The resistance to chemotherapeutic agents of Escherichia coli from domestic dogs and cats

The prevalence of antibiotic resistant Escherichia coli in the rectal flora of 168 healthy dogs and 93 cats in the Brisbane area was investigated. Rectal swabs were plated on MacConkey agar with and without antibiotics, and 690 isolates confirmed as faecal E. coli were tested for resistance to tetracycline, streptomycin, chloramphenicol, ampicillin, neomycin, furazolidone and sulphanilamide. Resistant isolates were obtained from 101 (60%) of the dogs and 24 (26%) of the cats sampled. A high percentage of the isolates was resistant to tetracycline, streptomycin, ampicillin and sulphanilamide. Multiple resistance to 3 or more of the drugs was exhibited by the majority of isolates and a total of 31 different multiple resistance patterns was demonstrated. Of the 50 strains tested for transfer of resistance, 30 (60%) transferred some or all of their resistance determinants to an E. coli K12F - recipient.     

Weed research: is it delivering what it should?

I believe the overall balance and current direction of much weed research is wrong, with too much emphasis on ‘scientific impact’ at the expense of practical application. For example, despite considerable research effort, Integrated Weed Management has not been widely adopted by farmers. Weed research, as a whole, has delivered less than it should have done in recent years, because of lack of appreciation of the difficulty and costs involved in scaling up experimental results to be applicable at a realistic field scale in real farming systems. In addition, there is often a lack of awareness of the complexities and resources needed to translate research results into actions that farmers, who may be counted in their millions, are willing to adopt. What is needed is truly integrated research, across the whole spectrum from basic to applied, with all elements contributing to real improvements in weed management. It should never be forgotten that, however great the ‘impact’ of a publication, it achieves nothing in terms of improving our ability to manage weeds until the results are used in practice. Effective technology transfer is essential. Weed research is an applied discipline, and the question needs to be asked repeatedly and critically, ‘Why study weeds?’     

Variation amongst isozymes of Rhynchosporium secalis

Mycelial extracts of 288 single-spore isolates of Rhynchosporium secalis. derived from infected leaves collected from seven barley cultivars at nine sampling sites, were subjected to horizontal slab polyacrylamide gel electrophoresis. A total of 28 patterns for α-esterase, four for β-glucosidase and one for β-galactosidase were obtained. One probable isozyme polymorphism, for α-esterase, was identified. There was no correlation between any particular band or pattern and either host cultivar or site.     

Influence of tillage, straw disposal system and seed return on the population dynamics of Alopecurus myosuroides Huds. in winter wheat

Alopecurus myosuroides Huds. was studied over a 2-year period in winter wheat established after tine cultivations or direct drilling. Straw was removed by baling or spread and burnt. Seed production was either allowed or prevented by cutting and removing all vegetation at the end of the first year. Cultivation differences had no consistent effect on plant or seed populations. Straw burning destroyed about 50% of seeds and encouraged the germination of surviving seeds. Weed populations in the crop were lower on burnt than on baled areas. Where seed shedding was allowed, populations of seeds in soil and plants increased by up to nine-fold per year. Straw burning resulted in smaller population increases. Seed decline in the soil averaged about 80% per year, so that less than 6% of the weed seeds sown were still viable after 2 years’burial in the soil. Most of the seed decline occurred between July and October and was slightly greater on burnt than on baled areas. Only part of this seed loss was accounted for by germination and emergence of seedlings during summer and autumn. Plants emerging in the crop represented less than 26% of viable seeds present in the soil at time of drilling the crop. Few seedlings emerged in spring. The viability of shed seeds varied with year and with weed density. High infestations were associated with lower seed viability and also fewer heads per plant.     

Collisions against Fences by Woodland Grouse in Scotland

A study was carried out in native pinewoods at Abernethy andGlen Tanar to investigate the effect of forest fences on capercaillieand black grouse. Collisions occurred at a rate of 0.25 and0.03 per km of fence per month for capercaillie and black grouserespectively. Male capercaillie had a higher proportion of severeand fatal collisions than females. Capercaillie tended to collidewith those sections of fence where there were moderately sizedpines (8.5 m) close (within 4.4 m) to the fence. Collision sitesclose to trees were most strongly associated with the heightof exposed trunk, suggesting that capercaillie fly under thecanopy and fail to see the fence. The annual mortality rateof radio-tagged capercaillie caused by collisions was 32 percent indicating that this was a major mortality factor. Collisionswere most frequent between September and November when capercailliewere dispersing. It is recommended that fences are removed whereand when they are unnecessary, or are made more visible, orare set back from old woodland.     

Responses to Pathogen-induced Disturbance: Decomposition, Nutrient Availability, and Tree Vigour

In the Oregon subalpine zone, extensive dieback occurs in relativelypure stands of 150 to 250-year-old mountain hemlock growingon very infertile soils. Tree death is caused by a root-rotfungus, Phellinus weirii. Young trees that become establishedfollowing death of the original forest are apparently not reinfectedby the pathogen until 80–140 years later. whereon mortalityoccurs again. We examined the effects.of this natural disturbanceand subsequent regrowth on a number of ecosystem characteristics. Decomposition rates and nitrogen availability measured by insitu exchange resins increased in the zones of young regrowth,but dropped to values common for old growth as the forest agedand the canopy closed. Phosphorus and potassium accumulationon exchange resins showed trends opposite to nitrogen, and mayhave been associated with changes in biomass. Increased nitrogenconcentrations and decreased lignin concentrations in fine rootsin the zone of young regrowth suggested improved tree nutritionunder conditions of higher N availability and lower leaf areaindex. Tree vigour, estimated as wood production per unit leafarea, also was significantly increased in the zones where youngforests grew. Circumstantial evidence suggests that increasesin nutrient availability and light following death of the matureforest improved photosynthesis leading to increased resistanceof young trees against infection by the pathogen.     

Some effects of burning cereal straw on seed viability, seedling establishment and control of Alopecurus myosuroides Huds.

Straw burning destroyed many Alopecurus myosuroides(blackgrass)seeds lying on the soil surface and, compared with straw baling, resulted in a smaller weed infestation in a subsequent direct-drilled winter wheat crop. The larger the amount of straw burnt, the higher the temperature reached on the soil surface and consequently the greater the control of the weed. Seeds that were fully imbibed were less susceptible to destruction by heat than were dry seeds. A shallow soil covering protected most seeds although some were stimulated to germinate. After straw burning the soil surface was a better environment for seed germination or seedling development than that under stubble. Differences in seedling numbers between treatments were not always proportional to differences in the numbers of viable seeds in the soil. Quelques effets du brûlage des pailles des céréales sur la viabilité des semences et l'implantation des plantules d'Alopecurus myosuroïdes Huds. et influence sur sa destruction Le brûlage des pailles a détruit de nombreuses semences d'Alopecurus myosuroïdes (vulpin) se trouvant à la surface du sol, ce qui a eu pour effet, par comparaison avec la récolte de la paille, de réduire l'infestation de la mauvaise herbe dans la culture suivante, un blé d'hiver en semis direct. Plus grande est la quantité de paille brûlée plus la température au niveau du sol est élevée et, par suite, meilleure est la destruction de la mauvaise herbe. Les semences qui avaient été complètement imbibées se sont montrées moins susceptibles d'être détruites par la chaleur que les semences sèches. L'existence d'une couche meuble superficielle sur le sol s'est révélée comme un meilleur environnement pour la germination des semences ou le développement des plantules que sous le chaume. Les différences entre le nombre des plantules selon les traitements n'ont pas toujours été proportionnelles aux quantités de semences viables présentes dans lesol. Einige Auswirtcungen des Verbrennens von Getreidestroh auf die Lebensfähigkeit der Samen, das Auflaufen und die Bekämpfung von Alopecurus myosuroides Huds. Das Verbrennen von Stroh zerstörte viele Samen von Alopecurus myosuroides(Ackerfuchsschwanz) die auf der Bodenoberfläche lagen und hatte, im Vergleich zum Ballenpressen, eine geringere Verseuchung in im Direktsaatverfahren nachgebauten Weizen zur Folge. Je grösser die Strohmenge war, desto höher war die Temperatur auf der Bodenotrerfläche und umso besser war die Bekämpfung des Ackerfuchsschwanzes. Samen, die mit Wasser vollgesogen waren, wurden durch die Hitze weniger geschädigt als trockene. Durch eine flache Bodenabdeckung wurden die meisten Samen geschützt, bei einigen wurde aber die Keimung stimuliert. Nach dem Strohverbrennen waren die Bodenverhältnisse für die Keimung und die Entwicklung der Keimlinge günstiger als in der Stoppel. Die Unterschiede in der Keimpflanzenzahl zwischen den Behandlungen waren nicht immer proportional zu den Unterschieden in der Anzahl lebensfähiger Samen im Boden.