用免疫分离法检测稻种上的白叶枯病菌

 免疫分离法是一种新型的、高度灵敏和准确的种菌带菌检验法,它结合了利用专化性抗血清的选择法吸附作用和活细菌可形成菌落的两方面的优点,从种苗材料中分离到目标细菌,用纯菌测试它的回收率为50~70%,最低检出率为50~100个菌/ml,人工喷接种和病田收获的病种带菌率达87%,平均每粒自然病种上的细菌数在100个左右。免疫分离所得菌落经致病性测定,大多数为白叶枯菌。     

昆虫病原斯氏和异小杆线虫人工大量培养的研究概况

昆虫病原斯氏和异小杆线虫的大面积田间应用要求线虫有效地生产，本文介绍业已建立线虫大量培养方法及合适于大规模生产线虫的工厂化培养系统及有关的技术参数，并讨论其优化管理问题。     

Bacterial and fungal pathogens isolated from corneal ulcerations in domesticated elephants (Elephas maximus maximus) in Sri Lanka

Infective corneal diseases are common among the domesticated elephants in Sri Lanka, causing morbidity including blindness leading to loss of revenue to their owners. From 140 elephants of different ages and both sexes, 36 animals (25.7%) had evidence of keratitis, corneal ulcers, corneal opacities, and some had foreign bodies in their eyes. Nine elephants (6.4%) had lesions in both eyes (6.41%). Cultures for both bacteria and fungi were obtained from 26 corneal ulcers, including the nine elephants with bilateral lesions. The other 10 animals could not be restrained for sample collection. Swabs from the normal corneas of an additional 20 elephants without signs of any ophthalmic diseases were also collected. Twenty-three of the 35 (65.71%) samples from affected corneas yielded bacterial pathogens, and 14 (40%) also had fungal isolates. None of them yielded a fungal isolate alone. The predominant bacteria isolated were Staphylococcus aureus , beta hemolytic streptococci and coliforms. Fusarium , Cladosporium , Curvularia and Aspergillus species were the primary fungal isolates. No bacteria or filamentous fungi were isolated from the eyes with the normal corneas. Microbial identification including fungal isolations is suggested in the management of infective corneal diseases in elephants.     

Impact of Mastitis Control Measures on Milk Production and Mastitis Indicators in Smallholder Dairy Farms in Kiambu District,Kenya

Bovine mastitis and mastitis control were investigated on smallholder farms in central Kenya. After an initial observational study, a clinical trial to assess the impact of three different mastitis control strategies – (1) improved udder hygiene, (2) treatment of subclinical cases, and (3) a combination of these – was conducted on 100 randomly selected farms with 332 lactating cows. Before the implementation of control measures, the milk yield was low (mean 6.5 kg/day; median 6 kg/day) and somatic cell counts (SCC) were high, with 80% and 43% of cows having milk with SCC greater than 250×10³ cells/ml and 600×10³ cells/ml, respectively. Infectious pathogens were also commonly isolated, with 63% of cows being positive for pathogenic bacteria. Neither intervention strategy alone had any effect on mastitis indicators or milk yield. In combination, the measures had some impact, lowering the prevalence of contagious pathogens by 18%, but this was not reflected in a significantly increased milk yield, lowered SCC or reduced incidence of clinical mastitis.     

Characterizing the complexity of landscape boundaries by remote sensing

This paper presents a method for characterizing the complexity of landscape boundaries by remote sensing. This characterization is supported by a new boundary typology, that takes into account points where three or more landcovers converge (i.e., convergency points or coverts). Landscape boundary richness and diversity indices were proposed and calculated over 19 landscapes in South-East Brazil. Results showed that landscape boundaries, especially convergency points, provided an enrichment in landscape pattern analysis. Landcover boundary diversities were significantly related to landcover shape: elongated riparian units had the highest values for boundary diversity and coverts proportion indices. On the other hand, landscape analysis showed that indices of shape, richness, diversity and coverts proportion provided an additional evaluation of landcover spatial distribution within the landscape.     

Mastitis Whey — a Good Medium for Bacteria?

Growth of mastitis pathogenic bacteria was measured in bovine whey samples by a turbidometric microtechnique. Whey from mastitis cows supported growth as compared with whey prepared from normal milk. Blood proteins leak into milk during mastitis. A study was undertaken to analyze which molecules from blood would promote bacterial growth in whey Fractions containing hemoglobin showed a distinct growth-promoting effect. An inadequate iron supply is one of the restricting growth factors for bacteria in milk. By utilizing heme-compounds the pathogens can by-pass the effect of antimicrobial iron-binding present in milk in the form of lactoferrin.     

Seasonal effects on the aerobic bacterial and fungal conjunctival flora of normal thoroughbred brood mares in Florida

Objective To evaluate seasonal effects on the presence or absence of fungal and aerobic bacterial flora of the conjunctival fornix of normal Florida Thoroughbred horses. Sample population Both eyes of 100 horses. Procedure Horses with normal anterior segment ophthalmic examinations from three farms in north central Florida were included. Each animal had the ventral conjunctival fornix of each eye swabbed with sterile culturettes. Samples were taken in October, January, April, and July (1999–2000). Aerobic and fungal cultures were plated. Bacterial cultures were reviewed at 24 and 48 h. Fungal cultures were reviewed weekly for 4 weeks. Logistic regression analysis with season as a factor and age of the horse as a covariate was performed. Statistical significance was set at P < 0.01. Results Horses ranged from 3 to 24 years of age, with a median age of 9 years. Twenty‐four genera of bacteria and 35 genera of fungi were recovered. Corynebacterium sp., Staphylococcus sp., Bacillus sp. and Moraxella sp. were the bacteria most frequently isolated. Mold species, dematiaceous mold species, Chrysosporium sp., Cladosporium sp., and Aspergillus sp. were the most frequently recovered fungi. Season did not have a significant effect on the presence of microorganisms isolated for individual horses adjusted for age. Younger horses had an increased incidence of gram‐negative rods and fungal isolates. The number of bacteria and fungi isolated are not uniform across seasons. Conclusion There were no significant differences between the number or type of organisms cultured during the sampling seasons in normal Florida horses. A large range of normal bacterial and fungal flora were isolated from these horses. The number of bacteria and fungi isolated are not uniform across seasons. The likelihood of detecting an organism depends on the horses’ age.     

The loss of genetic diversity in Dabry's sturgeon (Acipenser dabryanus,Dumeril) as revealed by DNA fingerprinting

• 1. Dabry's sturgeon, a large, long‐lived migratory fish is endemic to the Yangtze River. Over‐fishing and habitat destruction have caused large‐scale declines in natural stocks in the last two decades.
• 2. Examining patterns of genetic diversity has become an integral component of many management plans for endangered species. DNA fingerprinting was applied to detect genetic diversity in Dabry's sturgeon collected in 1958–1959, 1980–1981 and 1998–1999.
• 3. Studies on direct genetic parameters (genetic variability, hypervariable loci and heterozygosity) and indirect parameters (band‐sharing coefficient and allelic frequency) showed that the continuous decline in wild populations has caused the loss of genetic diversity in present‐day sturgeon.
• 4. The present‐day populations have the lowest genetic variability; thus, effective management is needed to preserve genetic diversity.
• 5. A conservation strategy is urgently required, comprising artificial rearing facilities coupled with breeding management plans.

Copyright © 2003 John Wiley & Sons, Ltd.     

Prevalence and Aetiology of Mastitis in Cows from Two Major Ethiopian Dairies

The study was undertaken to determine the aetiology and prevalence of mastitis in hand-milked cows (n = 186) in two major Ethiopian dairies. The California Mastitis Test and culturing for bacteria revealed that 21.5% of the cows were clinically infected and 38.2% had subclinical mastitis. Most mastitis pathogens isolated from milk samples testing positive by the California Mastitis Test were Gram-positive cocci. Staphylococci constituted 57% of the isolates, of which the predominant cause of bovine mastitis was Staphylococcus aureus (40.5%). Other mastitis pathogens isolated include streptococci (16.5%), coliforms (9%) and corynebacteria (5%). Retrospective analysis of farm records indicated that mastitis was the second most important cause of culling and accounted for 27% of the cows removed from these two dairies.     

Protective Effects Against Erwinia amylovora Induced by hrp Mutants in the Whole Plant are Only Partially Mimicked in Cultivated Cells

A virulent strain of Erwinia amylovora, the causal agent of fire blight of Maloideae, and two of its non-virulent hrp mutants (a secretory and a regulatory mutant) were inoculated into apple cell suspensions either alone or in mixed inoculations. In single inoculations, death of 4- to 5-day-old apple cells occurred only when the concentration of the virulent strain of E. amylovora reached a threshold inoculum concentration of 10⁴CFUml^–1, while high concentrations of the hrp mutants were unable to kill apple cells. When mixed inoculated with the virulent parental strain, both hrp mutants protected apple cells from death caused by the virulent strain. The protective effect was associated with a decrease in the population level of the virulent strain and it was dependent on the non-virulent to virulent inoculum concentration suggesting a competition between the non-virulent mutant and the virulent strain. However, no differential protective ability between the two types of mutants could be noticed, contrary to previous results obtained with apple seedlings or apple flowers in which the regulatory mutant was significantly more effective than the secretory mutant. In conclusion, inoculation of apple cell cultures with E. amylovora does not seem to be a model suitable for investigating mechanisms leading to protection.