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[Abstract] The discovery of new antibiotics that are effective against Acinetobacter baumannii and Enterobacteralesis a research priority. Several essential oils (EOs) have displayed some antimicrobial activity and could potentially act as antibiotic adjuvants. Research in this area aims to develop new therapeutic alternatives to treat infections caused by these pathogens. MICs of different EOs were determined against A. baumannii and Klebsiella pneumoniae. Combined disk diffusion tests and checkerboard assays were used to study the synergy between the EOs and antibiotics. The fractional inhibitory concentration index (FICindex) was calculated in order to categorize the interaction. Time-kill assays were also performed. The EOs that displayed the highest levels of antimicrobial activity were clove (Syzygium aromaticum L.) and thyme (Thymus zygis L.). Combined disk diffusion tests and checkerboard assays revealed synergy between these EOs and colistin. Addition of either clove or thyme EO decreased the MIC of colistin by 8- to 64-fold and 8- to 128-fold in the colistin-resistant A. baumannii and K. pneumoniae strains, respectively (FICindex ≤ 0.5, synergy). MICs were also reduced in the colistin-susceptible strains. Time-kill assays also indicated the strong activity of the combined therapy. In summary, the use of clove or thyme EO in combination with colistin could improve the efficacy of the antibiotic and significantly reduce the concentrations needed to inhibit growth of A. baumannii and K. pneumoniae.

[Abstract] Acinetobacter baumannii is currently considered one of themost problematic nosocomial microorganisms. In the present work the hisF gene from the ATCC 17978 strain and the AbH12O-A2 clinical isolate of A. baumannii was found over-expressed during the course of murine pneumonia infections. The study demonstrated that the A. baumannii ATCC 17978 mutant strain lacking the hisF gene induces a sub-lethal pneumonia infection in mice, while the complemented mutant strain increased its virulence. This histidine auxotroph mutant showed an increase on IL-6 secretion and leukocytes recruitment during infections. Furthermore, data revealed that the hisF gene, implicated in the innate immunity and inflammation, is involved in virulence during a pneumonia infection, which may partly explain the ability of this strain to persist in the lung. We suggest that HisF, essential for full virulence in this pathogen, should be considered a potential target for developing new antimicrobial therapies against A. baumannii.

[Abstract] We report here the draft genome sequences of Klebsiella pneumoniae strains Kp1803 and Kp3380 isolated during a large outbreak at A Coruña Hospital in Spain. The final genome assemblies for Kp1803 and Kp3380 comprise approximately 6.6 and 6.1 Mb, respectively, and both strains have G+C contents of 57.2%.

[Resumo] Acinetobacter baumannii é un patóxeno oportunista que xurdiu nos últimos anos como un dos microorganismos máis perigosos dentro do ambiente hospitalario. Na presente tese doutoral caracterizáronse dous novos factores de virulencia que poderían explicar parcialmente a habilidade que ten A. baumannii para causar unha infección. O xene LH92_11085 de A. baumannii MAR002, implicado na formación dun pilus tipo chaperona- usher, atopouse sobreexpresado en células do biofilm en comparación con células planctónicas. A inactivación deste xene resultou nunha redución na capacidade da cepa de formar biofilm e de adherirse a células epiteliais e nun descenso na virulencia. O xene A1S_0242 (feoA) da cepa A. baumannii ATCC 17978, que está implicado na captación de ferro e que se atopou sobreexpresado durante un proceso de pneumonía, xoga un papel na adhesión, na formación de biofilm, na resistencia ó estrés oxidativo e na virulencia in vivo. Todos os resultados obtidos durante esta tese doutoral demostraron a contribución destes xenes na patoxénese de A. baumannii., [Resumen] Acinetobacter baumannii es un patógeno oportunista que ha emergido en los últimos años como uno de los microorganismos más peligrosos dentro del ambiente hospitalario. En la presente tesis doctoral se caracterizaron dos nuevos factores de virulencia que podrían explicar parcialmente la habilidad que tiene A. baumannii para causar una infección. El gen LH92_11085 de A. baumannii MAR002, implicado en la formación de un pilus tipo chaperona-usher, se encontró sobreexpresado en células del biofilm en comparación con células planctónicas. La inactivación de este gen resultó en una reducción en la capacidad de la cepa de formar biofilm y de adherirse a células epiteliales y un descenso en la virulencia. El gen A1S_0242 (feoA) de la cepa A. baumannii ATCC 17978, que está implicado en la captación de hierro y que se encontró sobreexpresado durante un proceso de neumonía, juega un papel en la adhesión, la formación de biofilm, la resistencia al estrés oxidativo y en la virulencia in vivo. Todos los resultados obtenidos durante esta tesis doctoral demostraron la contribución de estos genes a la patogénesis de A. baumannii., [Abstract] Acinetobacter baumannii is an opportunist pathogen that has emerged in the last years as one of the most dangerous microorganisms living in hospital environments. In the present work two new virulence factors, that could partially explain the ability of A. baumannii to cause an infection, have been characterized. The LH92_11085 gene of the A. baumannii MAR002 strain, involved in the formation of a chaperone-usher pilus system, was found as over-expressed in biofilm cells compared to planktonic cells. The inactivation of this gene resulted in a reduction in the capacity of the MAR002 strain to form biofilm and to adhere to human epithelial cells and in a decrease in virulence. The A1S_0242 gene (feoA) from the A. baumannii ATCC 17978 strain, which is involved in iron uptake and that was found as over-expressed during the course of a pneumonia infection, plays a role in adhesion, biofilm formation, resistance to oxidative stress and in virulence. Data obtained in this work demostrate the contribution of both genes to the pathogenesis of A. baumannii.

Genetic and functional studies showed that some components of the Acinetobacter baumannii ATCC 17978 A1S_0112-A1S_0119 gene cluster are critical for biofilm biogenesis and surface motility. Recently, our group has shown that the A1S_0114 gene was involved in biofilm formation, a process related with pathogenesis. Confirming our previous results, microscopy images revealed that the ATCC 17978 10114 derivative lacking this gene was unable to form a mature biofilm structure. Therefore, other bacterial phenotypes were analyzed to determine the role of this gene in the pathogenicity of A. baumannii ATCC 17978. The interaction of the ATCC 17978 parental strain and the 10114 mutant with A549 human alveolar epithelial cells was quantified revealing that the A1S_0114 gene was necessary for proper attachment to A549 cells. This dependency correlates with the negative effect of the A1S_0114 deletion on the expression of genes coding for surface proteins and pili-assembly systems, which are known to play a role in adhesion. Three different experimental animal models, including vertebrate and invertebrate hosts, confirmed the role of the A1S_0114 gene in virulence. All of the experimental infection assays indicated that the virulence of the ATCC 17978 was significantly reduced when this gene was inactivated. Finally, we discovered that the A1S_0114 gene was involved in the production of a small lipopeptide-like compound herein referred to as acinetin 505 (Ac-505). Ac-505 was isolated from ATCC 17978 spent media and its chemical structure was interpreted by mass spectrometry. Overall, our observations provide novel information on the role of the A1S_0114 gene in A. baumannii’s pathobiology and lay the foundation for future work to determine the mechanisms by which Ac-505, or possibly an Ac-505 precursor, could execute critical functions as a secondary metabolite

Many strains of Acinetobacter baumannii have been described as being able to form biofilm. Small non-coding RNAs (sRNAs) control gene expression in many regulatory circuits in bacteria. The aim of the present work was to provide a global description of the sRNAs produced both by planktonic and biofilm-associated (sessile) cells of A. baumannii ATCC 17978, and to compare the corresponding gene expression profiles to identify sRNAs molecules associated to biofilm formation and virulence. sRNA was extracted from both planktonic and sessile cells and reverse transcribed. cDNA was subjected to 454- pyrosequencing using the GS-FLX Titanium chemistry. The global analysis of the small RNA transcriptome revealed different sRNA expression patterns in planktonic and biofilm associated cells, with some of the transcripts only expressed or repressed in sessile bacteria. A total of 255 sRNAs were detected, with 185 of them differentially expressed in the different types of cells. A total of 9 sRNAs were expressed only in biofilm cells, while the expression of other 21 coding regions were repressed only in biofilm cells. Strikingly, the expression level of the sRNA 13573 was 120 times higher in biofilms than in planktonic cells, an observation that prompted us to further investigate the biological role of this noncoding transcript. Analyses of an isogenic mutant and over-expressing strains revealed that the sRNA 13573 gene is involved in biofilm formation and attachment to A549 human alveolar epithelial cells. The present work serves as a basis for future studies examining the complex regulatory network that regulate biofilm biogenesis and attachment to eukaryotic cells in A. baumannii ATCC 17978.

Acinetobacter baumannii is a nosocomial pathogen that has a considerable ability to survive in the hospital environment partly due to its capacity to form biofilms. The first step in the process of establishing an infection is adherence of the bacteria to target cells. Chaperone-usher pili assembly systems are involved in pilus biogenesis pathways that play an important role in adhesion to host cells and tissues as well as medically relevant surfaces. After screening a collection of strains, a biofilm hyper-producing A. baumannii strain (MAR002) was selected to describe potential targets involved in pathogenicity. MAR002 showed a remarkable ability to form biofilm and attach to A549 human alveolar epithelial cells. Analysis of MAR002 using transmission electron microscopy (TEM) showed a significant presence of pili on the bacterial surface. Putative protein-coding genes involved in pili formation were identified based on the newly sequenced genome of MAR002 strain (JRHB01000001/2 or NZ_JRHB01000001/2). As assessed by qRT-PCR, the gene LH92_11085, belonging to the operon LH92_11070-11085, is overexpressed (ca. 25-fold more) in biofilm-associated cells compared to exponential planktonic cells. In the present work we investigate the role of this gene on the MAR002 biofilm phenotype. Scanning electron microscopy (SEM) and biofilm assays showed that inactivation of LH92_11085 gene significantly reduced bacterial attachment to A549 cells and biofilm formation on plastic, respectively. TEM analysis of the LH92_11085 mutant showed the absence of long pili formations normally present in the wild-type. These observations indicate the potential role this LH92_11085 gene could play in the pathobiology of A baumannii.

A novel absorbing composite based on MoSi-SiN has been investigated to be used in high temperature solar selective coating applications. Simulation of the reflectance from the complex dielectric permittivity of the components has allowed the optimization of its optical characteristics. The sputtering deposited whole multilayer stacks, formed by a metallic infrared reflector, a double absorber composite and an antireflective layer, show optical performances as good as those obtained from similar composites such as Mo-SiN but with improved stability in moderate vacuum at temperatures up to 600°C.

Data of optical performance, thermal stability and ageing are given for solar selective coatings (SSC) based on a novel MoSi2–Si3N4 absorbing composite. SSC have been prepared as multilayer stacks formed by silver as metallic infrared reflector, a double layer composite and an antireflective layer (doi: 10.1016/j.solmat.2016.04.001 [1]). Spectroscopic reflectance data corresponding to the optical performance of samples after moderate vacuum annealing at temperatures up to 600 °C and after ageing test of more than 200 h with several heating–cooling cycles are shown here.

Acinetobacter baumannii has emerged as a dangerous opportunistic pathogen, with many strains able to form biofilms and thus cause persistent infections. The aim of the present study was to use high-throughput sequencing techniques to establish complete transcriptome profiles of planktonic (free-living) and sessile (biofilm) forms of A. ATCC 17978 and thereby identify differences in their gene expression patterns. Collections of mRNA from planktonic (both exponential and stationary phase cultures) and sessile (biofilm) cells were sequenced. Six mRNA libraries were prepared following the mRNA-Seq protocols from Illumina. Reads were obtained in a HiScanSQ platform and mapped against the complete genome to describe the complete mRNA transcriptomes of planktonic and sessile cells. The results showed that the gene expression pattern of A. baumannii biofilm cells was distinct from that of planktonic cells, including 1621 genes over-expressed in biofilms relative to stationary phase cells and 55 genes expressed only in biofilms. These differences suggested important changes in amino acid and fatty acid metabolism, motility, active transport, DNA-methylation, iron acquisition, transcriptional regulation, and quorum sensing, among other processes. Disruption or deletion of five of these genes caused a significant decrease in biofilm formation ability in the corresponding mutant strains. Among the genes over-expressed in biofilm cells were those in an operon involved in quorum sensing. One of them, encoding an acyl carrier protein, was shown to be involved in biofilm formation as demonstrated by the significant decrease in biofilm formation by the corresponding knockout strain. The present work serves as a basis for future studies examining the complex network systems that regulate bacterial biofilm formation and maintenance. © 2013 Rumbo-Feal et al.

A complete experimental study of temperature dependence of the total spectral emissivity has been performed, for the first time, for absorber-reflector selective coatings used in concentrated solar power (CSP) systems for energy harvesting. The coating consist of double cermet layers of silicon oxide with different amounts of molybdenum over a silver infrared mirror layer. The experimental measurements were carried out by a high accurate radiometer (HAIRL) with controlled atmosphere in the mid-infrared and for temperatures between 150 and 600 C. The spectral emissivity is nearly constant in this temperature range. Therefore, the temperature dependence of the total emissivity is given by Planck function. These results were compared with those obtained with the usual calculus using room temperature reflectance spectrum. Finally, the performance of the coating was analyzed by comparison of coated respect to non-coated stainless steel.