In this study, we describe a multiplex PCR to detect a AGC3ACC (serine to threonine) mutation in the katG gene and a ؊15 C-to-T substitution (inhA C؊15T Currently, throughout the world, isoniazid (INH) and rifampin (RIF) together represent the backbone of short-course chemotherapy for Mycobacterium tuberculosis infections. The number of multidrug-resistant strains of M. tuberculosis, defined as resistant to INH and RIF, has been increasing over the years, and several outbreaks have been reported (5, 9, 24). The development of resistance to these two drugs reduces the efficacy of standard antituberculosis (anti-TB) treatment to 77%. It is very important, therefore, to identify these strains as soon as possible to allow for adjustments in treatment and to minimize the transmission of drug-resistant strains. Phenotypic drug susceptibility testing by conventional methods on solid media (6, 8) requires 10 to 30 days after the primary culture has been isolated. This time can be reduced by the use of rapid methods such as BACTEC, which requires 5 to 10 days.)Resistance to RIF has been shown to be caused by an alteration of the ␤ subunit of RNA polymerase, which is encoded by the rpoB gene. More than 95% of RIF-resistant strains are associated with mutations within an 81-bp region of the rpoB gene (encoding the RNA polymerase ␤ subunit). Specific mutations, insertions, and deletions have been described in several countries by several authors, and this 81-bp region has been termed the rifampin resistance determinant region (7,14,20,26,27,30). Numerous methods exist to detect resistance to rifampin (10,12,18,23).In contrast, resistance to INH is more complicated, as mutations in several genes can lead to drug resistance. For most INH-resistant strains, mutations have been found in two genes, i.e., the katG gene, encoding catalase-peroxidase (31), and the mabA-inhA regulon (4), encoding a target of activated prodrug, enoyl-acyl carrier protein reductase (1-3, 11, 13, 15, 17, 21, 27). For some other INH-resistant strains, however, mutations in the ahpC promoter region (located in the 105-bp oxyR-ahpC intergenic region) or within the ␤-ketocyl acyl carrier protein synthase gene kasA have also been reported (19,25). Most studies have examined the mutations present in these genes by DNA sequencing or analyses of a portion of the katG gene after PCR amplification and digestion with the restriction enzyme MspI or SatI (2, 3, 17).Molecular methods have been developed to detect resistance to INH and RIF as an alternative to conventional tests because of their ability to provide results rapidly. Upon the elucidation of the genes involved in resistance to RIF and INH, several studies describing various PCR-based molecular genetic techniques for the detection of resistance were published (12).In the present study, we report a simple, rapid, and inexpensive assay based on allele-specific PCR methodology targeting an AGC3ACC mutation in the katG gene and an inhA CϪ15T mutation in the regulatory region of the mabA-inhA operon to detect...

Spray drying and freeze drying are well established granulation processes for submicron and micron sized particles. In recent years, granulation of nanoparticle suspensions is receiving increased interest for the production of nanostructured materials.In this work the spray drying and freeze drying of different nanosized ceramic materials and the physicochemical characteristics of the obtained granules (size distribution, morphology, surface area, porosity, and flow parameters) are studied. Commercial colloidal suspensions of alumina and titania were studied, as well as a mixture of both with a relative weight ratio of 87/13. On one hand, the influence of temperature, pressure and nozzle diameter on the morphology and characteristics of spray dried granules are studied. On the other hand, the effect of air pressure and nozzle diameter on the morphology and properties of freeze dried granules was evaluated. The influence of solids loading of the starting suspensions has been also studied.It has been demonstrated that these processing parameters have practically no influence on the granules morphology and properties, and the only parameter determining the granules characteristics is the solids content of the suspensions, either in the spraying or in the freezing process. Spray drying leads to a monomodal distribution with higher granule size, while freeze drying produces more porous granules, with a bimodal intragranular distribution. The flowability of spray-dried powder is better than that of the freeze-dried powder. As a result, the characteristics of the spray-dried powder suit better the requirements of a feedstock targeted to obtain coatings by plasma thermal spraying whereas freeze drying can produce high porosity, softer granules.

No abstract

Atmospheric plasma spraying (APS) is an interesting technique to obtain nanostructured coatings due to its versatility, simplicity and relatively low cost. However, nanometric powders can not be fed into the plume using conventional feeding systems, due to their low mass and poor flowability, and must be adequately reconstituted into sprayable micrometric agglomerates.In this work, Al 2 O 3 -13wt%TiO 2 nanostructured and submicron-nanostructured powders were deposited using APS. The feedstocks were obtained by spray drying from two starting suspensions, prepared by mixing two commercial nanosuspensions of Al 2 O 3 and TiO 2 , or by adding nanosized TiO 2 and submicron-sized Al 2 O 3 powders to water. The spray-dried granules were heat-treated to reduce their porosity and the resultant powders were fully characterised.Optimisation of the deposition conditions enabled the reconstituted powders to be successfully deposited, yielding coatings that were well bonded to the substrate. The coating microstructure, characterised by SEM, was formed by semi-molten feedstock agglomerates surrounded by fully molten particles that act as a binder.Moreover, microhardness, adhesion, and tribological behaviour were determined, and the impact of the granule characteristics on these properties was studied. It was found that changing the feedstock characteristics allows to control the coating quality and properties.2