Rapid and standardized methods for detection of foodborne pathogens and mycotoxins on fresh produce

Due to the increase in consumption of fresh produce regarding to the health demand in the last decades, a considerable portion of foodborne outbreaks has been trackbacked to contaminated fresh produce, which have appeared as highly possible vehicles for foodborne outbreaks nowadays. Delays in detection of pathogens and mycotoxins on fresh produce hindered the trace-back investigations in finding the source and revealed the urgent need of rapid and reliable methods. In the frame of this review, we summarized available fast, reliable and standardized methods (conventional, molecular, rapid and recently developed methods) used for detection of the most common foodborne pathogens and mycotoxins which are the most likely causative agents of outbreaks caused by contaminated fresh produce.     

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 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.     

Prevalence of virulence genes in Escherichia coli isolated from food in Casablanca (Morocco)

This study was undertaken to determine the frequency of potentially pathogenic Escherichia coli (E. coli) strains among E. coli isolated from Casablanca, Morocco. The E. coli strains were isolated from ground beef (n = 140), turkey (n = 200), sausage (n = 120), seafood (n = 60), domestic water (n = 35) and well water (n = 50). The prevalence of E. coli was 48%, 45%, 35.5%, 30%, 8.3%, 0%, for well water, ground beef, turkey, sausage, sea food and domestic water, respectively. Two hundreds E. coli isolates were tested for the presence of 17 virulence genes associated with strains causing intestinal and extra-intestinal infections. The virulence genes included stx1, stx2, lt, st, hlyA, aggA, saa, astA, iucD, cnf1, eaeA, bfpA, ial, ipaH, afa, pap and sfa. PCR showed that 37% (74) of E. coli isolates carried one or more of these virulence genes. No virulence genes were found in E. coli strains isolated from sea food samples. In contrast, 10% of the ground beef samples, 18% of the turkey samples, 17.5% of sausage samples and 6% of well water contained specific factors for intestinal E. coli pathogens.     

Potential impacts of emission concerned policies on power system operation with renewable energy sources

Electricity sector is considered as major source of green house gas emission. A huge opportunity exists within this sector to cut down the emission and contribute significantly to mitigate the climate change. The Emission Trading Schemes (ETSs) and inception of renewable energy sources (RESs) into the generation mix contribute to the reduction of emission and impact electricity market operation. This paper investigates the impact of emission concerned policies, such as: (a) fixed emission quota; (b) cap and trade; and (c) bilateral contract commitments; on the operation of power system. The renewable support mechanisms, such as renewable purchase obligation (RPO) and feed-in-tariff are incorporated so as to account the relative costs of cleaner and renewable generation technologies. Each generator is allocated certain amount of emission allowances, which they can use to cover emission during energy generation. The electricity and emission prices are obtained from the interaction of carbon and energy market. It is observed that, the renewable support mechanisms affect the generating and emission trading schedule of independent power producers (IPPs). They help them meet their emission targets and increase overall welfare. A balance between the emission regulation and renewable support mechanisms is essential, otherwise they make each others effect redundant. The performance of the proposed model is demonstrated by its implementation on a five generators system.     

Survey of prevalence and seasonal variability of Listeria monocytogenes in raw cow milk from Northern Italy

Listeria monocytogenes is an important food-borne pathogen causing meningitis, meningo-encephalitis and abortion. Both sporadic and epidemic human listeriosis cases are associated with the consumption of contaminated foods. To assess the potential risk to consumer health, the presence of L. monocytogenes was investigated using qualitative and quantitative methods in raw milk (bulk tank milk and milk for vending machine) collected from 2010 to 2013 in Northern Italy (Lombardy and Emilia-Romagna regions). Overall, L. monocytogenes was detected in 145 on 8716 of raw milk samples, with a prevalence of 1.66% (95% C.I. 1.4%–1.7%). The prevalence ranged from 0.52% (95% C.I. 0.3%–0.9%) in 2012 to 2.7% (95% C.I. 2.0%–3.8%) in 2013, but no trend of increase was observed in four-years of investigation. The pathogen was detected from 2.2% (95% C.I. 1.9%–2.6%) of bulk tank milk and from 0.5% (95% C.I. 0.3%–0.8%) of milk for vending machine. A significative difference (p < 0.05) of the prevalence data was observed between data collected in two different regions of Northern Italy with an higher prevalence in Lombardy. In addition to the geographical area, the L. monocytogenes presence was influenced also by the seasonal period of collection samples, with peaks in spring and autumn. These results confirm the raw milk can be a source of foodborne illness outbreaks if consumed without sanitizing treatments, but the low prevalence and the low contamination levels (more than 80% of the contaminated samples contained <10 cfu ml^−l of L. monocytogenes) proving the hygienic quality of the milk produced in Northern Italy.     

单核细胞增生性李斯特菌毒力基因检测及DNA随机扩增多态性分型

为了解在昌平地区分离的单核细胞增生性李斯特菌（Lm）携带毒力基因的状况和DNA随机扩增多态性（RAPD）分型情况，采用聚合酶链反应（PCR）对28株加进行了溶血素基因（hfy）、与侵袭性有关的卸和prfA基因的测定及RAPD分型。结果3个毒力基因PCR全部呈阳性反应，两株无害加为阴性反应。用RAPD分型，28株加分为12型．A、B两型共9株菌全部来自某肉联厂；C、D两型共10株来自某肉鸡公司；另外9株加有8个RAPD型．分别来自熟肉制品及零售市场。此次实验发现昌平地区在不同时间、不同地点分离的加其RAPD型别变化较大。有多种型别的细菌存在。根据RAPD分型看出肉联厂与肉鸡公司可能存在着内部污染问题。     

北京市昌平区市售乳及乳制品中邻苯二甲酸酯类物质的调查分析

目的了解北京市昌平区市售乳及乳制品中邻苯二甲酸酯(phthalates esters,PAEs)类物质的污染情况,为加强食品安全监督管理提供依据。方法 2014～2015年期间,在昌平区各商场、超市、零售店、批发市场等流通领域抽取国内外不同品牌的乳及乳制品共220件。利用固相萃取-气相色谱-质谱法(gas chromatography-mass spectrometry,GC-MS)测定16种邻苯二甲酸酯类化合物浓度。结果采集的220件样品中,共有206件样品检测出邻苯二甲酸酯类物质,总检出率为93.64%;其中邻苯二甲酸二异丁酯(diisobutyl phthalate,DIBP)、邻苯二甲酸二正丁酯(dibutyl phthalate,DBP)、邻苯二甲酸(2-乙基已基)酯(bis(2-ethylhexyl)phthalate,DEHP)和邻苯二甲酸丁基苄酯(butyl benzyl phthalate,BBP)的检出率分别为91.82%、91.82%、6.82%和1.82%,4类PAEs的最高检出浓度分别为0.085、0.287、0.204、0.151μg/g。结论在2014～2015年期间,昌平区市售乳及乳制品中PAEs检出率较高,应重视食品包装材料对食品的污染,定期开展监测工作。     

Low-Density Lipoprotein Cholesterol/High-Density Lipoprotein Cholesterol Ratio and Carotid Intima-Media Thickness: A Cohort Study in China

Low-density lipoprotein cholesterol to high-density lipoprotein cholesterol (LDL-C/HDL-C) ratio may carry additional information and has been suggested as a better predictor for atherosclerosis progression and cardiovascular disease (CVD) than LDL-C and HDL-C alone. Therefore, we aim to explore the association between LDL-C/HDL-C ratio and high carotid intima-media thickness (CIMT) risk in a large Cohort in Beijing, China. This cohort study included 13,612 adults without high CIMT at first entry and who attended the baseline examination and at least one follow-up annual examination between 2009 and 2016. We used multivariable Cox regression to estimate hazard ratios (HR) with their 95% confidence intervals (CI) for the association between LDL-C/HDL-C ratio and risk of high CIMT. During 37,912 person-years of follow-up, 1996 (1268 men and 728 women) developed high CIMT. Compared with the first quartile of LDL-C/HDL-C ratio, the risk of high CIMT was significantly increased for the fourth quartile of LDL-C/HDL-C ratio (HR = 1.51, 95% CI: 1.29–1.78). We observed a significant association between LDL-C/HDL-C ratio and high CIMT risk comparing LDL-C/HDL-C ratio >2.78 with LDL-C/HDL-C ratio ≤2.78 and significant dose–response relationship between LDL-C/HDL-C ratio and risk of high CIMT. The restricted cubic spline showed a significant nonlinear association between LDL-C/HDL-C ratio and the risk of high CIMT (p_{non-linearity} = 0.009). We identify a significant association between LDL-C/HDL-C ratio and the risk of high CIMT in the Chinese Cohort study. Future studies are needed to evaluate the effectiveness of reducing LDL-C/HDL-C ratio treatment on the development of high CIMT.