THE FORGOTTEN ORIGINS OF ANTIMICROBIAL RESISTANCE

The evolution and spread of resistance to antimicrobial drugs is currently viewed as a growing public concern, being ranked alongside other major threats such as climate change and terrorism. Interestingly, antimicrobial resistance is most often framed as a recent phenomenon, which results from the use and abuse of antibiotics in the clinic and husbandry. According to this view, the antimicrobial drugs used before the 1940s did not drive the emergence of resistance outside the laboratory and, therefore, antimicrobial resistance was not perceived as a clinical problem at the time. This dissertation challenges this view. By surveying major biomedical articles and textbooks on the treatment of syphilis with Salvarsan–one of the earliest antimicrobial drugs available in medicine–I show here that clinical antimicrobial resistance is older than we think, and that it motivated a reciprocal exchange of knowledge between the laboratory and the clinic, which have been claimed distant in the first decades of the 20th century. Importantly, the key primary sources used and analysed in this dissertation have hardly been cited by biomedical researchers and historians in their works on the history of antimicrobial resistance, despite being published in top-tier journals on syphilology and its treatment. This aspect begs the question: Why was the earlier history of drug resistance forgotten in these accounts? I argue that the historical amnesia about arsenic-resistant syphilis that I explore in this dissertation is consistent with what is known about the historical amnesia of biomedical knowledge more generally

Scalaroca stars: coupled scalar-Proca solitons

We construct and explore the physical properties of \textit{scalaroca stars}: spherically symmetric solitonic solutions made of a complex scalar field $\Phi$ and a complex Proca field $A^\mu$. We restrict our attention to configurations in which both fields are in the fundamental state and possess an equal mass, focusing on the cases when ($i$) the scalar and Proca fields are (non--linearly) super--imposed and do not interact with each other; and ($ii$) the scalar and Proca fields interact through the term $\alpha |\Phi| ^2 A^\mu A_\mu$. The solutions are found numerically for the non--interacting case ($\alpha=0$) as well as for both signs of the interaction coupling constant $\alpha$. While pure ($i.e.$ single--field) Proca/scalar boson stars are the most/least massive for weakly--interacting fields, one can obtain more massive solutions for a sufficiently strong interaction. Besides, in the latter case, solutions can be either in a synchronized state -- in which both fields have the same frequency -- or in a non--synchronized state. In addition, we observe that the coupling between the two fields allows solitonic solutions with a real scalar field. We further comment on the possibility of spontaneous scalarization and vectorization of the interacting solitonic solution.Comment: 21 pages, 13 figures, this project was started before the recently published work ArXiv:2304.0801

Effects of glazing and chitosan-based coating application on frozen salmon preservation during six-month storage in industrial freezing chambers

Freezing and glazing are techniques commonly used to reduce the incidence of fish deterioration processes. In order to find an alternative to complement freezing and replace water glazing, the present work aimed at evaluating the effect of water glazing and edible coatings of 0.5% w/v and 1.5% w/v chitosan on quality parameters of frozen fish. Both types of coatings - water glazing and chitosan coatings - were applied directly on frozen Atlantic salmon (Salmo salar) and stored for 9 months at -22 °C. Several parameters such as coating/glazing loss, weight loss, drip loss, Total Viable Counts (TVC), Total Volatile Basic-Nitrogen (TVB-N), K-value, pH and color coordinates L*a*b* were periodically evaluated in order to compare glazing with the chitosan-based coatings and uncoated control samples. Samples coated with 1.5% w/v chitosan performed better in maintaining the color of the salmon and controlling microbial contamination of frozen and thawed samples

Single-cell twitching chemotaxis in developing biofilms

Bacteria form surface-attached communities, known as biofilms, which are central to bacterial biology and how they affect us. Although surface-attached bacteria often experience strong chemical gradients, it remains unclear whether single cells can effectively perform chemotaxis on surfaces. Here we use microfluidic chemical gradients and massively parallel automated tracking to study the behavior of the pathogen Pseudomonas aeruginosa during early biofilm development. We show that individual cells can efficiently move toward chemoattractants using pili-based “twitching” motility and the Chp chemosensory system. Moreover, we discovered the behavioral mechanism underlying this surface chemotaxis: Cells reverse direction more frequently when moving away from chemoattractant sources. These corrective maneuvers are triggered rapidly, typically before a wayward cell has ventured a fraction of a micron. Our work shows that single bacteria can direct their motion with submicron precision and reveals the hidden potential for chemotaxis within bacterial biofilms

Alternative regimens for prostate cancer treatment using radiation therapy

Purpose/Objective: The purpose of this work was to determine biologically equivalent alternative regimens for the treatment of prostate cancer using External Beam Radiotherapy (EBRT) and Low Dose-Rate Brachytherapy (LDRBT) with 125I implants and to evaluate the sensitivity of these regimens to different sets of radiobiological parameters of the Linear-Quadratic (LQ) model

Two-dimensional open microfluidic devices by tuning the wettability on patterned superhydrophobic polymeric surface

We present a simple and economical method to produce a potential open microfluidic polymeric device. Biomimetic superhydrophobic surfaces were prepared on polystyrene using a phase separation methodology. Patterned two-dimensional channels were imprinted on the superhydrophobic substrates by exposing the surface to plasma or UV–ozone radiation. The wettability of the channels could be precisely controlled between the superhydrophobic and superhydrophilic states by changing the exposure time. The ability of superhydrophilic paths to drive liquid flows in a horizontal position was found to be significantly higher than for the case of hydrophilic paths patterned onto smooth surfaces.(undefined

Recent advances on open fluidic systems for biomedical applications: A review

Microfluidics has become an important tool to engineer microenvironments with high precision, comprising devices and methods for controlling and manipulating fluids at the submillimeter scale. A specific branch of microfluidics comprises open fluidic systems, which is mainly characterized by displaying a higher air/liquid interface when compared with traditional closed-channel setups. The use of open channel systems has enabled the design of singular architectures in devices that are simple to fabricate and to clean. Enhanced functionality and accessibility for liquid handling are additional advantages inputted to technologies based on open fluidics. While benchmarked against closed fluidics approaches, the use of directly accessible channels decreases the risk of clogging and bubble-driven flow perturbation. In this review, we discuss the advantages of open fluidics systems when compared to their closed fluidics counterparts. Platforms are analyzed in two separated groups based on different confinement principles: wall-based physical confinement and wettability-contrast confinement. The physical confinement group comprises both open and traditional microfluidics; examples based on open channels with rectangular and triangular cross-section, suspended microfluidics, and the use of narrow edge of a solid surface for fluid confinement are addressed. The second group covers (super)hydrophilic/(super)hydrophobic patterned surfaces, and examples based on polymer-, textile- and paper-based microfluidic devices are explored. The technologies described in this review are critically discussed concerning devices' performance and versatility, manufacturing techniques and fluid transport/manipulation methods. A gather-up of recent biomedical applications of open fluidics devices is also presented.European Research Council grant agreement ERC-2012-ADG 20120216-321266 for project ComplexiTE and ERC-2014-ADG-669858 for project “ATLAS”. N. M. Oliveira acknowledges the financial support from Portuguese Foundation for Science and Technology − FCT (Grant SFRH/BD/73172/2010), from the financial program POPH/FSE from QREN. The work was developed within the scope of the project CICECO Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013). Sara Vilabril acknowledges the financial support from national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreementinfo:eu-repo/semantics/publishedVersio