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.     

Rapid determination of polybrominated diphenyl ethers (PBDEs) in fish using selective pressurized liquid extraction (SPLE) combined with automated online gel permeation chromatography-gas chromatography mass spectrometry (GPC-GC/MS)

A rapid method for the determination of seven predominant polybrominated diphenyl ethers (PBDEs) in fish was developed. The analysis could be completed in 1 h. The PBDEs in the sample were extracted with fat by selective pressurized liquid extraction (SPLE) using acid alumina as a fat retainer. After concentration, the extract was directly injected into online gel permeation chromatography with gas chromatography-mass spectrometry (GPC-GC/MS) in negative chemical ionization (NCI) mode. Method detection limits of seven PBDEs were between 0.002 and 0.005 ng g^?1 fat. Quantitative recoveries ranging from 81.9% to 110.3% were obtained by analysis of spiked fish. The relative standard deviations were less than 15% (n = 6). The method was applied to a certified reference material of fish; all results were in the reference ranges. It was shown to be a rapid and reliable alternative in the routine analysis for PBDEs.     

我国首例由丁酸梭菌引起婴儿E型肉毒中毒实验室诊断研究

目的对一起疑似婴儿肉毒中毒进行实验室诊断研究。方法对1例疑似婴儿肉毒中毒病例的粪便、食用过的食品和生活环境涂抹共计30份标本/样品进行梭菌分离鉴定及肉毒毒素检测,对分离菌株进行产毒试验。结果将患儿粪便标本培养物上清液腹腔注射小鼠后可致小鼠出现典型肉毒毒素中毒表现(竖毛、呼吸困难并出现典型的蜂腰、四肢麻痹),继而死亡,且培养物上清液经胰酶处理后毒性增强,表现为小鼠出现中毒及死亡时间较未处理组明显缩短。但培养物上清液经100℃加热处理后再次染毒动物,小鼠未出现中毒和死亡。混合型肉毒毒素诊断血清及单价抗E型肉毒毒素诊断血清可对小鼠起到保护作用。从患儿的粪便标本中分离到G~+芽胞杆菌,该菌在哥伦比亚血平板上呈不规则半透明扁平菌落,边缘根状生长,并携带E型肉毒毒素产毒基因,16S rRNA将其鉴定为丁酸梭菌,产毒试验结果显示该菌株可产E型肉毒毒素。结论该起婴儿中毒事件是由感染产E型肉毒毒素的丁酸梭菌引起。     

Adaptive recommendation for photo pose via deep learning

Multimedia Tools and Applications - With the development of image acquisition devices and the popularity of smart phones, more and more people would like to upload their photos to diverse social...     

Kinetic analysis of the thermal decomposition of Polygonum lapathifolium

The optimal reaction model for analysis of thermal decomposition of various types of biomasses is currently under debate. Four established models for the kinetic analysis of Polygonum lapathifolium were employed in this study: double extrapolation method, Flynn–Wall–Ozawa method (FWO), distributed activation energy model (DAEM), and global kinetic model. The values of activation energy and frequency factor calculated by global kinetic model are much lower than that of the other three methods. Moreover, it has been demonstrated that the activation energy analyzed by FWO method and DAEM is widely distributed and is not directly related to the heating rates, which are more objective than double extrapolation method and global kinetic model.     

Occurrence of four mycotoxins in cereal and oil products in Yangtze Delta region of China and their food safety risks

A total of 76 cereal and oil products collected from Yangtze Delta region of China were analyzed for occurrences of aflatoxins (AFs), aflatoxin B₁ (AFB₁), ochratoxin A (OTA), deoxynivalenol (DON) and zearalenone (ZEN). The mycotoxins were determined by the standard detection procedures using immunoaffinity column clean-up coupled with fluorometer (or HPLC-UV). ZEN was the most prevalent toxin, with the incidence of 27.6% (range = 10.0–440.0 μg kg⁻¹), and 9.2% of the evaluated samples were contaminated with a concentration higher than that of the legislation limit of China (60 μg kg⁻¹). AFs and AFB₁ were detected in 14.5% of the samples analyzed, the concentrations ranging 1.1–35.0 μg kg⁻¹ for AFs, and 1.0–32.2 μg kg⁻¹ for AFB₁; 4.0% of the samples had the concentrations of AFs and AFB₁ higher than that of the corresponding legislation limits of China (5.0, 10.0 and 20.0 μg kg⁻¹ for different products). OTA was detected in 14.5% of the cereal and oil products collected; the concentrations ranged 0.51–16.2 μg kg⁻¹. Only 2 samples showed OTA levels higher than that of the legislation limit of China (5.0 μg kg⁻¹). DON was detected in 7.9% of the samples; the concentrations ranged 100–700 μg kg⁻¹, and none of the samples showed DON concentration higher than that of the legislation limit of China (1.0 mg kg⁻¹). A total of 15.8% cereal and oil products were contaminated with at least two mycotoxins (multiple contaminations with different combinations including AFs-ZEN, AFs-OTA-ZEN, OTA-ZEN, ZEN-DON, OTA-ZEN-DON). The dietary exposure assessment results indicated that AFs (AFB₁), OTA, DON and ZEN from cereal-based products represented a series health risk to both adults and children in Yangtze Delta region of China. This is the first report of safety evaluation associated with major mycotoxins for the area.     

2018—2020年天津市津南区食源性致病菌分布及药敏分析

目的 对2018—2020年天津市津南区食源性致病菌污染进行监测及耐药分析,了解天津市津南区食源性疾病流行病学特征和耐药情况,为预防和控制食源性疾病提供依据。方法 对2018—2020年津南区哨点医院607例食源性疾病粪便标本进行沙门菌、致泻大肠埃希菌、副溶血性弧菌和志贺菌4种致病菌检测,并对阳性菌株做药敏分析。结果 607例粪便标本中共检出阳性菌株124株,阳性检出率20.43%(124/607)。其中沙门菌74株,副溶血性弧菌31株,致泻大肠埃希菌19株,未检出志贺菌。患者中,男∶女为4∶3(347/260);沙门菌中肠炎沙门菌检出率最高,达62.16%(46/74),致泻大肠埃希菌中肠致病性大肠埃希菌(EPEC)检出率最高;药物敏感试验中,沙门菌和致泻大肠埃希菌对氨苄西林(AMP)耐药显著,高达72.04%(67/93),且普遍存在多重耐药情况,副溶血性弧菌对头孢唑啉(CFZ)的耐药最严重[77.42%(24/31)]。结论 天津市津南区2018—2020年引起腹泻的食源性疾病致病菌以肠炎沙门菌、EPEC为主。分离菌株普遍对AMP耐药,且存在多重耐药情况,提示相关部门应加强对食品加工业的监管,同时加强致病菌耐药的监测力度,为津南区食品安全和临床治疗提供依据。     

The effects of washing and cooking on chlorpyrifos and its toxic metabolites in vegetables

The effect of household processing on removal of chlorpyrifos residue from vegetables, and the formation of metabolite during processing were studied. Many factors: washing solutions, pH value, cooking mode, processing time were investigated. Analysis of chlorpyrifos and its metabolites was carried out by gas chromatography coupled to triple quadrupole mass spectrometry. Hydrolysis of chlorpyrifos affected the removal of residue from leafy vegetable during washing. Cooking on removal of chlorpyrifos residue was more effective than washing. Chlorpyrifos degraded into 3,5,6-trichloro-2-pyridinol during cooking, while chlorpyrifos did not degrade into chlorpyrifos oxon in all experiments.