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.     

Effect of surface sites of TiO2 support on the formation of cobalt-support compound in Co/TiO2 catalysts

This study has addressed the effect of surface sites (as Ti⁴⁺ and Ti³⁺) of TiO₂ support on the formation of the cobalt-support compound on Co/TiO₂ catalyst. A 20% cobalt was prepared on each TiO₂ support having the different Ti⁴⁺/Ti³⁺ ratios covering on the surface (1.2, 1.3, 1.4, and 1.6). It can be concluded that the non-reducible compound as a Co-SCF preferred to form on the Co/TiO₂ catalyst when the most proportional site of surface TiO₂ became Ti⁴⁺. This is because the migration of cobalt cluster, which plays the significant role for creating Co-SCF, can be promoted by the increasing of Ti⁴⁺ sites resulting in the decrease of cobalt dispersion. The hyperfine patterns of ESR spectra demonstrated that the Co⁰(H_xTiO_y) was the simple chemical form of Co-SCF formed after standard reduction. Moreover, the structure of Co-SCF changed to be a higher non-uniform structure when the number of Ti⁴⁺ site on TiO₂ surface increased. The possible mechanism to form this compound has also been discussed.     

Reduction of Escherichia coli O157:H7 and Salmonella enteritidis on mung bean seeds and sprouts by slightly acidic electrolyzed water

High microbial populations on mung beans and its sprouts are the primary reason of a short shelf life of these products, and potentially present pathogens may cause human illness outbreak. The efficiency for inactivating Escherichia coli O157:H7 (E. coli O157:H7) and Salmonella enteritidis (S. enteritidis), which were artificially inoculated on mung bean seeds and sprouts, by means of slightly acidic electrolyzed water (SAEW, pH 5.0 to 6.5) generated through electrolysis of a mixture of NaCl and hydrochloric acid solution in a non-membrane electrolytic chamber, was evaluated at the different available chlorine concentrations (ACCs, 20–120 mg/l) and treatment time (3–15 min), respectively. The effect of SAEW treatment on the viability of seeds was also determined. Results indicate that the ACC had more significant effect on the bactericidal activity of SAEW for reducing both pathogens on the seeds and sprouts compared to treatment time (P < 0.05). The seeds and sprouts treated with SAEW at ACCs of 20 and 80 mg/l resulted in a reduction of 1.32–1.78 log₁₀ CFU/g and 3.32–4.24 log₁₀ CFU/g for E. coli, while 1.27–1.76 log₁₀ CFU/g and 3.12–4.19 log₁₀ CFU/g for S. enteritidis, respectively. The germination percentage of mung bean seeds was not significantly affected by the treatment of SAEW at an ACC of 20 mg/l for less than 10 min (P > 0.05). The finding of this study implies that SAEW with a near-neutral pH value and low available chlorine is an effective method to reduce foodborne pathogens on seeds and sprouts with less effects on the viability of seeds.     

纯净水中病毒三种富集方法的比较

目的 比较膜吸附法、膜吸附-PEG法和膜吸附-超滤法对纯净水中病毒的富集效果,并对优选的富集方法的实验条件进行比对,旨在寻找高效的方法,为其他水体中病毒富集检测提供技术借鉴。方法 本文以MS2噬菌体为目标病毒,制作高、低浓度水样,建立逆转录-荧光定量聚合酶链式反应(RT-qPCR)方法的标准曲线,进行定量检测。使用膜吸附法、膜吸附-PEG法和膜吸附-超滤法富集水样,并比较不同过滤膜、不同超滤管及两种核酸提取方法的回收率,选择最适方法。结果 膜吸附-超滤法、膜吸附-PEG法和膜吸附法回收率均值分别为19.80%±12.19%、12.71%±9.09%和9.05%±4.89%,各因素对回收率的影响顺序为:膜吸附-超滤法>膜吸附-PEG法>膜吸附法;高浓度>低浓度。混合纤维素酯膜的富集效果优于尼龙膜。100 K和50 K的超滤管富集效果无差异。硅胶离心柱法和磁珠法核酸提取效果无差异。结论 通过二次富集可提高富集效率,膜吸附-超滤法优于另两种方法,且其操作简单、耗时短、对设备依赖性低,易于推广。膜吸附-超滤法的实验条件仍可优化、完善,拓展其在不同水体和不同病毒富集中的应用。     

江苏省实施常见职业性放射性疾病诊断标准的调查

采取问卷调查方式,对江苏省内职业性放射性疾病诊断医师、放射工作人员、放射卫生监督人员开展问卷调查,评估5项常见职业性放射性疾病诊断标准在江苏省的实施情况。结果表明:(1)职业性放射性疾病诊断医师对标准的掌握率为61%～89.6%;参加培训率为59.7%～92.2%;标准应用率为62.3%～68.8%,其培训率和应用率显著高于放射卫生监督人员。(2)放射工作人员除《职业性放射性皮肤疾病诊断》的知晓率同放射卫生监督人员有明显差别外,其余标准知晓率两者无统计学差异。(3)放射卫生监督人员标准的培训率为3.2%～48.0%,显著低于职业性放射性疾病诊断医师和放射工作人员,差异有统计学意义。(4)放射工作人员对职业性放射性疾病认知情况的问题回答正确率为34.7%～89.7%,且医疗机构和非医疗机构无明显差别,放射工作人员对申请职业性放射性疾病提交材料的认知情况为73.6%～100%。(5)职业性放射性疾病诊断医师、放射工作人员、放射卫生监督人员对标准中部分条款的认可度尚可。     

液相色谱法测定油脂及其制品中苯并(a)芘含量

目的 建立液相色谱法测定油脂及其制品中苯并(a)芘的方法。方法 试样经过正己烷提取, 中性氧化铝或分子印迹小柱净化, C18色谱柱分离, 荧光检测器检测。结果 方法的线性范围为0.5~20 μg/L, 线性相关系数为0.9999, 最低定量浓度(the limit of quantity, LOQ)为0.5 μg/kg, 在0.5、5、15 μg/kg 3个添加水平下平均回收率为75.5%~93.8%, 相对标准偏差(relative standard deviation, RSD)为3.0%~9.6%。结论 该方法准确度与精密度满足GB/T 27404规定, 定量限满足GB 2762实施要求, 被用于修订GB/T 5009.27-2003为 GB 5009.27-2016。     

高效液相色谱法同时测定食品中10种合成着色剂

目的 建立一种高效液相色谱法同时测定食品中10种合成着色剂(柠檬黄、新红、觅菜红、靛蓝、胭脂红、日落黄、诱惑红、亮蓝、喹琳黄、赤藓红).方法 用GB/T 5009.35-2003(食品中人工合成着色剂的测定方法)中试样处理方法制备样品溶液,聚酰胺吸附法提取色素,以甲酵/乙睛(3+1)+乙酸铵(0.02 mol/L,pH =4.0)为流动相,梯度淋洗分离,多波长检测定量.结果 线性范围分别为柠檬黄、觅菜红、靛蓝、胭脂红、日落黄于0.94-30.00p.g/ml,新红于0.94～30.00μg/ml,诱惑红于1.00～32.10μg/ml,亮蓝于0.31～10.00μg/ml,喹琳黄于1.219.68μg/ml,赤藓红于0.76～24.40μg/ml,线性关系良好,相关系数0.999 0～1.000 0,回收率87.5% - 101.4%,RSD 1.3%～5.7%,检出限分别为0.03～ 0.9 mg/kg.结论 该方法简单、准确、灵敏,适用于食品中10种合成着色剂的定量分析.     

某企业不同工种的放射工作人员发生甲状腺结节风险分析

采用职业健康体检资料和问卷形式,利用单因素和多因素logistic回归模型,分析探讨某企业内不同工种的放射工作人员暴露在低剂量电离辐射环境下发生甲状腺结节的风险。结果表明,放射工作人员中以混合射线组甲状腺结节发生风险最高,随着年龄和放射工龄的增加发生风险会增加;性别不同与甲状腺结节发生风险有关。     

2015~2017年江苏省食品中多环芳烃污染状况的调查分析

目的 调查江苏省辖区内的食物中多环芳烃的污染水平现况。方法 收集2015~2017年江苏省13市区流通和餐饮环节的油炸食品、速食面、食用油类等样品, 采用高效液相色谱荧光检测器测定15种多环芳烃的含量。结果 采集5类食物共277份, 15种多环芳烃的检出率为18.8%, 各类食品中目标化合物检出含量范围: 油炸面类食品0.3~197.7 μg/kg; 速食面0.3~72.0 μg/kg; 食用油0.3~27.4 μg/kg; 果蔬类 0.1~2.56 μg/kg; 谷物0.1~6.92 μg/kg。苯并(a)芘(BaP)均未超标。结论 江苏省内食品中存在多环芳烃的污染状况, 15种多环芳烃的总含量的均值以油炸面类食品和食用油最高, 速食面次之, 谷物与果蔬类处于较低水平。