Dissemination of three coliphages in chicken’s organism

Fundação para a Ciência e a Tecnologia (FCT

Combined antibiotic-phage therapies to control Pseudomonas aeruginosa biofilms

Pseudomonas aeruginosa is responsible for 65% of mortality in hospitals all over the world. Its prevalence is attributed to factors such as: intrinsic resistance determined by virulence factors; acquired resistance mechanisms that lead to a low susceptibility to antimicrobial agents; and ability to attach to any natural and artificial surfaces and form biofilms. The emergence of new strategies to control P. aeruginosa biofilms is becoming more evident due to their tolerance to traditional treatments and bacteriophages have been recognized as an attractive alternative for this problem. Nevertheless, despite the potential of phages as antimicrobial agents, it is well known that bacteria can quickly adapt and create new survival strategies and the emergence of phage-resistant phenotypes is inevitable. Thus, the combination of phage and antibiotic therapies could have potentially more benefits than just using phages and antibiotics alone. This work describes the combinatory treatment using P. aeruginosa phages and antibiotics (amikacin, ciprofloxacin, piperacillin and tetracycline) against biofilms. The efficacy of phages and antibiotics were evaluated by the enumeration of viable cells and the determination of biofilm biomass. All antibiotics tested showed little efficacy against biofilms which were also very tolerant to phage infection, partially due to the fast emergence of resistant phenotypes with LPS mutations. However, the association of phage and ciprofloxacin caused a 100% biofilm removal. Synergy was observed with a combined phage-ciprofloxacin treatment, and overall an additive effect was seen with piperacillin and tetracyclin. Antagonism was observed with amikacin. Nevertheless, all antibiotic-phage combined treatments caused the disruption of the biofilm matrix. The effectiveness of combined treatments with phages and antibiotics can be due to several factors, namely high burst sizes in cells exposed to antibiotics (ex. piperacillin), lower MIC values and altered surface charges of phage resistant phenotypes and disruption of the biofilm matrix induced by some of the phages which can enhance the antibiotic penetration

In vivo toxicity study of phage lysate in chickens

1. Bacteriophage (phage) crude lysate of Gram-negative bacteria often contains bacterial debris, including lipopolysaccharides found in the outer membrane of the cell wall, which are potentially toxic. 2. In this study, an in vivo evaluation of the toxicity of a suspension of three phages to control pathogenic Escherichia coli strains in poultry was performed. 3. Eighteen commercial layers, 7 weeks old, were intramuscularly injected with phage lysate (8.21x10 4 Endotoxin Units/dose). The control group was injected with sterile Luria Bertani (LB) broth. 4. Bird prostration and decrease in body weight gain and water intake per gram of body weight were observed only on the day of the inoculation in the challenged group. Over the following 6 d, no differences were observed in the chickens’ activity. 5. These results support the view that phage crude lysate carrying endotoxins are not toxic for chickens.Fundação para a Ciência e a Tecnologia (FCT

The role of hydrophobicity in bacterial adhesion

In biological systems, hydrophobic interactions are usually considered to be the strongest of all long-range non-covalent interactions. Considering hydrophobicity as the energy of interaction, ΔGiwi, between two entities (i) immersed in water (w): then a positive value means that i is hydrophilic, and when ΔGiwi has a negative value, i is hydrophobic. In other words, an increase in ΔGiwi means a decrease in hydrophobicity. The above concept was used in the interpretation of various adhesion experiments: (I) adhesion of a denitrifying strain (Alcaligenes denitrificans) to polymeric surfaces; (II) adhesion of an anaerobic consortium to porous microcarriers; (IV) adhesion of Staphylococcus epidermidis to polymeric materials, used in medical indwelling devices. In all the mentioned studies a linear correlation was obtained between the degree of hydrophobicity of the supporting surfaces and the number of adhered cells

Uso de RMN no Estado Estacionário para Aumento de Sensibilidade de Análises Químicas.

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Aplicações da espectroscopia de RMN (CWFP) na medida de umidade em sementes e grãos.

Neste trabalho demonstramos as vantagens e desvantagens de se usar a técnica de CWFP para medidas de óleo e umidade em sementes, em relação as técnicas normais de RMN com o uso do FID e eco.bitstream/CNPDIA/8115/1/CiT14_2002.pd

Formation and Stability of Synaptic Receptor Domains

Neurotransmitter receptor molecules, concentrated in postsynaptic domains along with scaffold and a number of other molecules, are key regulators of signal transmission across synapses. Employing experiment and theory, we develop a quantitative description of synaptic receptor domains in terms of a reaction-diffusion model. We show that interactions between only receptor and scaffold molecules, together with the rapid diffusion of receptors on the cell membrane, are sufficient for the formation and stable characteristic size of synaptic receptor domains. Our work reconciles long-term stability of synaptic receptor domains with rapid turnover and diffusion of individual receptors.Comment: 5 pages, 3 figures, Supplementary Materia

Revisiting phage therapy: new applications for old resources

The success of phage therapy is dependent on the development of strategies able to overcome the limitations of bacteriophages as therapeutic agents, the creation of an adequate regulatory framework, the implementation of safety protocols, and the acceptance by the general public. Many approaches have been proposed to circumvent phages intrinsic limitations but none have proved to be completely satisfactory. In this review we present the major hurdles of phage therapy and the solutions proposed to circumvent them. A thorough discussion on the advantages and drawbacks of these solutions is provided and special attention is given to genetic modification of phages as an achievable strategy to shape bacteriophages to exhibit desirable biological properties.The authors thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013 and the Project 'BioHealth - Biotechnology and Bioengineering approaches to improve health quality, Ref. NORTE-07-0124-FEDER-000027' cofunded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, and FEDER. F.L.N. also acknowledges the FCT for grant SFRH/BD/86462/2012