A total of 149 porcine Staphylococcus isolates with florfenicol MICs of >16 g/ml were screened for the presence of the multiresistance gene cfr, its location on plasmids, and its genetic environment. In total, 125 isolates carried either cfr (16 isolates), fexA (92 isolates), or both genes (17 isolates). The 33 cfr-carrying staphylococci, which included isolates of the species Staphylococcus cohnii, S. arlettae, and S. saprophyticus in which the cfr gene has not been described before, exhibited a wide variety of SmaI pulsed-field gel electrophoresis patterns. In 18 cases, the cfr gene was located on plasmids. Four different types of cfr-carrying plasmids-pSS-01 (n ؍ 2; 40 kb), pSS-02 (n ؍ 3; 35.4 kb), pSS-03 (n ؍ 10; 7.1 kb), and pBS-01 (n ؍ 3; 16.4 kb)-were differentiated on the basis of their sizes, restriction patterns, and additional resistance genes. Sequence analysis revealed that in plasmid pSS-01, the cfr gene was flanked in the upstream part by a complete aacA-aphD-carrying Tn4001-like transposon and in the downstream part by a complete fexA-carrying transposon Tn558. In plasmid pSS-02, an insertion sequence IS21-558 and the cfr gene were integrated into transposon Tn558 and thereby truncated the tnpA and tnpB genes. The smallest cfr-carrying plasmid pSS-03 carried the macrolide-lincosamide-streptogramin B resistance gene erm(C). Plasmid pBS-01, previously described in Bacillus spp., harbored a Tn917-like transposon, including the macrolide-lincosamide-streptogramin B resistance gene erm(B) in the cfr downstream region. Plasmids, which in part carry additional resistance genes, seem to play an important role in the dissemination of the gene cfr among porcine staphylococci.
We describe a preconcentration device that may be suitable for quantitative analysis of trace volatile ketones and aldehydes in ambient air as well as in human breath. The approach is based on microreactor chips fabricated from silicon wafers. The microreactors have thousands of micropillars in microfluidic channels for uniformly distributing a gaseous sample flowing through the chips. The surfaces of the micropillars are functionalized with a quaternary ammonium aminooxy salt, [2-(aminooxy)ethyl]-N,N,N-trimethylammonium iodide (ATM), for trapping trace ketones and aldehydes by means of oximation reactions. ATM adducts and unreacted ATM are eluted from the microreactor with less than 40 μL of methanol and directly analyzed by nanospray Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS). Ketones and aldehydes at levels of 1 ppbv have been detected using this microreactor and FTICR-MS system.
We report a fabricated microreactor with thousands of micropillars in channels. Each micropillar surface is chemically functionalized to selectively preconcentrate gaseous ketones and aldehydes of exhaled breath and to enhance ultra-trace, rapid analysis by direct-infusion Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometry (MS). The micropillar reactive coating contains the quaternary ammonium aminooxy salt 2-(aminooxy)ethyl-N,N,N-trimethylammonium iodide (ATM) for capturing trace carbonyl VOCs by means of an oximation reaction. We demonstrate the utility of this approach for detection of C(1) to C(12) aldehydes and ketones in exhaled breath, but the approach is applicable to any gaseous sample.
Transformer coupled plasma etching of 3C-SiC films using fluorinated chemistry for microelectromechanical systems applications Growth of cubic SiC thin films on Si(001) by high vacuum chemical vapor deposition using 1,3-disilabutane and an investigation of the effect of deposition pressure Residual stress and texture in poly-SiC films grown by low-pressure organometallic chemical-vapor deposition
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