The Effect of Sub-MIC β-Lactam Antibiotic Exposure of Pseudomonas aeruginosa Strains from People with Cystic Fibrosis in a Desiccation Survival Model

Prior to modern typing methods, cross-infection of P. aeruginosa between people with cystic fibrosis (CF) was felt to be rare. Recently a number of studies have demonstrated the presence of clonal strains of P. aeruginosa infecting people with CF. The aim of this study was to determine whether strains of P. aeruginosa demonstrated differences in resistance to desiccation and whether preincubation in subminimum inhibitory concentrations (MICs) of β-lactam affected desiccation resistance. The experimental data were modelled to a first-order decay model and a Weibull decay model using least squares nonlinear regression. The Weibull model was the preferred model for the desiccation survival. The presence of a mucoid phenotype promoted desiccation survival. Preincubation with antibiotics did not have a consistent effect on the strains of P. aeruginosa. Meropenem reduced desiccation resistance, whereas ceftazidime had much less effect on the strains studied

Finite Element Analysis of the Magneto-mechanical Coupling Due to Punching Process in Electrical Steel Sheet

In this article, a finite element (FE) modeling of the punching effect on the magnetic properties of electrical steel sheet is carried out. For that, the modified anhysteretic Sablik model is applied together with the plastic strain distribution obtained from a punching process simulation performed using the software ABAQUS. First, a synchronous electrical machine is simulated including the effect of the punching process, and it shows the degradation of the magnetic flux density at the lamination edges and an increase of the iron losses. Then, results obtained from the magneto-mechanical simulation are investigated in terms of the method used to implement the plastic strain distribution in the FE computation. Two examples have been investigated: a square steel sheet and a tooth of an electrical machine.Peer reviewe

Determination of stress dependent magnetostriction from a macroscopic magneto-mechanical model and experimental magnetization curves

In this paper, we propose a method to identify the magnetostrictive behavior of electrical steel sheet submitted to a mechanical loading. The technique relies on the use of a magneto-mechanical model including the magnetostrictive phenomenon, namely the anhysteretic Jiles-Atherton-Sablik (JAS) model, and experimental macroscopic stress dependent magnetization curves. The method is illustrated with measured magnetization curves of a non-oriented (NO) electrical steel sheet under different stresses. Furthermore, the influence of a bi-axial mechanical loading on the magnetostrictive behavior is analyzed with the help of an equivalent stress.Peer reviewe

bla(IMP-9) and Its Association with Large Plasmids Carried by Pseudomonas aeruginosa Isolates from the People's Republic of China

A novel plasmid-mediated metallo-β-lactamase (IMP-9) is described in seven isolates of Pseudomonas aeruginosa from Guangzhou, China, isolated in 2000. The gene was carried on a large (∼450-kb) IncP-2 conjugative plasmid. This is the first report of carriage of bla(IMP) genes on such large plasmids

Discrimination of SHV β-Lactamase Genes by Restriction Site Insertion-PCR

Restriction site insertion-PCR (RSI-PCR) is a simple, rapid technique for detection of point mutations. This technique exploits primers with one to three base mismatches near the 3′ end to modulate a restriction site. We have developed this technique to identify described mutations of the bla(SHV) genes for differentiation of SHV variants that cannot be distinguished easily by other techniques. To validate this method, eight standard strains were used, each producing a different SHV β-lactamase: SHV-1, SHV-2, SHV-3, SHV-4, SHV-5, SHV-6, SHV-8, and SHV-18. Mismatch primers were designed to detect mutations affecting amino acids at positions 8 (SspI), 179 (HinfI), 205 (PstI), 238 (Gly→Ala) (BsrI), and 240 (NruI) of bla(SHV) genes. All amplimers of the bla(SHV) genes used in this study yielded the predicted restriction endonuclease digestion products. In addition, this study also makes theoretical identification of bla(SHV-6), bla(SHV-8), and 12 novel bla(SHV) variants using the PCR-restriction fragment length polymorphism (RFLP) technique possible. By using a combination of PCR-RFLP and RSI-PCR techniques, up to 27 SHV variants can now be distinguished rapidly and reliably. These simple techniques are readily applied to epidemiological studies of the SHV β-lactamases and may be extended to the characterisation of other resistance determinants