Dissemination of three coliphages in chicken’s organism

Fundação para a Ciência e a Tecnologia (FCT

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

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

Isolation of lytic phages for clinical antibiotic resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa is a relevant opportunist pathogen involved in noso-comial infections. P. aeruginosa uses an arsenal of virulence factors to cause serious infections and one of the most worrying characteristics of this bacte-rium is its low antibiotic susceptibility. The low susceptibility to antibiotics can be attributed to a concerted action of multidrug efflux pumps with chromo-somally-encoded antibiotic resistance genes and the low permeability of the bacterial cellular envelopes. Furthermore, P. aeruginosa can develop acquired resistance either by mutation in chromosomally-encoded genes or by the horizontal gene transfer of antibiotic resistance determinants. Today, prevention and control of bacterial resistance requires new antimicrobial agents, the prudent use of existing ones, new vaccines and enhanced public health efforts to reduce transmission of bacterial resistance. Bacteriophages and their lytic enzymes can be an alternative to antibiotherapy towards the reduction of P. aeruginosa, without causing elimination of beneficial microorganisms. In this work, 4 P. aeruginosa strains, namely ATCC, CECT 111, PAO1 were used to screen for phages present in hospital effluents. Overall, 17 different bacteriophages were isolated. These newly isolated phages were tested against 35 antibiotic multi-resistant clinical strains provided by the São Marcos hospital (Braga) and their lytic spectra studied. Most phages were well capable of infecting different isolates, however some phages had quite a narrow spectrum of activity. The best four phages were selected and characterized according to their structural proteins and one-step growth

Isolation of novel bacteriophages for the control of P. aeruginosa biofilms

Pseudomonas aeruginosa is one of the most common gram-negative bacterium involve in nosocomial infections and, worryingly, it frequently shows a low antibiotic susceptibility. Additionally, P. aeruginosa has an inapt ability to adhere to surfaces and form virulent biofilms which are particularly difficult to eradicate. In this way, there is a need to develop new antimicrobial agents as an alternative to antibiotherapy and bacteriophages (phages) appear as one attractive solution for this problem. This work describes the isolation and characterization of novel phages and their application for planktonic and biofilm cell control. 17 different phages were isolated from hospital effluents and were tested against 35 antibiotic multi-resistant clinical strains provided by the São Marcos Hospital (Braga). Four of these phages, showing broad lytic spectra, were selected and their efficacy against planktonic cells was studied. Despite the superior lytic spectra exhibited by the selected phages, two of them were not efficient against their hosts and therefore were not chosen for biofilm control experiments. Meanwhile, the other 2 phages (phages phiIBB-PAA2 and phiIBB-PAP21), well capable of causing a great biomass reduction of planktonic cells, were tested against 24 hours old biofilms using different multiplicities of infection (MOI). Both phages caused an approximately 2 log reduction of biofilm-cells, already after 2 hours and the reduction was further enhanced after 6 hours of biofilm treatment, independently of the MOI. The main dissimilarity between the two phage-host systems concerns the biofilm-cell resistance to the phages. In brief, biofilm-cells of P. aeruginosa PAO1, the host of phage phiIBB-PAP21, acquired resistance to the phage and consequently an increase on the amount of cells after 24 hours of infection was observed. On the other hand, phage phiIBB-PAA2 continued to destroy the biofilms of P. aeruginosa ATCC 10145 and there were no evidences of cells becoming resistant, even after 24 hours of infection. This work shows that the two selected phages are well capable of controlling biofilms; however short treatment prevents the emergence of phage resistant hosts

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

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