2019年冻鱼糜制品中食源性致病菌污染状况分析

目的 了解冻鱼糜制品中食源性致病菌污染状况。方法 从全国范围内采集冻鱼糜制品4 516份，按照食品安全国家标准《食品微生物学检验》相应标准的规定，对样品中单核细胞增生李斯特菌、副溶血性弧菌、小肠结肠炎耶尔森氏菌、致泻大肠埃希菌进行检验。结果 单核细胞增生李斯特菌检出率6.02%（272/4 516），副溶血性弧菌检出率0.84%（38/4 516），小肠结肠炎耶尔森氏菌检出率0.84%（38/4 516），致泻大肠埃希菌检出率0.91%（41/4 516）。单核细胞增生李斯特菌的污染在4种食源性致病菌中较为突出，且不同产地的样品中单核细胞增生李斯特菌的污染差异较大。除副溶血性弧菌以外，其余3种食源性致病菌在散装样品中的检出率均高于预包装样品。结论 市售冻鱼糜制品存在致病菌污染，需要关注其健康风险。     

六类食品中致病性细菌检测

为了解昌平区细菌对食品污染的特点，2004年采集6类305件食品，按照GB／T4789－2003食品微生物检验标准进行沙门菌、金黄色葡萄球菌、副溶血性弧菌、单核细胞增生性李斯特菌、0157：H7大肠杆菌5种致病菌检测。菌株鉴定应用API细菌鉴定系统，肠毒素检测用minVIDAS测试系统，单核细胞增生性李斯特菌毒力基因测定采用聚合酶链反应（PCR）。金黄色葡萄球菌检出率为16．07％，其中生肉、生牛奶、生食水产品检出率比较高，分别为25％、16．98％、27．27％；散装熟肉制品、乳制品也有检出，分别为4.29％、5％。在检出的49株金黄色葡萄球菌菌株中有31株产生肠毒素，占63．26％，其中生、熟肉类肠毒素阳性25株；从奶类、生食水产品中各检出3株。单核细胞增生性李斯特菌检出34株，检出率为11．15％，其中生肉检出率高达20％，其次为散装熟肉制品（8．57％）；另外从淡水鱼中检出4株单核细胞增生性李斯特菌。28株单核细胞增生性李斯特菌毒力基因（hly、iap、prfA）检测全部阳性。生肉中检出一株肠炎沙门菌。未检出O157：H7大肠杆菌、副溶血性弧菌。昌平地区金黄色葡萄球菌和单核细胞增生李斯特菌对食物的污染比较严重，生食品与加工后食品的检出率差异有显著性。     

江干区部分食品中单增李斯特菌污染状况分析

目的了解江干区食品中单核细胞增生性李斯特菌污染状况。方法参考国标方法,采用进口显色培养基,对4类食品进行单核细胞增生性李斯特菌分离,生化及血清型鉴定。结果109份样品共检出单核细胞增生性李斯特菌15株,总检出率为13.8%;生肉类、生食果蔬类检出率分别为36.8%、5.9%,熟肉制品和水产品中未检出。15株单核细胞增生性李斯特菌分属2个血清型,1/2b血清型占73.3%,1/2a血清型占26.7%。结论江干区食品中存在单核细胞增生性李斯特菌的污染,特别是生肉。     

生肉中单核细胞增生性李斯特菌的分离与鉴定

目的了解哈尔滨市售生肉中单核细胞增生性李斯特菌的污染状况。方法将显色培养基法、API试剂条法和PCR法联合应用对哈尔滨市售128份生肉进行单核细胞增生性李斯特菌的分离鉴定。结果共分离出单核细胞增生性李斯特菌18株,检出率为14.06%。其中生猪肉检出率最高,达20.00%。结论哈尔滨市售生肉中单核细胞增生性李斯特菌污染状况比较严重,应引起有关部门的重视,加强管理和监测。     

部分市售农副产品李斯特菌污染情况调查及毒力基因检测

目的了解上海市闵行区农贸市场食品中李斯特菌的污染情况及其毒力基因的携带情况。方法按国标方法GB/T4789.30—2008《食品卫生微生物学检验单核细胞增生李斯特氏菌检验》,采用科玛嘉显色培养基,对食品进行李斯特菌的分离、API试剂条进行生化鉴定,PCR扩增进行hly、prfA、plcB、actA、inlA和iap6种毒力基因的检测。结果320份样品中共检出李斯特菌36株,其中单核细胞增生李斯特菌10株;英诺克李斯特菌23株,其余3株。10株单核细胞增生李斯特菌hly、prfA、plcB、iap、inlA、actA6种毒力基因携带率分别为100%、100%、100%、100%、100%和0,即10株菌株actA基因全部缺失。结论本地区农贸市场食品存在李斯特菌的污染,生肉禽类食品中李斯特菌污染比较严重,应加强监督管理;单核细胞增生李斯特菌菌株actA毒力基因均表现为缺失,是否为本地区特性,还有待研究。     

福建省2000年～2003年食品中单核细胞增生李斯特菌的监测与分析

为系统了解福建省食品中单核细胞增生李斯特菌的污染状况、分布特征以及血清型别，为评价和预警我省食品污染状况和制定相关食品卫生政策提供可靠的基础数据，根据福建省的不同地理位置和经济状况，选择福州、泉州、龙岩和尤溪4个市县为监测点，在夏季和冬季随机采集农贸市场的4大类样品。样品LB增菌后，采用科玛嘉单核细胞增生李斯特菌显色平板分离，做VITEK32全自动微生物鉴定系统和Listeria monocytogenes API试剂条生化试验、溶血试验、小鼠毒力试验和血清学试验。2000年～2003年对生肉、熟肉、水产品和生牛奶4大类共1369份食品进行检测，单核细胞增生李斯特菌的总检出率为6．14％。不同种类食品的阳性率高低不一，阳性率最高为生肉(12．44％)，水产品和生牛奶中均未检出。生肉类中阳性率最高为冻鸡肉(38.46％)，鲜鸡肉中未检出。4个市县的检出率呈地区性差异，幅度介于7．55％～5．20％之间。夏季和冬季的检出率差异无显性。30株单核细胞增生李斯特菌的血清型别以1／2a型为主。监测结果显示福建省市售生(冻)畜禽肉存在着不同程度的单核细胞增生李斯特菌污染，应加强畜、禽类屠宰、运输、加工过程的卫生管理和监测，提出预防单核细胞增生李斯特菌食物中毒和加强宣传教育的措施，减少食源性疾病的发生。     

广西单核细胞增生李斯特菌的流行率、毒力特征和分子分型研究

目的 比较广西不同种类食品中单核细胞增生李斯特菌（以下简称单增李斯特菌）的流行情况、毒力特征和分子分型特征，更好地了解单增李斯特菌的遗传特点及其传播的潜力。方法 对来自2002—2020年的210株单增李斯特菌进行全基因组测序（WGS），分析其序列分型（ST）、克隆群（CC）型及毒力基因。结果 2002—2020年广西53.8%单增李斯特菌分离株来源于肉与肉制品，59.0%分离株来自于谱系Ⅱ，优势ST型为ST8和ST9。79.4%菌株携带LIPI-1基因（hly、prfA、plcA、plcB、mpl、actA），83.7%菌株携带LIPI-2基因（inlC、inlF、inlJ、inlK）。17.6%菌株携带LIPI-3基因（llsA、llsB、llsD、llsG、llsH、llsP、llsX、llsY）。结论 肉与肉制品是广西单增李斯特菌检出率最高的食品类型，分子分型结果证实了单增李斯特菌种群具有高度的遗传多样性，WGS的高分辨力可用于监测食源性单增李斯特菌病的暴发。毒力基因的分布表明广西单增李斯特菌存在不同程度毒力基因的缺失，应警惕高致病性的菌株引起的食源性暴发事件。     

食源性单增李斯特菌与英诺克李斯特菌基因组特征比较

目的 通过全基因组测序对甘肃省市售食品中分离的单增李斯特菌和英诺克李斯特菌基因组特征进行比较分析。方法 收集2021—2022年甘肃省市售食品中分离的25株单增李斯特菌和7株英诺克李斯特菌作为研究对象,对菌株进行全基因组测序,分析其系统发育谱系、克隆复合群（CC）、序列型（ST）、毒力基因、抗性基因及泛基因组。结果 32株李斯特菌分属单增李斯特菌谱系Ⅰ和Ⅱ及英诺克李斯特菌3个群,单增李斯特菌分为10个亚群,英诺克李斯特菌分为5个亚群,与CC型保持一致,核心基因组多位点序列分型能将各谱系中不同CC型的菌株明显分开,谱系Ⅰ与英诺克李斯特菌的进化关系更近。25株单增李斯特菌均携带李斯特菌毒力岛LIPI-1和内化素基因,不携带LIPI-3,有2株ST87型菌株携带LIPI-4;7株英诺克李斯特菌均不携带LIPI-1和内化素基因,均携带LIPI-4,有5株菌携带LIPI-3。单增李斯特菌有16株携带SSI-1、3株携带SSI-2,7株英诺克李斯特菌均不携带SSI-1,有6株携带SSI-2。李斯特菌的泛基因组大小随着测序基因组数目的增加呈现线性增多,25株单增李斯特菌当菌株数量达到15后核心基因数目稳定在2 272个,占泛基因组基因数目的46.2%,25株单增李斯特菌和7株英诺克李斯特菌共同的核心基因1 487个,当菌株数量达到10后数目趋于稳定。结论 核心基因组多位点序列分型可将不同谱系不同克隆复合群的李斯特菌进行区分,英诺克李斯特菌与单增李斯特菌生化特性相似与其亲缘关系相近有关,致病性差异与英诺克李斯特菌缺失单增李斯特菌特有的毒力基因相关。     

江西省首起中式凉拌菜引起一例孕妇李斯特菌病的溯源研究

目的 对江西省首起中式凉拌菜引起一例孕妇李斯特菌病进行溯源分析。方法 采用描述性研究方法对李斯特菌病患者开展流行病学调查，采用临床检测方法和国家标准GB 4789.30—2016方法对血液、食品样品中的单核细胞增生性李斯特菌进行分离，并用生化、质谱方法对分离的菌株进行鉴定，菌株的分型和溯源分析使用脉冲场凝胶电泳、全基因组测序方法。结果 流调结果显示，患者症状以发热为主，新生儿无感染，有每周进食一次中式凉拌菜的习惯。患者血培养鉴定结果为单核细胞增生性李斯特菌，现场对患者家进行的环境样本采样未检出单核细胞增生性李斯特菌，采集患者常去的熟食店销售的2份凉拌菜检出了该细菌。PFGE电泳分型显示患者分离株与食品分离株分型结果一致，全基因组测序结果菌株均为ST1型。结论 中式凉拌菜存在引起孕妇李斯特菌病的风险，应加强监测，有关部门应加强对相关餐饮店的监管。     

食品中单核细胞增生李斯特菌株的分离及聚合酶链式反应鉴定

目的 建立单核细胞增生李斯特菌的聚合酶链式反应(PCR)检测方法,了解市售食品中单核细胞增生李斯特菌的污染情况.方法 采集成都市市售生畜肉、生禽肉、熟肉制品、水产品、生食蔬菜以及其他熟食等食品样品共135份,采用李氏增菌肉汤(LB1,LB2)进行初增菌,应用选择性分离培养基PALCAM和在TSA-YE平板上进行分离,利用单增李斯特显色平板进行鉴定;根据李斯特菌的特异性基因iap基因设计引物,采用PCR方法检测所有分离的李斯特菌株;根据单增李斯特菌的特异性基因hly基因和prfA基因设计引物检测单核细胞增生李斯特菌株.结果 135份样品中共检出李斯特菌17株,检出率为12.6％;其中单核细胞增生李斯特菌4株,检出率为3.0％.结论 本研究建立的PCR方法具有特异性,本市市售食品不同程度受到李斯特菌的污染.     

Arsenic content of some edible mushroom species

The arsenic contents of 162 fruit body samples of 37 common edible mushroom taxa were analyzed. The samples were gathered from different habitats of Hungary (mainly from mountains) between 1984 and 1999. The arsenic content of the samples was measured by the inductively coupled plasma spectrometry method. Very low [lower than 0.05 mg/kg dry matter (DM)] concentrations were found in the samples of 13 taxa, while higher (or very high) contents were quantified in other common taxa (the highest arsenic content was recorded in the fruit body of Laccaria amethysthea at 146.9 mg/kg DM). The species of eight genera (Agaricus, Calvatia, Collybia, Laccaria, Langermannia, Lepista, Lycoperdon, Macrolepiota) belong to the so-called accumulating taxa, and this tendency is evident on all habitats. This arsenic accumulation capability is found in two orders of Basidiomycetes (Agaricales and Gasteromycetales), which is to say this phenomenon occurs in the families Agaricaceae, Tricholomataceae and Gasteromycetaceae. The accumulating taxa found all have a saprotrophic type of nutrition; arsenic accumulation is not detectable in xilophagous or in mycorrhizal species. The consumption of the accumulating species found has only a low toxicological risk for three reasons: the consumed fresh fruit bodies contain about a tenfold lower arsenic level than the dried ones, the majority of arsenic occurs not in poisonous inorganic, but in less dangerous (or not poisonous) organic forms, and the frequency of consumption is low.     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Cloning and expression analysis of two catalase genes from Aspergillus oryzae

Fungi contain distinct genes encoding the same class of enzyme that are differentially regulated according to conditions. We cloned two catalase genes, catA and catB, from Aspergillus oryzae. The catA gene predicts a 747-amino-acid polypeptide sharing 81% identity with Aspergillus fumigatus catalase (catA) and 77% with Aspergillus nidulans catalase (catA). The catB gene predicts a 725-amino-acid polypeptide sharing 82% identity with A. fumigatus catalase (catB) and 75% with A. nidulans catalase (catB). However, the catA and catB genes share little homology (41%) with one another, suggesting that each gene belongs to a distinct gene family. Overexpression studies demonstrated that both genes encode a functional catalase. Promoter assays indicated that the catA gene is developmentally regulated as it was preferentially expressed in solid-state cultures undergoing sporulation. However, its expression was not affected by hydrogen peroxide treatment. Conversely, the catB gene was highly expressed under all culture conditions tested, and it was induced by hydrogen peroxide treatment. These results suggest that the catB gene may be mainly used for detoxification of oxidative stress while the catA gene may have another role such as chaperoning proteins in the spore.     

Assessment of the microbiological safety of salad vegetables and sauces from kebab take-away restaurants in the United Kingdom

The purpose of this study was to establish the microbiological safety of salad vegetables and sauces served in kebab take-away restaurants. Comparison with published microbiological guidelines revealed that 4.7% of 1213 salad vegetable samples were of unsatisfactory microbiological quality due to Escherichia coli and/or Staphylococcus aureus levels at ≥10² cfu g⁻¹. Another 0.3% of salad samples were of unacceptable quality due to S. aureus at ≥10⁴ cfu g⁻¹ (2 samples) or the presence of Salmonella Kentucky (1 sample). Cucumber was the most contaminated salad vegetable with regards to unsatisfactory levels of E. coli (6.0%) or S. aureus (4.5%). Five percent of 1208 sauce samples were of unsatisfactory microbiological quality due to E. coli, S. aureus at ≥10² cfu g⁻¹ and/or Bacillus cereus and other Bacillus spp. at ≥10⁴ cfu g⁻¹. A further 0.6% of sauce samples were of unacceptable quality due to Bacillus spp. (Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis) at ≥10⁵ cfu g⁻¹ or the presence of Salmonella Agbeni (1 sample). More samples of chilli sauce (8.7%) were of unsatisfactory or unacceptable microbiological quality than any other sauce types. The results emphasize the need for good hygiene practices in kebab take-away restaurants handling these types of ready-to-eat products.