Isolation and characterization of Listeria monocytogenes in Chinese food obtained from the central area of China

The objective of this study was to investigate the prevalence and characteristics of Listeria monocytogenes isolated from Chinese food, including frozen dumplings, flavored raw meat, roasted meat, braised meat, and a cold vegetable dish with sauce. A total of 900 food samples were collected from supermarkets, open-air markets, and delicatessens in three large cities in the central area of China to examine the presence of L. monocytogenes; 21 (2.3%) of the samples were positive for this pathogen. Among the different samples, braised meat showed the highest L. monocytogenes detection rate (4.4%). Samples obtained from delicatessens showed a much higher L. monocytogenes contamination rate (8.3%) than those from open-air markets (6.7%) or supermarkets (0%). Multilocus sequence typing (MLST) analysis indicated that the 21 bacterial isolates belonged to 12 ST subgroups. ST5 was the largest and contained 7 isolates (33.3%); it was followed by ST474, ST121 and ST9 (each containing 2 isolates [10.5%]). Antibiotic susceptibility analysis showed that the 21 L. monocytogenes isolates were thoroughly resistant to cefoxitin but highly susceptible to doxycycline and ciprofloxacin. The presence of 10 virulence genes was evaluated by PCR, which showed that inlA, inlC, inlJ, prfA, hlyA, and plcB were present in all isolates and that inlB, actA, plcA and iap were present in 71.4–90.5% of the isolates. This study provides a useful reference for risk assessment and control of L. monocytogenes contamination in Chinese food and for the treatment of clinical listeriosis.     

A synergistic approach to light-free catalysis using zinc oxide embedded multi-walled carbon nanotube paper

Nanoparticle embedded carbon nanotube papers can produce flexible functional films, whose function is based on the electronic coupling of the nanoparticles with the network of carbon nanotubes. Here we report on the expansion of a synergistic light-free catalyst system that requires both the molecular wire capability of multi-walled carbon nanotubes and the piezoelectric properties of ZnO nanoparticles. The electron–hole pairs can be induced by the piezoelectric effect of ZnO nanoparticles under the effect of pressure. The strong oxidizing radicals interact with the electron–hole pairs and aqueous solution to induce the degradation of methylene blue without the requirement of light. This study highlights the use of nanoparticles for the piezoelectric – light free catalyst system and the limitations of increased nanoparticle loading on the catalytic degradation of methylene blue.     

纯净水中病毒三种富集方法的比较

目的 比较膜吸附法、膜吸附-PEG法和膜吸附-超滤法对纯净水中病毒的富集效果,并对优选的富集方法的实验条件进行比对,旨在寻找高效的方法,为其他水体中病毒富集检测提供技术借鉴。方法 本文以MS2噬菌体为目标病毒,制作高、低浓度水样,建立逆转录-荧光定量聚合酶链式反应(RT-qPCR)方法的标准曲线,进行定量检测。使用膜吸附法、膜吸附-PEG法和膜吸附-超滤法富集水样,并比较不同过滤膜、不同超滤管及两种核酸提取方法的回收率,选择最适方法。结果 膜吸附-超滤法、膜吸附-PEG法和膜吸附法回收率均值分别为19.80%±12.19%、12.71%±9.09%和9.05%±4.89%,各因素对回收率的影响顺序为:膜吸附-超滤法>膜吸附-PEG法>膜吸附法;高浓度>低浓度。混合纤维素酯膜的富集效果优于尼龙膜。100 K和50 K的超滤管富集效果无差异。硅胶离心柱法和磁珠法核酸提取效果无差异。结论 通过二次富集可提高富集效率,膜吸附-超滤法优于另两种方法,且其操作简单、耗时短、对设备依赖性低,易于推广。膜吸附-超滤法的实验条件仍可优化、完善,拓展其在不同水体和不同病毒富集中的应用。     

Methods of choosing the optimal parameters for solid fuel combustion in stoker-fired boilers

Stoker-fired boilers are used for the combustion of coal and solid wastes. The most important disadvantage is their low thermal efficiency. The authors present methods of choosing the optimal rate of travel of the grid and height of the fuel layer basing on both realscale and laboratory measurements. Basing on industrial-scale experiments the authors calculated the optimal thermal efficiency and main energy losses using the least squares adjustment method. The stepwise regression method was used to correlate the main energy losses as functions of grid operating parameters. These correlations were used in the optimization method to estimate the optimal rate of travel of the grid and height of the fuel layer. The minimum retention time of the coal can be also calculated.     

2015年江苏省网店自制食品中食源性致病菌的 监测分析

目的 监测江苏省网店自制食品食源性致病菌的污染状况。了解金黄色葡萄球菌产毒及耐药特点。方法 GB4789《食品安全国家标准 食品微生物学检验》方法,选取无锡、常州、盐城等3个监测点,采集我省范围内的网店自制食品共214份,进行沙门氏菌、金黄色葡萄球菌、单增李斯特菌的检验。对分离得到的金黄色葡萄球菌进行葡萄球菌肠毒素检验和药物敏感性试验。结果 共检出食源性致病菌13株,总检出率为6.1%。其中金黄色葡萄球菌9株单增李斯特菌4株,未检出沙门菌。3份样品金黄色葡萄球菌污染超出国家食品限量值。9株金黄色葡萄球菌中6株产生葡萄球菌肠毒素。结论 江苏地区网店自制食品存在食源性致病菌污染状况。其中金黄色葡萄球菌污染比较严重,产肠毒素比例高,且对多种抗生素耐药,对青霉素产生普遍耐药, 对四环素、万古霉素和利福平耐药率较高, 对苯唑西林、环丙沙星、奎奴普丁/达福普汀和呋喃妥英等耐药率相对较低;对耐莫西沙星、利奈唑胺、替加环素和甲氧苄氨嘧啶/磺胺甲恶唑有较好的敏感性。     

A 12-month longitudinal study of Listeria monocytogenes contamination and persistence in pork retail markets in China

Listeria monocytogenes is a foodborne pathogen frequently isolated from raw pork meat. This study was designed to investigate the prevalence and molecular characteristics of L. monocytogenes in raw pork from open markets in China. The survey was conducted monthly over a 12-month period in Zigong, China. L. monocytogenes was isolated from 262 of 1641 samples collected (16.0%) including minced meat samples (131/608, 21.5%), pork pieces samples (111/857, 13.0%) and environmental swabs (20/176, 11.4%). The isolation rates in spring and winter were significantly higher than those in summer and autumn (X² = 68.85, P < 0.05). All isolates were subjected to serotyping, multi-locus sequence typing (MLST) and AscI pulsed-field gel electrophoresis (PFGE). The 262 isolates were subtyped into five serotypes: 1/2b (43.1%), 1/2c (35.5%), 1/2a (19.1%), 4b (1.1%), 3a (1.1%); 20 sequence types (STs) with four most frequent STs, being ST9 (35.9%), ST87 (19.8%), ST3 (16.0%) and ST8 (14.1%); and 39 pulsotypes (PTs) with PT4 (26.3%), PT30 (14.5%) and PT11 (12.6%) being most frequent. Two primary pulsotypes from pork pieces were previously isolated from clinical listeriosis cases in the local hospitals. The six markets from different districts differed in the level of contamination and strain types. Persistent contamination of L. monocytogenes was found in the markets especially in meat mincers, which were found to be one likely source of continuous cross contamination. These findings will help develop strategies to reduce L. monocytogenes contamination in open markets for better public health control and prevention of foodborne L. monocytogenes infections.     

Nurturing reflective teaching during critical-thinking instruction in a computer simulation program

Nurturing reflective teaching and improving critical-thinking instruction are two important goals in teacher education, but these are only achievable when teachers-in-training are provided with opportunities for building professional knowledge and for exhibiting reflective teaching practices. A computer simulation program (CS-TGCTS) was therefore developed here, and its effectiveness is explained in this study. From 149 preservice teachers participating in this study, a pretest–posttest control group design was defined by four student groups and two treatments. The central hypothesis was that increasing participants' self-awareness of teacher behaviors and enhancing mindful learning in professional knowledge would provoke reflective teaching and further bring about improvements in teacher behaviors. The findings support the hypothesis and suggest that the CS-TGCTS simulation is an effective vehicle for improving preservice teachers' reflective teaching in critical-thinking instruction.     

GDBC: A tool for generating global-scale distributed basin morphometry

In response to the vital role of geomorphological analysis in natural hazards study, geomorphology, distributed hydrology and other related disciplines, we present the first global basin morphometric product of 30 characteristics, 9 archived elementary including stream order, stream number, stream length, basin relief, basin length, basin perimeter, maximal flow length, down valley length and overland flow length, and 21 derivable from these elementary morphometric characteristics. Characteristics of basins discharging to every grid-cell of the global earth surface are generated at 30 arcsec resolution from the remotely sensed HydroSHEDS dataset. This product does not exist in previous literature because tree-structural grid-cells bring large computational redundancy to basin delineation and thus computing basin characteristics. To generate this product within a reasonable timeframe, we introduce in this paper an efficient framework to reduce the algorithm complexity to linear, O(N). We have presented a few geomorphologic findings using the generated product.     

Phosphoproteomic Comparison of Four Eimeria tenella Life Cycle Stages

Protein phosphorylation is an important post-translational modification (PTM) involved in diverse cellular functions. It is the most prevalent PTM in both Toxoplasma gondii and Plasmodium falciparum, but its status in Eimeria tenella has not been reported. Herein, we performed a comprehensive, quantitative phosphoproteomic profile analysis of four stages of the E. tenella life cycle: unsporulated oocysts (USO), partially sporulated (7 h) oocysts (SO7h), sporulated oocysts (SO), and sporozoites (S). A total of 15,247 phosphorylation sites on 9514 phosphopeptides corresponding to 2897 phosphoproteins were identified across the four stages. In addition, 456, 479, and 198 differentially expressed phosphoproteins (DEPPs) were identified in the comparisons SO7h vs. USO, SO vs. SO7h, and S vs. SO, respectively. Gene Ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of DEPPs suggested that they were involved in diverse functions. For SO7h vs. USO, DEPPs were mainly involved in cell division, actin cytoskeleton organization, positive regulation of transport, and pyruvate metabolism. For SO vs. SO7h, they were related to the peptide metabolic process, translation, and RNA transport. DEPPs in the S vs. SO comparison were associated with the tricarboxylic acid metabolic process, positive regulation of ATPase activity, and calcium ion binding. Time course sequencing data analysis (TCseq) identified six clusters with similar expression change characteristics related to carbohydrate metabolism, cytoskeleton organization, and calcium ion transport, demonstrating different regulatory profiles across the life cycle of E. tenella. The results revealed significant changes in the abundance of phosphoproteins during E. tenella development. The findings shed light on the key roles of protein phosphorylation and dephosphorylation in the E. tenella life cycle.