Molecular characterization of Listeria monocytogenes from natural and urban environments

Characterization of 80 Listeria monocytogenes isolates from urban and natural environments differentiated 7 and 26 EcoRI ribotypes, respectively. Whereas the majority of isolates from the natural environment represented L. monocytogenes lineage II (12 of 13 isolates), urban isolates grouped evenly into lineages I and II (32 and 33 isolates, respectively) and included two lineage III isolates. Multilocus sequence typing of all natural isolates and a randomly selected subset of 30 urban isolates showed a higher overall diversity (Simpson index of discrimination [D] of 0.987 and 0.920, respectively) than did EcoRI ribotyping (D = 0.872 and 0.911, respectively). Combined analysis with ribotype and lineage data for 414 isolates from farm sources, 165 isolates from foods and food-processing environments, and 342 human clinical isolates revealed that lineage I was significantly more common among human (P < 0.0001) isolates, whereas lineage II was more common among isolates from the natural environment, farms, and foods (P < or = 0.05). Among a total of 92 ribotypes, 31 showed significant associations with specific isolate sources. One ribotype (DUP-1039C) was significantly associated with both natural environments and farms. A spatial analysis showed a marginal association between locations in the natural environment positive for L. monocytogenes and a proximity to farms. Our data indicate that (i) L. monocytogenes strains from different sources show a high level of diversity; (ii) L. monocytogenes subtypes differ significantly in their associations with different environments, even though populations overlap; and (iii) a higher proportion of isolates from environmental sources than from human clinical cases can be classified into L. monocytogenes lineage II, which supports the classification of this lineage as an environmentally adapted subgroup.     

Transient simulations of the electrophoretic motion of a cylindrical particle through a 90° corner

The trajectory of a cylindrical particle driven by electrophoresis was transiently simulated as the particle moves through a 90° corner. A variety of system parameters were tested to determine their impact on the particle motion. The zeta potential, channel width, and particle aspect ratio were shown to have a minimal effect on the particle motion. Conversely, the initial vertical position of the particle and initial angle with respect to the horizontal had a significant impact on the particle motion. The presence of the 90° corner acts to reduce the initial distribution of angles to the vertical of 90° to less than 30°, demonstrating the possibility of using a corner as a passive control element as part of a larger microfluidic system. However, the reduction in angle is limited to the area near the corner posing a limitation on this means of control.     

基于DNA的分型方法有助于食源性病原体的鉴定

<正> 分型方法的进步增强了对食源性疾病的监测,但是将分型信息与流行病学数据进行整合以便迅速找到疾病大爆发的原因,仍然存在挑战。在1999年出版的一项研究中,我们已经评估了每年在美国引起大约7600万例食源性疾病的致病微生物,这其中包括325000例住院事件和5000例死亡事件(Mead等,1999)。为了能够更     

Analysis of counterfeit pharmaceutical tablet cores utilizing macroscopic infrared spectroscopy and infrared spectroscopic imaging

Advantages and limitations of analyzing authentic and counterfeit pharmaceutical tablets with both macro (nonimaging) attenuated total internal reflection Fourier transform infrared (ATR-FT-IR) spectroscopy and micro ATR-FT-IR spectroscopic imaging have been evaluated. The results of this study demonstrated that micro ATR imaging was more effective for extracting formulation information (sourcing), whereas a macro ATR approach was better suited for counterfeit detection (screening). More importantly, this study demonstrated that a thorough analysis of the counterfeit core can be achieved by combining the results of both techniques.     

Opportunities for biotechnology and policy regarding mycotoxin issues in international trade

Despite being introduced more than a decade ago, agricultural biotechnology still remains framed in controversy impacting both the global economy and international regulations. Controversies surrounding agricultural biotechnology produced crops and foods commonly focus on human and environmental safety, intellectual property rights, consumer choice, ethics, food security, poverty reduction and environmental conservation. Originally, some consumers were reluctant to accept the first generation agricultural biotechnology products because they appeared to primarily benefit agricultural producers; however, it is clear from continued evaluations that these technologies also improved both the safety and wholesomeness of food and helped improve the environment. Plants engineered to resist insect pests and tolerate less toxic pesticides resulted in improved yields thereby enabling farmers to produce more food per acre while reducing the need for herbicides, pesticides, and water and tilling. An indirect benefit of reduced pest damage in transgenic corn expressing genes to control insect pests is lower levels of mycotoxins, most notably those caused by the genus Fusarium. Mycotoxins are an important regulatory issue globally because of their toxic and carcinogenic potential to humans and animals. Complicating this issue is the fact that toxicological databases for mycotoxins are relatively incomplete compared to other food contaminants. Current debates about agricultural biotechnology and mycotoxins reveal significant differences in perception of associated risks and benefits. When faced with uncertainty, regulators tend to set limits as low as possible. Additionally, some regulators invoke the "Precautionary Principle" when limited information is available or disputes over interpretation exist for possible contaminants, including mycotoxins. A major concern regarding use of the "Precautionary Principle" is the appearance that regulators can justify setting any limit on the basis of inconclusive or unknown potential hazards of a contaminant which may significantly impact global trade because mycotoxin residues vary widely between countries. This paper describes the current economic and heath impact of these regulations and their impact on international trade.     

Attraction and Electroantennogram Responses of Male Mediterranean Fruit Fly to Volatile Chemicals from Persea, Litchi and Ficus Wood

Trimedlure is the most effective male-targeted lure for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). A similar response is elicited by plant substances that contain α-copaene, a naturally-occurring sesquiterpene. α-Copaene is a complex, highly-volatile, widely-distributed plant compound, and male C. capitata respond to material from both hosts (e.g., Litchi chinensis) and non-hosts (e.g., Ficus benjamina) that contain α-copaene. Avocado, Persea americana, recently was found to contain varying amounts of α-copaene in the bark and underlying cambial tissue. Short-range attraction bioassays and electroantennography (EAG) were used to quantify responses of sterile male C. capitata to samples of rasped wood from four avocado genotypes, L. chinensis, and F. benjamina. Gas chromatography-mass spectral (GC-MS) analysis was used to identify and quantify the major sesquiterpenes. Attraction and EAG amplitude were correlated, with L. chinensis eliciting the highest and F. benjamina the lowest responses. Responses to the avocado genotypes were intermediate, but varied among the four types. GC-MS identified 13 sesquiterpenes, including α-copaene, from all samples. Amounts of α-copaene in volatile collections from samples (3 g) ranged from 11.8 μg in L. chinensis to 0.09 μg in F. benjamina, which correlated with short-range attraction and EAG response. α-Copaene ranged from 8.0 to 0.8 μg in the avocado genotypes, but attraction and EAG responses were not correlated with the amount of α-copaene. Differences in enantiomeric structure of the α-copaene in the different genotypes and/or presence of additional sesquiterpenes may be responsible for the variation in male response. EAG responses were correlated with the amount of several other sesquiterpenes including α-humulene, and this compound elicited a strong antennal response when tested alone.     

Snow probe for in situ determination of wetness and density

The amount of water present in liquid form in a snowpack exercises a strong influence on the radar and radiometric responses of snow. Conventional techniques for measuring the liquid water content m_υ suffer from various shortcomings, which include poor accuracy, long analysis time, poor spatial resolution, and/or cumbersome and inconvenient procedures. This paper describes the development of a hand-held electromagnetic sensor for quick and easy determination of snow liquid water content and density. A novel design of this probe affords several important advantages over existing similar sensors. Among these are improved spatial resolution and accuracy, and reduced sensitivity to interference by objects or media outside the sample volume of the sensor. The sensor actually measures the complex dielectric constant of the snow medium, and the water content and density must be obtained through the use of empirical or semi-empirical relations. To test the suitability of existing models and allow the development of new models, the snow probe was tested against the freezing calorimeter and gravimetric density determinations. From these comparisons, valid models were selected or developed. Based on the use of these models, the following specifications were established for the snow probe: 1) liquid water content measurement accuracy=±0.66% in the wetness range from 0 to 10% by volume and 2) wet snow density measurement accuracy=±0.05 g/cm³ in the density range from 0.1 to 0.6 g/cm³     

Employee reactions to ergonomic job design: The moderating effects of health locus of control and self-efficacy.

A field survey of 180 municipal government office employees (82% women, 21–75 years old) investigated the potential moderating effects of internal health locus of control (HLOC) and self-efficacy on employees' reactions to ergonomic job design. Internal HLOC moderated the associations between ergonomic job design and somatic complaints and turnover intentions, and, to a lesser extent, job satisfaction. Self-efficacy moderated the associations between job design and job satisfaction, somatic complaints, and, to a lesser extent, persistent pain. Employees with low self-efficacy or low internal HLOC were influenced more by their physical job conditions than those with high self-efficacy or high internal HLOC. Implications for the ergonomic design of offices are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors associated with participation, attrition, and outcome in a smoking cessation program at the workplace.

Of 66 24–58 yr old smokers in 2 worksites, 67% participated in a smoking cessation program. 55% completed the program. Of those, 29% had quit smoking by posttest, and 17% were abstinent at the 6-mo follow-up. Different variables predicted participation, attrition, and outcome. Significant predictors of smokers who participated were length of cessation in previous abstinence attempts, number of years they smoked, and belief regarding personal vulnerability in contracting a smoking-related disease. Levels of pretest carbon monoxide and attitudes regarding adoption of smoking restrictions in the worksite predicted attrition. Posttest cessation was related to nicotine levels of cigarette brand smoked at pretest and pretest beliefs regarding postcessation weight gain. Abstinence at the 6-mo follow-up was predicted by number of co-workers who smoked and pretest concerns related to postcessation weight gain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A millimeter wave technique for measuring ice thickness on the Space Shuttle's external tank

The external fueltank of the Space Shuttle contains extremely lowtemperature propellents. A layer of material known as SOFI (Spray-On Foam Insulation) covering the outside of the fueltank provides thermal insulation between the aluminum surface of the fueltank and the ambient air. In spite of this insulation, under certain conditions ice formation will occur on the surface of the SOFI. Ice on the external fueltank can be detrimental to the launch and it is important to detect its presence and measure its thickness. This paper describes the design of a millimeter-wave radiometer technique developed for this purpose. The design is based on model calculations and measurements of the emission properties of a panel from the external fueltank performed at 35, 94 and 140 GHz. Two sets of measurements were performed, one for the unmodified rough-surface SOFI panel and another for a panel whose surface was sanded down to produce a smooth surface interface with the ice cover. The latter was used to evaluate the results of radiative transfer calculations which are much easier to perform for multilayer structures with plane boundaries. We present experimental evidence demonstrating that the technique developed can accurately predict ice thickness in the case of the smooth-surface SOFI panel. For the original (rough-surface) panel, the emission levels observed were considerably higher than predicted by the model. Both cases however exhibited comparable sensitivities to ice thickness (～ K/mm at 35 GHz, 4 K/mm at 94 GHz, and 5 K/mm at 140 GHz).