A conjugative plasmid, pOLA52, conferring resistance to the antibiotic growth promoter olaquindox has been isolated from Escherichia coli from swine manure. It also confers resistance to ampicillin and chloramphenicol and has a high frequency of transfer between strains of E. coli. Plasmid-borne olaquindox resistance has not been demonstrated before.The synthetic chemotherapeutic agent olaquindox has found wide use as a growth promoter in pig farming. It is active against coliform bacteria (3), where it inhibits DNA synthesis (10). Resistance has been defined with a breakpoint of 64 g/ml (3) or 50 g/ml (7). Until 2000, the compound has been allowed in concentrations of up to 100 mg/kg in feed for pigs younger than 4 months.Since the introduction of the compound in the 1980s, there has been some concern about whether resistance would arise and, if so, whether this resistance would be transferable and whether it would be linked to other resistance determinants (2, 5, 7). A survey study in Denmark has demonstrated the presence of a small fraction of olaquindox-resistant coliform bacteria in farm animals (3). Other studies have demonstrated increased resistance to olaquindox on pig farms using olaquindox. There was a slight correlation between resistance to olaquindox and resistance to chloramphenicol or ampicillin (5, 7). The aim of the present study was to find out if plasmid-bound olaquindox resistance exists.Isolation of a resistant bacterium. Swine manure from a farm using olaquindox as a feed additive was tested for the presence of bacteria able to grow on Gould S1 medium (4) with 100 g of olaquindox per ml. Diluted manure corresponding to 10 l of undiluted manure gave rise to three uniform colonies that did not show the fluorescence characteristic of fluorescent pseudomonads. One of the colonies was restreaked several times on Levine EMB plates (GIBCO Products for Microbiology: Technical Manual and Catalog; GIBCO Laboratories, Madison, Wis.) and Luria-Bertani (LB) agar plates (9), both containing 100 g of olaquindox per ml. Olaquindox (98% pure; ICN, Costa Mesa, Calif.) was added as a 10-mg/ml stock solution in 2.5 M NaOH; HCl was added to the final medium to counteract the high pH. All incubations were done at 37°C. The isolate was identified as Escherichia coli by use of the API 20E system (BioMérieux, Marcy l'Etoile, France).Olaquindox resistance was tested with an agar dilution test, while resistance to an array of other antibiotics was tested with Sensititre plates (1). The isolate was found to be resistant to ampicillin (MIC, Ͼ32 g/ml), kanamycin (MIC, Ͼ64 g/ml), chloramphenicol (MIC, Ͼ64 g/ml), nitrofurantoin (MIC, 128 g/ml), streptomycin (MIC, 128 g/ml), olaquindox (MIC, 128 g/ml), sulfamethoxazole (MIC, Ͼ512 g/ml), trimethoprim (MIC, Ͼ32 g/ml), and carbadox (MIC, Ͼ128 g/ml). The strain was sensitive to apramycin (MIC, 4 g/ml), ciprofloxacin (MIC, 0.125 g/ml), colistin (MIC, 1 g/ml), gentamicin (MIC, 0.5 g/ml), nalidixic acid (MIC, 16 g/ml), and tetracycline (MIC, 1 g/ml). In addition, the isolate did...
Purpose The purpose of this paper is to investigate how organizations create focal engagement objects through posts to their social media community members and how the members engage with these posts in ways that potentially co-create value. Of additional interest is the use of platform, tone and language to determine how they potentially influence value co-creation. Design/methodology/approach The research method is netnography. Two Australian-based cause organizations were selected for the study, and posts were collected from Facebook, Twitter and YouTube platforms used by the communities, as well as likes, clicks, shares and retweets. Data was examined using content and thematic analyses. Findings Findings for the characteristics of the posts indicate how platforms need to be member-centric and that post tone and language can be used for engaging members effectively. Three consumer engagement objects were thematically derived from the posts: events, donations and fundraising, and social justice that includes shout-outs and thunderclaps. In turn, consumer responses evidenced engagement sub-processes of co-developing, acknowledging, rewarding, sharing, advocating, adding momentum and learning. The likes, clicks, shares and retweets assisted in determining the amount of community interactions with posts in the cause brands’ communities. Research limitations/implications This research is limited to the extent it involved two cases. As with any cross-sectional research, the findings are snapshots of interactions on the two sites over the two-week data collection periods. Theoretical implications provide a deeper insights into value co-creation by empirically examining how organizations and their supporters employ and use post resources to co-create value collectively, and how the characteristics of the posts and behavioral interactions potentially facilitates this. Practical implications Managerially, this investigation will assist both commercial brand and cause brand organizations to plan and adapt their social media strategies to enhance supporters’ engagement with posts in this digital environment. Social implications The social implications of this study are that it provides an understanding of how cause organizations can harness online communities for value co-creation to generate social good. Originality/value The study is both original and adds value to the research community. The findings presented provide an insightful conceptual framework to guide future research into this important area of consumer engagement with resources in social media communities leading to potential co-creation of value.
When recording images with an atomic force microscope using the resonant vibrating cantilever mode, surprising strange results are often achieved. Typical artifacts are strange contours, unexpected height shifts, and sudden changes of the apparent resolution in the acquired images. Such artifacts can be related to the dynamical properties of the cantilever under the influence of the force between the tip and the sample. The damping of the cantilever oscillation can be either due to attractive interaction between the tip and the sample or due to a combination of attractive and repulsive interaction. The oscillating cantilever will be in a specific swing mode according to which type of interaction is dominating, and it is the switching between these modes that is responsible for a range of artifacts observed during image acquisition. This includes the artifact often referred to as "contrast reversal".The resonant vibrating cantilever mode [1, 2] of the atomic force microscope (AFM) is being increasingly used, e.g. in imaging of soft matter, a growing field. The vibrating cantilever mode is also particularly useful for the imaging of loose lying objects on substrate surfaces [3]. The main advantage of this mode of operation is the reduction of lateral forces between the tip and the sample when compared to operation in contact mode [2]. Moreover, there are now several reports about achievement of atomic resolution using the AFM under ultra high vacuum (UHV) conditions in the resonant vibrating cantilever mode [4,5]. This is an indication that detection using the high-Q resonant circuit constituted by the cantilever can be extremely sensitive. Additionally, the stiff vibrating cantilever allows the use of almost all kinds of vertical forces for detection including adhesive forces such as capillary forces and forces due to chemical bonding.When the vibrating cantilever is oscillating at amplitudes which are high compared to the extension of the tip-sample interaction potential, the tip and the sample are interacting only during a fraction of each swing cycle. Accordingly, roughly speaking, the effective force gradient experienced by the cantilever depends alone on the total amount of work done during the interaction period and on the oscillation amplitude and not on the specific functionality of the interaction potential. This does not imply, however, that the shape of the potential does not influence the motion of the cantilever. On the contrary, recent reports [6,7] have shown that the presence of long range attractive forces and short range repulsive forces generally facilitates two modes of operation where (1) the tip and sample interact purely attractively and (2) the interaction is both attractive and repulsive. In this article we show how this effect can influence imaging and result in a number of artifacts, including the often discussed "contrast reversal".All experiments were carried out under ambient conditions using a commercial microscope and commercial cantilevers [8]. The shown images were recorded using ...
In this paper we present a method for manipulating nanometer-sized particles on surfaces using a commercial atomic force microscope (AFM). A PC-mouse-based `click and move' manipulation scheme was implemented without the need for additional software or hardware development. The success of the scheme depends mostly on the choice of tip and cantilever which should be able to operate in both the contact mode and vibrating cantilever mode. Four different tip/cantilever combinations were tested and suitable types were found among those commercially available. The necessary properties are defined. The technique enables the fabrication of various kinds of two-dimensional structures of nanoparticles but may have relevance also to other areas of nanoscience, e.g. biotechnology. We developed the technique in order to study the magnetization of single nanoparticles using a very sensitive Hall micromagnetometer. The AFM is used as a tool to select and position a specific particle in the active region of the magnetometer.
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