Pseudomonas aeruginosa can be detected in a polymicrobial competition model using impedance spectroscopy with a novel biosensor

Electrochemical Impedance Spectroscopy (EIS) is a powerful technique that can be used to elicit information about an electrode interface. In this article, we highlight six principal processes by which the presence of microorganisms can affect impedance and show how one of these - the production of electroactive metabolites - changes the impedance signature of culture media containing Pseudomonas aeruginosa. EIS, was used in conjunction with a low cost screen printed carbon sensor to detect the presence of P. aeruginosa when grown in isolation or as part of a polymicrobial infection with Staphylococcus aureus. By comparing the electrode to a starting measurement, we were able to identify an impedance signature characteristic of P. aeruginosa. Furthermore, we are able to show that one of the changes in the impedance signature is due to pyocyanin and associated phenazine compounds. The findings of this study indicate that it might be possible to develop a low cost sensor for the detection of P. aeruginosa in important point of care diagnostic applications. In particular, we suggest that a development of the device described here could be used in a polymicrobial clinical sample such as sputum from a CF patient to detect P. aeruginosa

The role of causal criteria in causal inferences: Bradford Hill's "aspects of association"

As noted by Wesley Salmon and many others, causal concepts are ubiquitous in every branch of theoretical science, in the practical disciplines and in everyday life. In the theoretical and practical sciences especially, people often base claims about causal relations on applications of statistical methods to data. However, the source and type of data place important constraints on the choice of statistical methods as well as on the warrant attributed to the causal claims based on the use of such methods. For example, much of the data used by people interested in making causal claims come from non-experimental, observational studies in which random allocations to treatment and control groups are not present. Thus, one of the most important problems in the social and health sciences concerns making justified causal inferences using non-experimental, observational data. In this paper, I examine one method of justifying such inferences that is especially widespread in epidemiology and the health sciences generally – the use of causal criteria. I argue that while the use of causal criteria is not appropriate for either deductive or inductive inferences, they do have an important role to play in inferences to the best explanation. As such, causal criteria, exemplified by what Bradford Hill referred to as "aspects of [statistical] associations", have an indispensible part to play in the goal of making justified causal claims

Rediscovery and redescription of Centrodora damoni (Girault) (Hymenoptera: Aphelinidae) from Australia, an egg parasitoid of Gonipterus spp (Coleoptera: Curculionidae), after nearly a century

Background Centrodora is a relatively common and widespread genus of morphologically diverse species, and is the most polyphagous genus known within the Aphelinidae, attacking eggs of insects in addition to pupae of Diptera and Hymenoptera, and nymphs of Hemiptera (Polaszek 1991). There are currently about 60 valid species in the genus, but given its morphological and biological diversity, some elevation of species-groups and subgenera to genus-level might be useful in future. Centrodora is represented in Australia by twelve species (Noyes 2015). New information Centrodora damoni (Girault) is redescribed and diagnosed from recently collected specimens reared from the eucalyptus weevil Gonipterus sp. near scutellatus Gyllenhal (Coleoptera: Curculionidae) from Tasmania, Australia. A lectotype is designated from a syntype specimen.© Ward S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.NHM Repositor

Electrochemical detection of oxacillin resistance with SimpleStat : a low cost integrated potentiostat and sensor platform

Testing outside the laboratory environment, such as point of care testing, is a rapidly evolving area with advances in the integration of sample handling, measurement and sensing elements widely reported. Low cost, simple to use systems are important in this context because they provide a route to devices that can be used outside the laboratory and could be implemented in low resource settings where advanced diagnostic testing is often unavailable. Here, we present an open source highly simplified electrochemical platform, called SimpleStat, that has been programmed to perform differential pulse voltammetry and can be used to detect the presence of OXA-1 DNA sequences for oxacillin resistance. This DNA sensor can be used to specifically detect the presence of the OXA-1 gene, contrasted to the tetA gene which encodes for tetracycline resistance. These measurements were performed with both polycrystalline gold electrodes as a benchmark and electrodes integrated into the SimpleStat printed circuit

Two new species of Eretmocerus Haldeman (Hymenoptera: Aphelinidae) parasitizing Aleurolobus rhododendri Takahashi and Dialeuropora decempunctata (Quaintance & Baker) (Hemiptera: Aleyrodidae) from Taiwan

Background: Species of Eretmocerus Haldeman develop as primary ecto-endoparasites of whiteflies (Rose and Rosen 1992). Currently, the genus Eretmocerus comprises 86 species worldwide, of which 11 species have been previously recorded from Taiwan (Shih et al. 2015). Despite having been recently revised for Taiwan, two new species are here added to the Taiwan fauna. New information: Two new species, Eretmocerus garrywardi Ward sp. nov. and Eretmocerus liangyihchoui Shih sp. nov. found parasitizing Aleurolobus rhododendri Takahashi and Dialeuropora decempunctata respectively, are described. A key to females of Eretmocerus species occurring in Taiwan is provided.© Ward S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.NHM Repositor

Development of a diagnostic device to detect different pseudomonas aeruginosa phenotypes in medically relevant contexts

Pseudomonas aeruginosa, widely present in the environment, is well known for its ability to cause infection in immune compromised individuals. For example, P. aeruginosa is the leading cause of morbidity and mortality in patients with cystic fibrosis (CF). Here, we describe how Electrochemical Impedance Spectroscopy (EIS) can be used to detect the presence of four different strains of P. aeruginosa. Using a low cost, screen printed carbon electrode significant changes can be seen in impedance data in the presence of P. aeruginosa after 24 hours. Furthermore, through the use of a normalization technique whereby the phase angle of the impedance (a commonly used parameter) is divided by a starting measurement, it is possible to identify differences between a non-mucoid and mucoid strain of P. aeruginosa. Sensors based upon the techniques described here could be used in a number of healthcare scenarios, where there is a need for low cost, real time detection of P. aeruginosa, such as CF

Solid friction between soft filaments

Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments' overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes' drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament's elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials

Social Disorganization and Rural/Urban Crime Rates: A County Level Comparison of Contributing Factors

Social disorganization theory (Shaw & McKay, 1929) is a common explanation for crime. However, few studies have examined its significance for the explanation of crime in rural areas. The current study utilizes county level data from the United States Department of Health and Human Services to examine common characteristics of social disorganization for both rural and urban areas and which of these factors greater contribute to crime rates. The findings are consistent with previous research that finds significant differences between urban and rural areas regarding causes of crime. Overall, this study found that common measures of social disorganization such as income, racial heterogeneity, and migration do play a significant role in predicting the crime rate for both urban and rural areas. However, births and international migration play a significant role only in rural areas