Detection of noroviruses in foods: a study on virus extraction procedures in foods implicated in outbreaks of human gastroenteritis

Disease outbreaks in which foods are epidemiologically implicated as the common source are frequently reported. Noroviruses and enteric hepatitis A viruses are among the most prevalent causative agents of foodborne diseases. However, the detection of these viruses in foods other than shellfish is often time-consuming and unsuccessful. In this study, three virus concentration methods were compared: polyethylene glycol (PEG) plus NaCl, ultracentrifugation, and ultrafiltration. Two RNA extraction methods, TRIzol and RNeasy Mini Kit (Qiagen), were compared for detection of viruses in whipped cream and lettuce (as representatives of the dairy and vegetable-fruit food groups, respectively). A seeding experiment with canine calicivirus was conducted to determine the efficiency of each virus extraction procedure. The PEG-NaCl-TRIzol method was most efficient for the detection of viruses in whipped cream and the ultracentrifugation-RNeasy-Mini Kit procedure was best for detection on lettuce. Based on the seeding experiments, food items implicated in norovirus-associated gastroenteritis outbreaks were subjected to the optimal procedure for a specific composition and matrix. No noroviruses were detected in the implicated food items, possibly because the concentration of virus on the food item was too low or because of the presence of inhibitory factors. For each food group, a specific procedure is optimal. Inhibitory factors should be controlled in these procedures because they influence virus detection in food.     

一起副溶血性弧菌食物中毒分离株的特征分析

目的 分析2017年广州市一起副溶血性弧菌食物中毒分离株的特征.方法 采用血清型鉴定,药敏实验,毒力基因(tdh、trh、tlh)、toxRS/new基因、orf8基因的聚合酶链式反应(PCR)检测,脉冲场凝胶电泳(PFGE)和多位点序列分型(MLST)进行分析.结果 14株副溶血性弧菌血清型鉴定为O8∶K21,药敏试...     

Detection of noroviruses in shellfish in the Netherlands

Shellfish from oyster farms in the Netherlands and imported from other European countries were examined for viral contamination. A method that allows sequence matching between noroviruses from human cases and shellfish was used. The samples of shellfish (n = 42) were analyzed using a semi-nested RT-PCR that had been optimized for detection of norovirus in shellfish (SR primer sets). In addition, a different genome region was targeted using a second primer set which is routinely used for diagnosis of norovirus infection in humans (JV12Y/JV13I). To improve the detection limit for this RT-PCR a semi-nested test format was developed (NV primer sets). One of 21 oyster samples (4.8%) from Dutch farms was norovirus positive, whereas norovirus was detected in 1 out of 8 oyster samples (12.5%) and 5 out of 13 mussel samples (38.5%) collected directly after importation in the Netherlands. RNA from samples associated with an outbreak of gastro-enteritis in the Netherlands in 2001 was re-analyzed using the NV primer sets. At least one identical sequence (142/142 nt) was found in three fecal and in two oyster samples related to this outbreak. Further surveillance of norovirus by detection and typing of viruses from patients with gastroenteritis and shellfish is warranted to clarify the causes of future outbreaks.     

武汉市某高校诺如病毒引起的食源性胃肠炎暴发

目的 分析2021年12月武汉某高校一起由诺如病毒引起的食源性胃肠炎暴发的流行病学因素,为制定防控措施提供科学依据。方法 开展现场流行病学调查,采用描述性流行病学方法、病例对照研究方法对导致事件发生的危险因素进行分析,并采集病例直肠拭子及环境样本进行病原学检测。结果 病例共139例,患病率为0.43%,临床症状主要为恶心、呕吐、腹泻。食用H街卤菜是危险暴露因素[比值比(OR)=15.96,95%置信区间(95%CI):2.32～383.95]。29名病例及5名从业人员检出诺如病毒GⅡ型。结论 此次事件为一起由诺如病毒GⅡ型引起的食源性胃肠炎暴发。在诺如病毒感染高发季节,应继续加强对学校及食品从业人员的诺如病毒感染监测,积极开展食品卫生方面的健康教育,预防肠道病原体感染暴发发生。     

一起布坦坦沙门氏菌引起的食物中毒

2002年1月9日，一熟肉摊贩销售的猪肉引起10人食物中毒，潜伏期5～25h，主要症状为腹痛（10人），腹泻（8人），发热（8人），恶心（8人），从销售剩余食物和病人剩余食物及病人的大便中检出布坦坦沙门氏菌，病人（6人）发病初期血清布坦坦沙门氏菌抗体滴度均为1：20。发病2周后2人1：80，4人1：320和1人1：640。根据流行病学调查，临床诊断和实验室鉴定结果，依照WS/T13-1996《沙门氏菌食物中毒诊断标准及处理原则》，确定这是一起布坦坦沙门氏菌的食物中毒，这起食物中毒提示必须加强食品零售摊贩的卫生管理。     

Detection and enumeration of Salmonella enteritidis in homemade ice cream associated with an outbreak: comparison of conventional and real-time PCR methods

Salmonellosis caused by Salmonella Enteritidis (SE) is a significant cause of foodborne illnesses in the United States. Consumption of undercooked eggs and egg-containing products has been the primary risk factor for the disease. The importance of the bacterial enumeration technique has been enormously stressed because of the quantitative risk analysis of SE in shell eggs. Traditional enumeration methods mainly depend on slow and tedious most-probable-number (MPN) methods. Therefore, specific, sensitive, and rapid methods for SE quantitation are needed to collect sufficient data for risk assessment and food safety policy development. We previously developed a real-time quantitative PCR assay for the direct detection and enumeration of SE and, in this study, applied it to naturally contaminated ice cream samples with and without enrichment. The detection limit of the real-time PCR assay was determined with artificially inoculated ice cream. When applied to the direct detection and quantification of SE in ice cream, the real-time PCR assay was as sensitive as the conventional plate count method in frequency of detection. However, populations of SE derived from real-time quantitative PCR were approximately 1 log higher than provided by MPN and CFU values obtained by conventional culture methods. The detection and enumeration of SE in naturally contaminated ice cream can be completed in 3 h by this real-time PCR method, whereas the cultural enrichment method requires 5 to 7 days. A commercial immunoassay for the specific detection of SE was also included in the study. The real-time PCR assay proved to be a valuable tool that may be useful to the food industry in monitoring its processes to improve product quality and safety.     

Detection of GI and GII noroviruses in drinking water and vegetables using filtration and real-time RT-PCR

The purpose of the study was to provide a rapid and sensitive method for detecting NoV GI and NoV GII in drinking water and vegetables. The method is based on viral concentration by microporous membrane adsorption method before RNA extraction and real-time RT-PCR amplification. Then water and vegetable samples which artificially contaminated with NoV GI and GII stool samples were used to determine the mean virus recoveries and the method sensitivity. The method showed the detection limit of NoV GI was 4.13 × 10² copies/500 mL for drinking water and 4.13 × 10³ copies/15 g for lettuce and coriander. The detection limit of NoV GII was 2.94 × 10¹ copies/500 mL for distilled water, 2.94 × 10² copies/500 mL for Mountain spring water and mineral water, and 2.94 × 10³ copies/15 g for lettuce and coriander. The method described provides a valuable tool for monitoring the potential public health risks associated with noroviruses contamination in drinking water and vegetables.     

An international outbreak of salmonellosis associated with raw almonds contaminated with a rare phage type of Salmonella enteritidis

During the winter of 2000 to 2001, an outbreak due to Salmonella Enteritidis (SE) phage type 30 (PT30), a rare strain, was detected in Canada. The ensuing investigation involved Canadian and American public health and food regulatory agencies and an academic research laboratory. Enhanced laboratory surveillance, including phage typing and pulsed-field gel electrophoresis, was used to identify cases. Case questionnaires were administered to collect information about food and environmental exposures. A case-control study with 16 matched case-control pairs was conducted to test the hypothesis of an association between raw whole almond consumption and infection. Almond samples were collected from case homes, retail outlets, and the implicated processor, and environmental samples were collected from processing equipment and associated farms for microbiological testing. One hundred sixty-eight laboratory-confirmed cases of SE PT30 infection (157 in Canada, 11 in the United States) were identified between October 2000 and July 2001. The case-control study identified raw whole almonds as the source of infection (odds ration, 21.1; 95% confidence interval, 3.6 to infinity). SE PT30 was detected in raw whole natural almonds collected from home, retail, distribution, and warehouse sources and from environmental swabs of processing equipment and associated farmers' orchards. The frequent and prolonged recovery of this specific organism from a large agricultural area was an unexpected finding and may indicate significant diffuse contamination on these farms. Identification of almonds as the source of a foodborne outbreak is a previously undocumented finding, leading to a North American recall of this product and a review of current industry practices.     

Osmotic dehydration of raspberries with vacuum pretreatment followed by microwave-vacuum drying

Defrozen raspberries were osmotically dehydrated in sucrose solution initially at low pressure (1.33 kPa for 8 min), and then at ambient pressure (4 h). Moisture decreased from 84% to 49% (wet basis), and almost one half of water removal occurred at the vacuum period. Two different transport coefficients were obtained: 19.9 × 10⁻¹⁰ m²/s for transport of water under vacuum, and 3.2 × 10⁻¹⁰ m²/s for water transport at atmospheric pressure. Losses of vitamin C were high (80%) and reutilization of sucrose solution is suggested. Osmotically dried raspberries were microwave-vacuum dried (1.33 kPa for 40 min) under on–off temperature control by varying microwave settings. An undamaged dried product (7.8% wet basis) of high quality (color, taste, structure) was obtained.     

Seasonal and tissue distribution of Laribacter hongkongensis, a novel bacterium associated with gastroenteritis, in retail freshwater fish in Hong Kong

Laribacter hongkongensis, a recently discovered bacterium associated with community-acquired gastroenteritis, has been found in the intestines of freshwater fish. To better understand the epidemiology and ecology of the bacterium, we carried out a surveillance study to investigate possible seasonal variation in the recovery of L. hongkongensis and its distribution in various organs in retail freshwater fish in Hong Kong. Forty whole freshwater fish of two species (20 grass carps and 20 bighead carps), and intestines from 120 grass carps were sampled during a one-year period. L. hongkongensis was isolated from 11 (55%) of the 20 grass carps and 6 (30%) of the 20 bighead carps; and the intestines of 49 (41%) of 120 grass carps. Seasonal variation in the recovery of L. hongkongensis from both whole fish and intestines was observed, with higher isolation rates in spring and summer than in fall and winter. There was also positive correlation between temperature and the isolation rates. When L. hongkongensis was cultured in vitro at different temperatures, shorter lag time and higher growth rate were observed at higher temperatures, with 37 degrees C being optimal among the tested temperatures. L. hongkongensis was commonly found in the gills, stomachs and intestines in both grass carps and bighead carps, and on the skin surface of one fish, but not in other organs. Proper handling of freshwater fish for cooking, especially the gills and gut, is recommended to prevent acquisition of L. hongkongensis, and other freshwater fish related infections.     

Odour thresholds of some important aroma compounds in raspberries

Summary The odour thresholds of ten aroma compounds in raspberries, including the character impact compound 4-(4-hydroxyphenyl)-butan-2-one (raspberry ketone), were determined using a modified duo-trio test. These thresholds were compared with the concentrations of the aroma compounds in ten raspberry varieties to show which aroma compounds were the most important in contributing to the flavour.

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Geruchschwellen einiger wichtiger Aromastoffe der Himbeeren

Zusammenfassung Die Geruchschwellen von 10 Aromastoffen der Himbeeren, einschließlich der charakteristischen Verbindung 4-(4-Hydroxyphenyl)-butan-2-on (Himbeerketon), wurden mit einem modifizierten Duo-trio-test bestimmt. Diese Schwellen wurden mit den Konzentrationen der Aromastoffe in 10 Himbeersorten verglichen, um zu zeigen, welche Aromastoffe am wichtigsten sind.

     

一起蜡样芽孢杆菌污染学生营养午餐造成食物中毒的调查

2000年10月26日一学生营养餐生产生企业向17所中小学供应营养午餐，其中5所小学同时发生食物中毒，5所小学1658名学生进食，84人发病，发病率为1.5%，主要症状为腹痛，腹泻，潜伏期6～22h，中位数17h，根据流行病学调查，临床表现，实验室检验结果分析，认为这是一起由Ⅱ型蜡样芽孢杆菌引起的细菌性食物中毒，可疑食品为加到26日午餐中的25日剩下的土豆烧牛肉和烩豆腐，经对症治疗后，全部病人症状绘解，预后良好，无危重病人和死亡病例。     

秦皇岛市一起由副溶血性弧菌引起的食源性疾病暴发事件的检测和溯源分析

目的 对一起食源性疾病暴发事件检出的目标菌进行血清分型、毒力基因、耐药性检测及分子分型检测,明确导致食源性疾病暴发事件的致病菌及可能性溯源.方法 采集病例腹泻便及可疑环境样本进行致病菌的检测,对分离出来的可疑致病菌进行生化鉴定、血清分型、毒力基因检测及脉冲场凝胶电泳(pulsed field gel electroph...     

A prolonged outbreak of Salmonella Montevideo infections associated with multiple locations of a restaurant chain in Phoenix, Arizona, 2008

An outbreak of Salmonella serotype Montevideo infections associated with multiple locations of restaurant chain A in Phoenix, AZ, was identified in July 2008. One infected individual reported eating at a chain A catered luncheon where others fell ill; we conducted a cohort study among attendees to identify the vehicle. Food and environmental samples collected at six chain A locations were cultured for Salmonella. Restaurant inspection results were compared among 18 chain A locations. Routine surveillance identified 58 Arizona residents infected with the outbreak strain. Three chain A locations, one of which catered the luncheon, were named by two or more case patients as a meal source in the week prior to illness onset. In the cohort study of luncheon attendees, 30 reported illness, 10 of which were later culture confirmed. Illness was reported by 30 (61%) of 49 attendees who ate chicken and by 0 of 7 who did not. The outbreak strain was isolated from two of these three locations from uncooked chicken in marinade, chopped cilantro, and a cutting board dedicated to cutting cooked chicken. Raw chicken, contaminated before arrival at the restaurant, was the apparent source of this outbreak. The three locations where two or more case patients ate had critical violations upon routine inspection, while 15 other locations received none. Poor hygiene likely led to cross-contamination of food and work areas. This outbreak supports the potential use of inspections in identifying restaurants at high risk of outbreaks and the need to reduce contamination of raw products at the source and prevent cross-contamination at the point of service.