大肠杆菌0157的分离鉴定

0157为大肠杆菌的一种血清型,该血清型于1982年首次被鉴定为人发生该病的病因[1],在此之前这种血清型很少分离到.这种血清型归类为肠出血性大肠杆菌(EHEC),可以引起血痢和产生强毒素.据有关文献介绍,在采集的牛肉、猪肉和禽肉产品检测后曾有0157大肠杆菌的阳性报道.     

Further evidence that zinc sulphate compromises the efficacy of dipping treatments using diazinon to control sheep lice (Bovicola ovis)

Objective To compare the wettability and efficacy of diazinon dip wash made with and without the addition of zinc sulphate.
Design Field experiments using a shower and a plunge dip complemented by in-vitro wettability experiments.
Procedure A flock of infested sheep was divided into groups and treated in a shower dip with clear or cloudy dam water plus up to 1.5% zinc sulphate. Another infested line of sheep was treated using a plunge dip with nil or 1% zinc sulphate. In both experiments, wetting was assessed after dipping and louse counts were conducted for 9 months after treatment. Five in-vitro experiments compared the wettability of dip wash containing diazinon with up to 1.5% zinc sulphate added.
Results In the shower dipping experiment, live lice were found at 1 month after dipping in the cloudy water groups with 0.75%, 1.0% and 1.5% zinc sulphate and at 2 months in the 0.75% zinc sulphate group. No lice were found at subsequent inspections or at any time in the groups that were plunge dipped. Zinc sulphate decreased the amount of dip wash retained by wool staples in all in-vitro experiments (P < 0.05).
Conclusion Zinc sulphate should be considered as a risk factor that could cause failure to eradicate a lice infestation. The risk can be overcome by ensuring that all sheep are saturated at dipping and that the dip wash, and any holding tanks, are agitated throughout the dipping event.     

An Actinobacillus pleuropneumoniae arcA deletion mutant is attenuated and deficient in biofilm formation

Actinobacillus pleuropneumoniae is a facultative anaerobic pathogen of the porcine respiratory tract requiring anaerobic metabolic activity for persistence on lung epithelium. The ArcAB two-component system facilitating metabolic adaptation to anaerobicity was investigated with regard to its impact on virulence and colonization of the porcine respiratory tract. Using pig infection experiments we demonstrate that deletion of arcA renders A. pleuropneumoniae significantly attenuated in acute infection and reduced long-term survival on unaltered lung epithelium as well as in sequesters. Contrary to its role in enterobacteria, the deletion of arcA in A. pleuropneumoniae does not affect growth and survival under anaerobic conditions. Instead, other than the parent strain A. pleuropneumoniae DeltaarcA does not show autoaggregation under anaerobic conditions and is deficient in biofilm formation. It is hypothesized that the lack of these functions is, at least in part, responsible for the reduction of virulence.     

The control of lymphoid leukosis in a flock White Plymouth Rock chickens

Summary Lymphoid leukosis (LL) was successfully controlled in a commercial basic breeding line of White Plymouth Rock chickens. The control method has been developed for breeder flocks and consists of three elements: - In the flock under study, homogenates of embryos from all eggs collected during a number of I4-day periods are tested for the presence of LL viruses. - Only eggs from hens that have been shown not to shed virus in their eggs are used for the production of progeny. The offspring are reared in isolation during the first two months of life, at which time the age-related resistance against tumour formation by LL viruses appears to be sufficiently developed. - The chickens are subsequently inoculated intramuscularly with LL viruses of subgroups A and B transferred to a conventional chicken house. The vaccination raises a solid immunity to horizontal LL virus exposure and, due to the age-related resistance, tumour formation does not follow. No excretion of LL viruses could be detected in three generations of White Plymouth Rock chickens to which the three elements of the control procedure were applied. Clinical disease was not observed in any of the chickens under notice.     

Factors Associated with Dough Stickiness as Sensed by Attenuated Total Reflectance Infrared Spectroscopy

Attenuated total reflectance (ATR) and Fourier transform infrared (FTIR) spectroscopy have been applied in the characterization of sticky dough surfaces. The characterization provides insight in the chemical distribution of gluten protein, starch, water, and fat during dough kneading. ATR is especially useful for selective sampling of dough surfaces because the depth of penetration of radiation is quite shallow. For dough, it is calculated to be in the order of 0.5–4 μm in the mid‐infrared, ideal for measurements of stickiness effects, where only the dough surface is of interest. To investigate the cohesive and adhesive properties of the individual dough constituents, dough was peeled from the ATR plate to study the material that adhered to it. The infrared spectra obtained indicate that fat and gluten protein appear to be located at the outer sticky dough surfaces, rather than water and starch. In comparison with gluten, the fatty component showed relatively strong adhesive forces to the ATR plate; a high residual fraction was measured after peeling the dough. Gluten proteins display different cohesion and adhesion properties that are strongly dependent on their hydration state. This indicates that the degree of hydration of gluten proteins contributes to the sticky properties of (overkneaded) dough. When analyzing gluten protein in D₂O instead of a dough matrix, more or less similar results were obtained. Significant differences in amide I and amide II intensities were measured for kneaded and stretched gluten protein in comparison to untreated, wet gluten. Besides changes in the vibrational properties of the amide groups, conformational changes in the tertiary protein structure also were observed. It appears that kneading and stretching of dough results in a major decrease in α‐helices content, accompanied by an increase of extended β‐sheet conformations.     

The relationship of scrotal circumference to testicular weight in rams

Scrotal circumference (SC), testicular diameter (TD) and testicular weight (TW) were measured at necropsy of 148 Merino rams of varying age (yearling: 110, 2- to 3-year-old: 5, 4-year-old: 28, greater than 7-year-old: 5). These rams, although culled from flocks in north western Queensland for poor conformation or advancing age, had no clinically palpable or gross necropsy lesions of the genitalia. Despite the fact that SC measurement was performed at necropsy on scrota with greatly varying wool cover and its diverse content of plant material (burrs and grass seeds), the correlation of SC with TW was positive, high and significant (r = 0.92, P less than 0.01). This correlation was greater than that between TD and TW (r = 0.91, P less than 0.01) even though both were measured after dissection of the scrotal contents. The clinically convenient SC measurement deserves wider application as an estimate of testicular weight and therefore fertility in rams.     

Evaluation of the nutritional value of prototype lupin protein concentrates when fed to rainbow trout (Oncorhynchus mykiss)

This study examines the palatability and discrete nutritional evaluation of some prototype lupin protein concentrates (PC) when fed to rainbow trout. Products were developed from both Lupinus angustifolius and Lupinus luteus kernel meals with an increase in protein of 415 g/kg DM to 690 g/kg DM for L. angustifolius and 545 g/kg DM to 750 g/kg DM for L. luteus, respectively. This study completes a three-phase approach to evaluating the nutritional value of these products. The digestibility of energy, nitrogen, phosphorus and organic matter were determined in earlier studies using the diet substitution approach. The apparent digestibility of the energy from the L. angustifolius PC and the L. luteus PC along with the apparent protein digestibility were used to formulate two series of experimental diets to examine both the palatability and discrete nutritional value of the products. Serial inclusion of either PC at 0%, 10%, 20%, 30% and 40% into a typical salmonid diet specification allowed an examination of the palatability of each product. Additional negative controls, based on the 0% diets with inclusion of sulfamerazine sodium, were included in the experiment to demonstrate the capacity of the experiment to detect significant palatability issues. No significant effects of inclusion of either PC on any fish performance criteria, such as feed intake or growth, were identified. In contrast, significant reductions in feed intake and consequently growth were observed from fish fed either of the negative controls. This experiment demonstrated that each PC was highly palatable at inclusion levels up to and including 40% of the diet. Using a protein-limited-restrictively-fed experimental approach the discrete nutritional utilisation of each PC was defined. Growth of fish fed the PC treatments was not significantly different to that of the 0% reference diet. Two control diets with substitutions of cellulose to an equivalent inclusion level to that of the PC have provided an indication of the net benefit of the test ingredients. This experiment demonstrated that each PC provided equivalent nutritional value to the fish at either of the two inclusion levels (20% and 40%) evaluated. These PCs differed in their viscosity and gelling properties which may allow feed manufacturers the opportunity to manipulate the physical attributes of their feeds. Together, these studies clearly show that the prototype PCs have substantial potential as a prospective feed ingredient for the aquaculture sector.     

Pathology of skin diseases in crocodiles

Objective To establish which skin diseases occur in crocodiles, particularly those on farms, to indicate the relative frequency of each particular disease and to provide information on pathogenesis, especially in regard to lesions with two or more pathogens present.
Design A gross and microscopic retrospective (period of 1989 to 1995) and current (1996 to 1997) examination of skin lesions in crocodiles in Queensland and the Northern Territory.
Result Skin lesions were obtained from crocodiles on nine farms, from a group of experimental animals and from one adult found dead in the wild. A total of 203 lesions from 180, mostly young, crocodiles was examined; 119 lesions were from retrospectively examined cases and 84 were recent. The relative frequencies of four presumed primary pathogens in lesions were Dermatophilus s p 28.1 %, fungi 14.8%, poxvirus 3.4% and probable Mycobacterium s p 2.5%. In addition, other bacteria of unknown significance were present in many lesions, and there was one case of presumed Paratrichosoma crocodilus infection. In 32.5% of lesions, multiple pathogens were identified.
Conclusion Dermatophilosis is the most common and probably the most important skin disease of crocodiles in Australia, but it is frequently complicated by concurrent infection with fungi or other microorganisms.     

Modelling responses to nutritional, endocrine and genetic strategies to increase fertility in the UK dairy herd

The United Kingdom, as in most countries using intensive dairy management programmes, is facing serious challenges in terms of dairy cow fertility, as highlighted by a rapidly increasing calving interval (CI). A mechanistic, mathematical model is described that predicts the size of the future national dairy herd required to supply domestic requirements and its inherent sustainability in terms of production of replacement female numbers. The results from the model suggest that continuing use of current management strategies may result in the national dairy herd being unsustainable due to increasing CI and reduced fertility in as few as 10 years. Adoption of nutritional, endocrine and genetic techniques that increase fertility can effectively and rapidly reverse this trend and reduce the required size of the national herd, thereby reducing methane emissions from dairy production.