frequent causes of health care- and community-associated infections. Methicillin-resistant strains typically carry the acquired mecA gene that encodes a low-affinity penicillin-binding protein (PBP), designated PBP2a or PBP2′. In most strains, mecA is part of a chromosomally integrated mobile genetic element called staphylococcal cassette chromosome mec (SCCmec). The mecA gene is widely disseminated among Staphylococcus aureus and other staphylococcal species, and its expression is essential for the methicillin-resistant phenotype. Recently, mecA gene homologues that are only distantly related to mecA have been identified in the genomes of staphylococci and some related bacterial species (Table 1). So far, four groups of mecA homologues have been described based on their degree of homology to the earliest identified mecA gene. We believe that this diversity warrants a new naming system based on phylogenetic principles which can also serve as a guideline for the reporting of additional novel mecA homologues that may be identified in the future
Genotyping of methicillin-resistant Staphylococcus aureus by assaying for the presence of variable elements associated with mecA
No full textThe region surrounding mecA in methicillin-resistant Staphylococcus aureus (MRSA) is highly variable. We describe an approach for the rapid genotyping of MRSA by assaying for the presence or absence of variable or mobile elements previously shown to be associated with the mecA region
Investigation of the Presence of mecA and mecC Genes and Antibiotic Resistance Profiles in Methicillin-Resistant Staphylococcus aureus Strains Isolated from Clinical Samples
No full textObjective: Methicillin-resistant Staphylococcus aureus (MRSA) is widely regarded as one of the most frequent bacteria, causing a wide range of infections in humans and animals. MRSA is associated with significant morbidity and mortality in many parts of the world. The aim of this study was to determine the molecular identification, antibiotic resistance profiles, and presence of mecA and mecC genes of MRSA strains isolated from clinical specimens at Siirt Training and Research Hospital.
Methods: In our study, we isolated 20 coagulase positive S. aureus strains from patients admitted to our hospital between July 2020-July 2021. Antibiotic susceptibility tests were carried out on the bacteria that were isolated and identified by culturing various clinical samples. The mecA and mecC genes were then examined by polymerase chain reaction (PCR) using the universal primers mecA-F-mecA-R and mecC-F-mecC-R following MRSA had been identified in the cultures from the clinical samples. To identify the isolated S. aureus strains by 16S ribosomal ribonucleic acid (rRNA) gene analysis, polymerase chain reaction (PCR) amplification was conducted using universal primers 68f and 518r.
Results: We isolated and identified 20 coagulase positive S. aureus strains from patients admitted to our hospital. According to the 16S rRNA gene sequences, the strains isolated in this this study, exhibited high similarity (99%-100%) to the 16S rRNA genes of S. aureus strains listed in GenBank (https://www.ncbi.nlm.nih.gov/genbank/). While the mecA gene was found in 18 of 20 strains, none of the strains had the mecC gene. A high percentage of MRSA was found to be penicillin resistant (75%). In conclusion, 20 MRSA strains were isolated from various clinical specimens. Eighteen of these strains were also identified molecularly by 16S rRNA sequence analysis.
Conclusion: The results of this study confirmed the significance of the 16S rRNA, mecA, and mecC genes in MRSA identification and highlighted the increasing frequency of MRSA in Türkiy
Proyecto de análisis de rentabilidad de instalación autónoma fotovoltaica para alimentar los servicios auxiliares de estación de metro y aparcamiento
No full textProyecto confidencial (Riunet)Meca Rojas, R. (2016). Proyecto de análisis de rentabilidad de instalación autónoma fotovoltaica para alimentar los servicios auxiliares de estación de metro y aparcamiento. https://riunet.upv.es/handle/10251/70074.Archivo delegad
Rapid Microarray-Based Identification of Different mecA Alleles in Staphylococci
No full textTo screen isolates and to identify mecA alleles, published mecA sequences were analyzed, and a microarray for the rapid discrimination of mecA alleles was designed. A GenBank analysis yielded 135 full-length gene sequences annotated as mecA. These sequences clustered into 32 different alleles corresponding to 28 unique amino acid sequences and to 15 distinct hybridization patterns on this microarray. A collection of 78 clinical and veterinary isolates of Staphylococcus spp. was characterized using this assay. Nine of the 15 expected patterns, as well as one as-yet-unknown pattern, were identified. These patterns were detected in various epidemic methicillin-resistant Staphylococcus aureus strains, in S. pseudintermedius, and in coagulase-negative species such as S. epidermidis, S. fleurettii, or S. haemolyticus. There was no correlation between the different mecA hybridization patterns and the SCCmec type. Determination of MICs showed that mecA alleles corresponding to only four of these nine patterns were associated with -lactam resistance. The mecA alleles that did not confer ß-lactam resistance were largely restricted to coagulase-negative staphylococci of animal origin, such as S. sciuri and S. vitulinus. Because of the diversity of sequences and the different impact on ß-lactam susceptibility, the existence of different mecA alleles needs to be taken into account when designing diagnostic assays for the detection of mecA
Species-dependent hemodynamic effects of adenosine A<sub>3</sub>-receptor agonists IB-MECA and Cl-IB-MECA
No full text The purpose of this study was to compare the hemodynamic effects of the adenosine A3-receptor agonists N 6-(3-iodobenzyl)-9-[5-(methylcarbamoyl)-β-d-ribofuranosyl]adenine (IB-MECA) and 2-chloro- N 6-(3-iodobenzyl)-9-[5-(methylcarbamoyl)-β-d-ribofuranosyl]adenine (Cl-IB-MECA) in isolated rat and rabbit hearts and in the intact, open-chest pig. Isolated hearts perfused with Krebs-Henseleit buffer at a constant pressure (70 mmHg) were treated with 50 nM of either IB-MECA or Cl-IB-MECA. Neither IB-MECA nor Cl-IB-MECA altered ventricular function or heart rate in the isolated rat and rabbit hearts, and neither agent altered coronary flow in the rabbit. However, 2 min of IB-MECA treatment in the isolated rat heart increased coronary flow by 25%, an effect that did not exhibit tachyphylaxis. The IB-MECA-induced coronary dilation was only partially attenuated by the adenosine A3-receptor antagonist MRS-1191 (50 nM). IB-MECA-induced coronary dilation was completely blocked by the adenosine A2a-receptor antagonist 7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine (Sch-58261, 50 nM). Cl-IB-MECA (50 nM) did not increase coronary flow in the rat, but 100 nM did increase flow by 18%. In pentobarbital sodium-anesthetized pigs IB-MECA (5 μg/kg iv) decreased systemic blood pressure and increased pulmonary artery pressure, effects that did exhibit tachyphylaxis. These results illustrate that adenosine A3-receptor agonists produce species-dependent effects, which in the rat heart appear to be caused by adenosine A2a-receptor activation. </jats:p
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Synthesis of low-loss metamaterials with negative index in the visible domain
No full text[EN] Over the last decade, negative index media have attracted much attention due to their potential applications, especially the possibility of constructing superlenses. However, achieving high-performance negative-index metamaterials at visible frequencies, where this kind of media could find many applications, still remains a challenge. In this article, we provide a brief overview of the main routes for the implementation of metamaterials with negative index in this band, with a special focus on the so-called fishnet metamaterial. We pay particular attention to a specific fishnet configuration that recently allowed for the experimental demonstration of a low-loss and polarization-insensitive negative-index band in the visible regime.The author would like to thank R. Ortuno for useful discussions. Financial support from project CONSOLIDER EMET CSD2008-00066 is also acknowledged.García Meca, C. (2013). Synthesis of low-loss metamaterials with negative index in the visible domain. Modern Physics Letters B. 27(15). https://doi.org/10.1142/S0217984913300111S271
Evidence for the evolutionary steps leading to mecA-mediated β-lactam resistance in staphylococci.
No full textThe epidemiologically most important mechanism of antibiotic resistance in Staphylococcus aureus is associated with mecA-an acquired gene encoding an extra penicillin-binding protein (PBP2a) with low affinity to virtually all β-lactams. The introduction of mecA into the S. aureus chromosome has led to the emergence of methicillin-resistant S. aureus (MRSA) pandemics, responsible for high rates of mortality worldwide. Nonetheless, little is known regarding the origin and evolution of mecA. Different mecA homologues have been identified in species belonging to the Staphylococcus sciuri group representing the most primitive staphylococci. In this study we aimed to identify evolutionary steps linking these mecA precursors to the β-lactam resistance gene mecA and the resistance phenotype. We sequenced genomes of 106 S. sciuri, S. vitulinus and S. fleurettii strains and determined their oxacillin susceptibility profiles. Single-nucleotide polymorphism (SNP) analysis of the core genome was performed to assess the genetic relatedness of the isolates. Phylogenetic analysis of the mecA gene homologues and promoters was achieved through nucleotide/amino acid sequence alignments and mutation rates were estimated using a Bayesian analysis. Furthermore, the predicted structure of mecA homologue-encoded PBPs of oxacillin-susceptible and -resistant strains were compared. We showed for the first time that oxacillin resistance in the S. sciuri group has emerged multiple times and by a variety of different mechanisms. Development of resistance occurred through several steps including structural diversification of the non-binding domain of native PBPs; changes in the promoters of mecA homologues; acquisition of SCCmec and adaptation of the bacterial genetic background. Moreover, our results suggest that it was exposure to β-lactams in human-created environments that has driven evolution of native PBPs towards a resistance determinant. The evolution of β-lactam resistance in staphylococci highlights the numerous resources available to bacteria to adapt to the selective pressure of antibiotics
mecA locus diversity in methicillin-resistant staphylococcus aureus isolates in Brisbane, Australia, and the development of a novel diagnostic procedure for the Western Samoan Phage Pattern Clone
No full textAn emerging public health phenomenon is the increasing incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections that are acquired outside of health care facilities. One lineage of community-acquired MRSA (CA-MRSA) is known as the Western Samoan phage pattern (WSPP) clone. The central aim of this study was to develop an efficient genotyping procedure for the identification of WSPP isolates. The approach taken was to make use of the highly variable region downstream of mecA in combination with a single nucleotide polymorphism (SNP) defined by the S. aureus multilocus sequence typing (MLST) database. The premise was that a combinatorial genotyping method that interrogated both a highly variable region and the genomic backbone would deliver a high degree of informative power relative to the number of genetic polymorphisms interrogated. Thirty-five MRSA isolates were used for this study, and their gene contents and order downstream of mecA were determined. The CA-MRSA isolates were found to contain a truncated mecA downstream region consisting of mecA-HVR-IS431 mec-dcs-Ins117, and a PCR-based method for identifying this structure was developed. The hospital-acquired isolates were found to contain eight different mecA downstream regions, three of which were novel. The Minimum SNPs computer software program was used to mine the S. aureus MLST database, and the arcC 272G polymorph was identified as 82% discriminatory for ST-30. A real-time PCR assay was developed to interrogate this SNP. We found that the assay for the truncated mecA downstream region in combination with the interrogation of arcC position 272 provided an unambiguous identification of WSPP isolates
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