Detection of Mycobacterium tuberculosis complex in milk using polymerase chain reaction (PCR)

Organisms of the Mycobacterium tuberculosis complex (TBC) are responsible for tuberculosis, a chronic disease which represents a serious public health problem in the world. The most common means of contracting the disease are through inhalation of aerosols, drinking of unpasteurised milk from an infected cow and the sharing of common water or feed sources.In this study a rapid, sensitive and reliable PCR-based method for specific detection of the Mycobacterium TB complex directly from raw milk samples was developed. The DNA extraction method was effective and able to remove inhibitors and allowed the isolation of amplifiable DNA. The procedure demonstrated the presence of the TBC mpb70 gene in 36/50 (72%) of Albanian milk samples tested. The study highlights the need to screen extracommunitarian milk to define an epidemiological background and to guarantee the quality of the raw milk in countries lacking a suitable TB-infection control plan.     

食源性致病菌研究动态

正食源性病原菌是引起食源性疾病的主要原因之一,是全球食品安全的核心问题,已成为威胁人们健康的重要公共卫生问题。近年来,国内外食源性病原菌病事件频频发生,在我国,由于食物链中病原细菌污染及其造成的食源性疾病也屡见不鲜,不仅严重危害国民健康,而且已经成为我国食品出口的主要障碍,严重损害了我国的国际形象。因此,我国应加强对食源性细菌病的研究和防控工作。本文将简要介绍食源     

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.     

Genetic identification of the caviar-producing Amur and Kaluga sturgeons revealed a high level of concealed hybridization

China has recently become the leader country for sturgeon aquaculture and caviar production, deeply changing the traditional geography of this market in few years. As a consequence, some species originating from the Far East Asia increased their economic relevance, joining the ones traditionally harvested for caviar. In this context, the possibility to reliably and promptly identify these species on the market has increasing importance for the enforcement of control actions against illegal trade or commercial frauds. The present study focuses on two commercially relevant species, massively reared in China not only as pure species but also as reciprocal hybrids: the Amur (Acipenser schrenckii) and Kaluga (Huso dauricus) sturgeons. We assess the identification power of two putatively diagnostic markers isolated from two predicted introns of the nuclear coding gene Ribosomal Protein L8. The markers were tested on tissue or caviar of 508 individuals of the two species and 31 hybrids. In order to compare results across loci, most individuals were also checked at two already published microsatellite markers, with a good, even if incomplete, identification efficiency for the two species. No marker showed fixed alternative alleles between Amur and Kaluga sturgeons, confirming the difficulty of distinguishing these two sympatric species in spite of the marked morphological differences and the consequent classification into different genera. So far, the multi-locus panel here used represents the more effective tool for the genetic identification of pure Amur and Kaluga sturgeons and resulted to be fully efficient to validate caviar and tissues obtained from hybrids between the two species.     

Local area supervisory protection system transformer taps

Connecting a transformer directly to the high voltage transmission line is a practical and relatively inexpensive way of providing service. The use of many circuit breakers is usually not justified, particularly at higher voltages. Motor operated air break switches (MOABs) instead of circuit breakers are used. To cope with the difficulty of switching arrangements, detection and clearing of transformer faults excluding the ground switch for MOABs operation, local area supervisory protection (LASP) system is proposed. LASP System collects current and voltage data from different locations on the power system through integrated equipment (IE) to relay equipment (RE). Asynchronous transfer mode (ATM) is a connection-oriented, packet-switched networking model between the LASP system and the equipment. Some attention is given to the architecture of a solution and some guidelines as to how this structure might be built to match with the next generation substation network architecture are also provided. The environment opens up new vistas for protection applications in the power systems.     

Fabrication of platinum thin films for ultra-high electrocatalytic hydrogen evolution reaction

While the noble metals (e.g., platinum, (Pt)) remain the benchmark electrocatalyst for the hydrogen evolution reaction (HER), their mass production require a reduced metal loading and faster fabrication protocols. The aim of the present work is to prepare Pt thin films by simple and fast fabrication technique, and to evaluate their performance for HER. The thin films of Pt are grown on two substrates, namely titanium foil (Ti) and nickel foam (NF), using a single step aerosol assisted chemical vapor deposition (AACVD) method. The film deposition time are varied from 20 to 60 min. Microscopic analyses suggest a gradual evolution of the films into percolated and/or porous nanostructures, a feature that remains highly desired to allow the maximum access of active sites. The performance of the as-prepared electrodes is evaluated by monitoring the HER in acidic electrolyte. The Pt film on nickel foam (Pt/NF) exhibits better electrical conductivity and smaller charge transfer resistance, while the film deposited on the Ti foil (Pt/Ti) demonstrates superior catalytic activity per active sites. The as-prepared Pt/Ti and Pt/NF electrodes produce 10 mA cm⁻² at overpotential of 28 mV and 26 mV, respectively, better in performance than commercial Pt/C electrode (~39 mV), set a new bench mark electrocatalyst for the HER.     

食源性大肠杆菌噬菌体的分离及其特性分析

目的从污水样品中分离致病性大肠杆菌的烈性噬菌体,分析其生物学特性,为食品中致病性大肠杆菌的控制提供参考。方法以标准菌株Escherichia coli EPEC(CICC10664)为宿主菌,采用双层平板法,从扬州市各地污水中分离纯化噬菌体,通过透射电镜观察其形态、测定最佳感染复数、一步生长曲线、裂解镨及其对宿主菌生物被膜的影响。结果分离到一株肠致病性大肠杆菌烈性噬菌体,命名为Ec.P01,电镜观察其为肌尾噬菌体,直径约为80 nm,最佳感染复数为0.01,一步生长曲线显示其噬菌体Ec.P 01的平均裂解量为48 PFU/m L,潜伏期约为10 min,裂解期约为90 min,热稳定性较好,对宿主菌生物被膜的形成有明显的抑制作用。结论本研究分离到一株肠致病性大肠杆菌烈性噬菌体,为治疗大肠杆菌感染疾病和治理食品及其环境污染提供新的思路与方法。     

Assessment of high intensity ultrasound for surface decontamination of salmon (S. salar), mackerel (S. scombrus), cod (G. morhua) and hake (M. merluccius) fillets,and its impact on fish quality

The effect of applying high intensity ultrasound on microbiological and quality parameters in several fish species was assessed at laboratory scale. Samples of salmon (S. salar) and mackerel (S. scombrus) as oily fish, and cod (G. morhua) and hake (M. merluccius) as white fish, were treated using an ultrasonic bath (30 kHz). Samples of each species were separated into three groups (i) untreated control (C), (ii) water immersion only (IM) and (iii) ultrasound (US) and treated for 5, 15, 25, 35 and 45 min. All physicochemical parameters were determined in samples treated for 45 min. Microbiological counts were reduced significantly (p < 0.05) after US treatment in oily fish species with reductions of up to 1.5 & 1.1 log CFU/g for psychrophilic and mesophilic viable counts (PVC & TVC) observed in salmon and mackerel respectively. Corresponding reductions in white fish species were only 0.5 log CFU/g. Lipid content did not change significantly (p > 0.05) after treatment. Significant reductions of thiobarbituric acid reactive substances (TBARS) values (C: 0.36; US: 0.18) and colour changes were observed in salmon (a* C: 12.8; US: 10.0). Moisture levels increased by 8% following US treatment in hake.     

Platinum nanoparticles deposited nitrogen-doped carbon nanofiber derived from bacterial cellulose for hydrogen evolution reaction

The nitrogen-doped carbon nanofiber derived from low and high proportion polyaniline doped bacterial cellulose (BC) was obtained via polymerization followed by pyrolysis. The resulting products were named LN-BC and HN-BC accordingly. Platinum nanoparticles modified LN-BC and HN-BC was then prepared (Pt@LN-BC and Pt@HN-BC) via electrochemical deposition. The morphologies of LN-BC and HN-BC indicated that the BC lost its nanowire structure after polyaniline modification and pyrolysis under nitrogen atmosphere. Platinum nanoparticles with diameters ranging from 3 to 5 nm can be well dispersed in the HN-BC support. The HER performance of Pt@LN-BC and Pt@HN-BC was fully investigated. Electrochemical results showed that the Pt-based catalysts had better HER activity than the Pt free catalysts in acid, indicating the HER activity was mainly from Pt. Besides, Pt@HN-BC had better HER activity than Pt@LN-BC in acid, suggesting N-doping rate was an important factor in enhancing HER activity. And the 10Pt@HN-BC (deposition for 10 s) with 4.38 wt% Pt loading was the best HER catalyst among the Pt@HN-BC. The onset potential (@ ?1 mA cm^?2) and overpotential (@ ?10 mA cm^?2) of the 10Pt@HN-BC in 0.5 M H₂SO₄ is ?18 and ?47 mV, respectively. The corresponding Tafel slope was ?35 mV dec^?1, which is quite comparable to that of Pt/C (10 wt%). The electrochemical double layer capacitance (C_dl) and turnover frequency (TOF) were estimated and presented in the work. Long-term stability test confirmed that the 10Pt@HN-BC had excellent stability, which was important for practical application.