2004-2007年肇庆市食品中食源性致病菌监测与分析

目的了解肇庆市食品中食源性致病菌的污染状况和污染水平,初步确定高危食品的种类,为食源性疾病的监测提供科学的依据。方法按全国食品污染物监测网的工作手册,2004-2007年采集4个监测点的5大类食品(生肉、熟肉、水产品、生吃水产品和生吃蔬菜)共计325份,对沙门菌、单核细胞增生李斯特菌、大肠杆菌O157∶H7和副溶血性弧菌4种食源性致病菌进行监测分析。结果325份食品样品中,检出致病菌27株(8.31%)。其中沙门菌16株(4.92%),单核细胞增生李斯特菌10株(3.08%),大肠杆菌O157∶H7未检出,80份水产品中检出副溶血性弧菌1株(1.25%)。生肉的污染情况最为严重,检出率为11.35%,其次是熟肉,检出率为9.68%;水产品的检出率为5.45%,生食水产品的检出率为4.00%,生食蔬菜的检出率为2.56%。结论沙门菌和单核细胞增生李斯特菌对肇庆市食品的污染普遍存在。生肉、熟肉的污染尤为严重,是重要的高危食品。     

2005-2007年宝鸡市食源性致病菌污染监测与分析

目的了解宝鸡市食源性致病菌污染状况。方法按照GB/T 4789—2003食品微生物检验标准方法检测。结果2005-2007年共对302份食品进行食源性致病菌污染监测,检出致病菌86株,检出率为28.5%,其中单增李斯特菌52株,检出率为17.2%,副溶血性弧菌24株,检出率为38.1%,沙门菌8株,检出率为2.6%,出血性大肠埃希菌O157∶H72株,检出率为0.7%。5类食品中鲜冻水产、生畜禽肉、速冻食品致病菌检出率较高,分别为55.6%、30.7%、25.0%%,熟肉制品、生食蔬菜中也有检出,分别为7.8%、7.3%。结论鲜冻水产、生畜禽肉、速冻食品是食源性致病菌污染的主要食品,存在食物中毒隐患,应引起足够重视。     

Viability of multi-strain mixtures of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 inoculated into the batter or onto the surface of a soudjouk-style fermented semi-dry sausage

The fate of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 were separately monitored both in and on soudjouk. Fermentation and drying alone reduced numbers of L. monocytogenes by 0.07 and 0.74 log₁₀ CFU/g for sausages fermented to pH 5.3 and 4.8, respectively, whereas numbers of S. typhimurium and E. coli O157:H7 were reduced by 1.52 and 3.51 log₁₀ CFU/g and 0.03 and 1.11 log₁₀ CFU/g, respectively. When sausages fermented to pH 5.3 or 4.8 were stored at 4, 10, or 21 °C, numbers of L. monocytogenes, S. typhimurium, and E. coli O157:H7 decreased by an additional 0.08–1.80, 0.88–3.74, and 0.68–3.17 log₁₀ CFU/g, respectively, within 30 days. Storage for 90 days of commercially manufactured soudjouk that was sliced and then surface inoculated with L. monocytogenes, S. typhimurium, and E. coli O157:H7 generated average D-values of ca. 10.1, 7.6, and 5.9 days at 4 °C; 6.4, 4.3, and 2.9 days at 10 °C; 1.4, 0.9, and 1.6 days at 21 °C; and 0.9, 1.4, and 0.25 days at 30 °C. Overall, fermentation to pH 4.8 and storage at 21 °C was the most effective treatment for reducing numbers of L. monocytogenes (2.54 log₁₀ CFU/g reduction), S. typhimurium (5.23 log₁₀ CFU/g reduction), and E. coli O157:H7 (3.48 log₁₀ CFU/g reduction). In summary, soudjouk-style sausage does not provide a favorable environment for outgrowth/survival of these three pathogens.     

Influence of biotic and abiotic factors on human pathogens in a finished compost

The role of indigenous microflora of a finished compost, defined NK12, on the growth suppression of pathogens under different moisture and temperature storages was investigated. Total count of mesophilic and thermophilic bacteria was evaluated by the most probable number method and growth of seeded Salmonella arizonae 3924 serogroup B and enteropathogenic Escherichia coli 84 M in NK12 at different moisture temperature conditions was monitored. Results on sterile and non-sterile NK12 were compared. In all tested experimental conditions, the NK12 indigenous microflora was stable and biologically active. S. arizonae 3924 and E. coli 84 M grew rapidly in sterilized NK12 at different moistures and storage temperatures, and their growth was suppressed in non-sterilized NK12. Pathogens inactivation was lower when compost was stored at 40% and 80% humidity and at 37 degrees C. Our results show that the major role in the pathogens suppression was played by the indigenous microflora of the finished compost, although physical factors too influenced the growth phenomenon.     

Growth and bacteriocin production by lactic acid bacteria in vegetable broth and their effectiveness at reducing Listeria monocytogenes in vitro and in fresh-cut lettuce

The fresh-cut fruit and vegetable industry is searching for alternatives to replace chemical treatments with biopreservative approaches that ensure the safety of the product and fulfil consumer preferences for minimally processed foods. In this study, the use of bacteriocins produced by lactic acid bacteria has been tested as a substitute for chemical disinfection of fresh-cut iceberg lettuce. First, the ability of several non-plant origin bacteriocinogenic strains (nisin Z(+), plantaricin C(+), lacticin 481(+), coagulin(+) or pediocin PA-1(+)) to grow in a lettuce extract at 4 degrees C, 10 degrees C and 32 degrees C was tested. All strains were able to grow, but bacteriocin production was predominantly detected at 32 degrees C. Addition of bacteriocinogenic supernatants (nisin(+), coagulin(+) and a nisin-coagulin(+) cocktail) to tryptic-soy agar plates inoculated with Listeria monocytogenes reduced Listeria counts by approximately 1-1.5 log units compared with the control plates without bacteriocin, after 48 h of storage at 4 degrees C. The effect of washing with bacteriocin-containing solutions on survival and proliferation of Listeria monocytogenes was also evaluated in fresh-cut lettuce packaged in macro-perforated polypropylene bags and stored for 7 days at 4 degrees C. Washing fresh-cut lettuce with these solutions decreased the viability of Listeria monocytogenes by 1.2-1.6 log units immediately after treatment, but, during storage at 4 degrees C, bacteriocin treatments only exerted minimal control over the growth of the pathogen. Natural microbiota were little affected by bacteriocins during storage.     

Preparation of antibody-conjugated gold nanoparticles

We here describe a method for the simple synthesis of gold nanoparticles (~ 10 nm in diameter) conjugated with antibody to E. coli O157:H7. Gold nanoparticles with pendant carboxylic acid and alcohol functional groups were synthesized and characterized using transmission electron microscopy (TEM) and infrared spectroscopy. These nanoparticles were then reacted with anti-E. coli O157:H7, using EDC coupling chemistry, and the product was characterized with X-ray photoelectron spectroscopy. Furthermore, binding of the antibody-gold conjugates to E. coli O157:H7 was demonstrated using transmission electron microscopy.     

原料奶中病原菌的调查及代表性病原菌的研究

对榨乳过程进行了采样分析,确定了原料奶中的主要致病菌为金黄色葡萄球菌,并分析了原料奶在不同温度储存时金黄色葡萄球菌的生长情况以及金黄色葡萄球菌在酸奶发酵和冷藏过程中的存活情况。研究发现,酸奶的低酸性环境并不能有效的抑制金黄色葡萄球菌的生长,所以为了确保产品的安全性,要对奶牛的乳房炎和隐性乳房炎进行有效防治,并严格控制榨乳的卫生条件及原料奶的储存温度。     

山东花生茎腐病病原菌研究

从山东省多地采集的花生茎腐病株上分离到15个茎腐病菌株,选取6个典型菌株,对病原菌进行形态特征、致病性、生物学特性研究。核糖体DNA-ITS序列分析表明,6个菌株的核糖体DNA-ITS序列同源性高达99％。根据病原菌的形态特征、核糖体DNA-ITS序列同源性比较,确认供试6个菌株为同一种病原菌,与Gen-Bank中可可毛色二孢属（Lasiodiplodia）（Diplodia的同物异名）的同源性高达99％以上。根据6个菌株的形态特征、致病性测定结果及生物学特性,并结合核糖体DNA-ITS序列分析,将山东花生茎腐病的病原鉴定为棉色二孢菌（Diplodia gossypina）。     

Efficacy of washing meat surfaces with 2% levulinic, acetic, or lactic acid for pathogen decontamination and residual growth inhibition

We compared spray washing at 55.4 °C with 2% levulinic acid to that with lactic or acetic acid for decontamination of pathogenic bacteria inoculated onto meat surfaces, and their residual protection against later growth of pathogenic bacteria. The model systems included Escherichia coli O157:H7 on beef plate, Salmonella on chicken skin and pork belly, and Listeria monocytogenes on turkey roll. In the decontamination studies, acid washes lowered recoverable numbers of pathogens by 0.6 to 1 log/cm(2) as compared to no-wash controls, and only lactic acid lowered the number of pathogens recovered as compared to the water wash. Washing with levulinic acid at 68.3 or 76.7 °C did not result in additional decontamination of E. coli. Acetic acid prevented residual growth of E. coli and L. monocytogenes, and it reduced numbers of Salmonella on chicken skin to below recoverable levels. Overall, levulinic acid did not provide as effective decontamination as lactic acid nor residual protection as acetic acid.     

Optimization of resuscitation-promoting broths for the revival of Vibrio parahaemolyticus from a viable but nonculturable state

Food Science and Biotechnology - This study was conducted to examine the effect of formulated resuscitation-promoting broths on the revival of viable but nonculturable Vibrio parahaemolyticus...