Amplitude modulated flow analysis for speciation : Proof of concept by quantification of Fe2+ and Fe3+ ions

We propose a novel concept of flow-based analysis for spectrophotometric speciation based on flow rate modulation and fast Fourier transform (FFT). A redox reagent solution's and a sample solution's flow rates are varied by sinusoidal control signals with periods of T and 0.5T, respectively. Both solutions are merged with a color reagent, while the total flow rate is held constant. Downstream, the absorbance of the mixed solution is measured and acquired as the detector output voltage (Vd). The Vd is analyzed by FFT with the window's time length of T. One species that directly reacts with the color reagent contributes only to the amplitude (A2) of the second harmonic wave component in Vd. The other species that needs the redox conversion before the coloration contributes to the amplitude (A1) of the fundamental wave component, in addition to A2. The former species+' concentration can be estimated from A2 by taking the latter's contribution to A2 into account. The latter species’ concentration can be determined only from A1. The proposed concept was demonstrated by applying it to the speciation of Fe2+ and Fe3+ by an o-phenanthroline spectrophotometry, where Fe3+ was reduced to Fe2+ by L-ascorbic acid before the coloration

Global Spread of Multiple Aminoglycoside Resistance Genes

Emergence of the newly identified 16S rRNA methylases RmtA, RmtB, and ArmA in pathogenic gram-negative bacilli has been a growing concern. ArmA, which had been identified exclusively in Europe, was also found in several gram-negative pathogenic bacilli isolated in Japan, suggesting global dissemination of hazardous multiple aminoglycoside resistance genes

Cross sections for nuclide production in proton- and deuteron-induced reactions on 93

Isotopic production cross sections were measured for proton- and deuteron-induced reactions on 93Nb by means of the inverse kinematics method at RIKEN Radioactive Isotope Beam Factory. The measured production cross sections of residual nuclei in the reaction 93Nb + p at 113 MeV/u were compared with previous data measured by the conventional activation method in the proton energy range between 46 and 249 MeV. The present inverse kinematics data of four reaction products (90Mo, 90Nb, 88Y, and 86Y) were in good agreement with the data of activation measurement. Also, the model calculations with PHITS describing the intra-nuclear cascade and evaporation processes generally well reproduced the measured isotopic production cross sections

A New TEM-Derived Extended-Spectrum β-Lactamase (TEM-91) with an R164C Substitution at the Ω-Loop Confers Ceftazidime Resistance

A new plasmid-mediated TEM-derived extended-spectrum β-lactamase, TEM-91, was identified in a ceftazidime-resistant (MIC, >128 μg per ml) Escherichia coli strain isolated in 1996 in Japan. TEM-91 has three amino acid substitutions, R164C, M184T, and E240K, compared with TEM-1 penicillinase. The isoelectric point (pI), K(m), and k(cat) of TEM-91 for ceftazidime were 5.7, 179 μM, and 29.0 s(−1), respectively. The K(i) of clavulanic acid for ceftazidime hydrolysis was 30.3 nM

Characterization of a Novel Plasmid-Mediated Cephalosporinase (CMY-9) and Its Genetic Environment in an Escherichia coli Clinical Isolate

An Escherichia coli strain, HKYM68, which showed resistance to broad-spectrum cephalosporins was isolated from a sputum specimen in Japan. The high-level resistance of the strain to ceftazidime, cefpirome, and moxalactam was carried by a self-transferable plasmid. The β-lactamase gene responsible for the resistance was cloned and sequenced. The deduced amino acid sequence of this gene product, CMY-9, had a single amino acid substitution (E85D), the residue reported to be part of the recognition site for the R1 side chain of β-lactams, compared with the amino acid sequence of CMY-8 and also had 78% identity with the amino acid sequence of CepH, a chromosomal cephalosporinase of Aeromonas hydrophila. A sul1-type class 1 integron containing an aacA1-orfG gene cassette was identified upstream of bla(CMY-9) and ended with a truncated 3′ conserved segment. The following 2.1 kb was almost identical to the common region of integrons In6 and In7 and the integron of pSAL-1, except that orf513 encoding a putative transposase was identified instead of orf341 due to addition of a single nucleotide. bla(CMY-9) was closely located downstream of the end of the common region. These observations are indicative of the exogenous derivation of bla(CMY-9) from some environmental microorganisms such as aeromonads

PCR Typing of Genetic Determinants for Metallo-β-Lactamases and Integrases Carried by Gram-Negative Bacteria Isolated in Japan, with Focus on the Class 3 Integron

From January 2001 to December 2002, 587 strains of gram-negative bacterial isolates demonstrating resistance to ceftazidime and a combination of sulbactam and cefoperazone were subjected to a disk diffusion screening test using sodium mercaptoacetic acid; 431 strains (73.4%) appeared to produce metallo-β-lactamase (MBL). Of these 431 strains, 357 were found by PCR to carry genes for IMP-1 type MBL (bla(IMP-1)), while only 7 and 67 strains carried the IMP-2 gene (bla(IMP-2)) and the VIM-2 gene (bla(VIM-2)), respectively. Neither VIM-1 nor SPM-1 type MBL genes were found among the strains tested. Of 431 strains, 427 carried the intI1 gene, and 4 strains carrying both the intI1 and intI3 genes were reidentified as Pseudomonas putida harboring bla(IMP-1). Of these four P. putida strains, three strains and one strain, respectively, were separately isolated from two hospitals located in the same prefecture, and the three strains showed very similar pulsed-field gel electrophoresis patterns. Of 357 bla(IMP-1) carriers, 116, 53, 51, 47, and 30 strains were identified as Pseudomonas aeruginosa, Alcaligenes xylosoxidans, P. putida/fluorescens, Serratia marcescens, and Acinetobacter baumannii, respectively. Four strains carrying bla(IMP-2) were reidentified as P. putida. Sixty-three P. aeruginosa strains and four P. putida strains carried bla(VIM-2). Of 427 intI1-positive strains, 180, 53, 51, 47, and 35 were identified as P. aeruginosa, A. xylosoxidans, P. putida/fluorescens, S. marcescens, and A. baumannii, respectively. In the present study, it was confirmed that strains carrying bla(IMP-1) with a class 1 integron are the most prevalent type in Japan, although several intI3 carriers have also been identified sporadically in this country