发酵肉中凝固酶阴性葡萄球菌快速鉴定

介绍一种凝固酶阴性葡萄球菌(CNS)快速鉴定方法:“两步一补法”。并用此方法鉴定传统发酵肉中CNS的分布情况。CNS菌株先经二步鉴定:第一步4h,包括:蕈糖、尿素酶、碱性磷酸酶;第二步24h,包括:鸟氨酸脱羧酶、新生霉素敏感性、磷霉素敏感性、厌氧生长。极少数不能鉴定的CNS菌株,用补充试验完成结果。本方法能鉴定出发酵肉中CNS的22个种及2个亚种,两步法能鉴定出发酵牛肉中77%以上常见CNS菌种,仅23%的菌株需用补充实验证实。     

肉源凝固酶阴性葡萄球菌对多环芳烃的消减作用

多环芳烃（polycyclic aromatic hydrocarbons,PAHs）是一类食品中广泛存在的危害物,降低其含量有利于提升产品安全性。在模拟体系中考察不同肉源凝固酶阴性葡萄球菌对PAHs 的消减作用,筛选出消减PAHs 能力最强的菌株,并探讨其作用机理。研究结果表明：在受试菌株中,马胃葡萄球菌（Staphylococcus equorum）E1 对模拟体系中PAHs 的消减效果最强（P<0.05）。在S.equorum 不同细胞组分中,全细胞提取液（whole cell extracts,WCE）和细胞碎片悬液均对PAHs 有显著的降低作用（P<0.05）。进一步酶处理发现,WCE 中关键消减物质是蛋白类物质;同时,在WCE中检测到了PAHs 降解酶活性,这表明S.equorum 消减PAHs 存在生物降解途径。另一方面,热灭活处理使S.equorum对PAHs 消减能力显著提升（P<0.05）;通过傅里叶变换红外光谱分析,发现S.equorum 的WCE 存在与物理吸附PAHs相关的官能团,说明S.equorum 消减PAHs 存在物理吸附途径。因此,S.equorum 可通过生物降解和物理吸附两种作用途径消减PAHs。研究为生物法消减食品中的多环芳烃提供了新途径。     

乳源凝固酶阴性金黄色葡萄球菌挥发性代谢特征分析

为探究乳源金黄色葡萄球菌的挥发性代谢特征,从牛乳中分离得到5株凝固酶阴性金黄色葡萄球菌(31B、0250H、777H、S12-1和S2-2),采用顶空固相微萃取/气相色谱-质谱联用技术,分别对接种这5株菌的胰蛋白胨大豆肉汤(tryptic soy broth,TSB)和牛乳的挥发性代谢产物进行动态测定。结果表明,TSB中5株菌总计检出33个挥发性代谢产物,1-丁醇、乙酸、3-甲基-丁酸和2-丁酮是5株菌共同检出的典型挥发性代谢产物。牛乳中5株菌总计检出28个挥发性代谢产物,2-呋喃甲醇、辛酸和3-甲基-丁酸是5株菌共同检出的典型挥发性代谢产物。无论是在TSB还是牛乳中,3-甲基-丁酸始终是凝固酶阴性金黄色葡萄球菌稳定的挥发性代谢产物。不同菌株产生3-甲基-丁酸的强度不相同,同一菌株在TSB和牛乳两种不同基质中3-甲基-丁酸的产生强度也不相同。     

3M测试片葡萄球菌血浆凝固酶试验方法研究

为解决玻片法葡萄球菌凝固酶试验假阳性的问题,提高其检测的敏感性和特异性。以试管法为金标准,用玻片法进行不同血浆稀释度试验的方法研究。检测170株葡萄球菌凝固酶,其中检出金黄色葡萄球菌38株,溶血葡萄球菌80株,表皮葡萄球菌28株,其他葡萄球菌24株。对于不同的血浆稀释度,检出的敏感性和特异性各有不同。玻片法血浆浓度是否合适,直接影响血浆凝固酶试验的效率。研究证明:1:16～1:32为最佳稀释范围。该文选择1:16为玻片法的血浆稀释度。     

LAMP法检测食品中凝固酶阳性葡萄球菌

建立凝固酶阳性葡萄球菌环介导等温扩增方法(LAMP),运用在食品样品检测中,与实时荧光PCR方法及国家标准检测方法进行比较。以毒力因子——凝固酶的编码基因coa为目的基因设计引物,建立环介导等温扩增方法,对9株凝固酶阳性葡萄球菌和31株对照菌(均为凝固酶阴性)进行测试,并对5种共1 341份食品进行检测。建立的方法具有很好的特异性,检测灵敏度可达到1.8 CFU/100 g～2.5 CFU/100 g。     

食品中一株凝固酶异常的金黄色葡萄球菌的分离鉴定

目的 对餐饮环节采集的一份鸡排进行金黄色葡萄球菌检验时,发现一株血浆凝固酶试验异常的金黄色葡萄球菌,并对其分离、鉴定、分析和总结,避免因不典型菌株的漏检而带来的食品安全风险。方法 采用国标法检测金黄色葡萄球菌,血浆凝固酶试验时间延长至24h,同时用生化鉴定法和BAX System Q7快速检测法进行互相验证。结果 国标法凝固酶试验6h不凝固,12h出现部分凝固,24h完全凝固,生化鉴定法和BAX System Q7快速检测法结果都是检出金黄色葡萄球菌。结论 在食品中金黄色葡萄球菌检验过程中,选择性平板上菌落典型,而凝固酶试验异常的情况,应延长试验时间并用其他方法加以验证。     

广州市白云口岸航空食品中金黄色葡萄球菌凝固酶基因分型及肠毒素基因研究

目的对2013—2015年从广州市白云口岸航空食品中分离的金黄色葡萄球菌进行基因分型研究,为食源性金黄色葡萄球菌分子溯源提供基础数据。方法以血浆凝固酶和肠毒素为目标基因,采用聚合酶链式反应(PCR)方法对9株金黄色葡萄球菌进行基因分型,其中6株为航空食品分离株,1株为配餐车间大门手拭分离株,2株为标准菌株。肠毒素基因检测包括5种传统肠毒素基因(sea、seb、sec、sed、see)和6种新型肠毒素基因(ser、seg、seh、sei、sej、sep)。结果 6株航空食品分离株的血浆凝固酶基因扩增分型结果为2个PCR型,酶切后得3种亚型;肠毒素基因检测结果显示有2株航空食品分离株含有肠毒素基因,检出率为33.3%(2/6),检出的基因为2种传统肠毒素基因(sec、sed)和4种新型肠毒素基因(ser、seg、sei、sej),均同时携带2种以上肠毒素基因。结论血浆凝固酶基因扩增分型结果显示,不同时间、不同采集地点存在相同的基因型,提示金黄色葡萄球菌存在交叉污染的可能性;航空食品分离株共检出6种肠毒素基因,提示金黄色葡萄球菌基因型多样性,应加强其他新型肠毒素基因检测。     

金黄色葡萄球菌血浆凝固酶试验──四种血浆的对比性试验

金黄色葡萄球菌血浆凝固酶试验──四种血浆的对比性试验徐素荣盐城商检局２２４００２食品中金黄色葡萄球菌血浆凝固酶试验是金葡萄菌的最后判断标准。为了避免或减少血浆凝固酶试验假阴性或假阳性的发生,使检测结果更加准确,采用鲜兔血浆、冻干兔血浆、人鲜血浆及人废...     

豆乳凝固酶凝固豆乳的工艺条件优化

优选获得ＳＣＥ４豆乳凝固酶，采用响应面分析法（ＲＳＡ）对其制作豆腐坯的凝固条件进行优化，得到最佳实验点为：凝困时问１２．５ｍｉｎ。Ｃａ２＋４．２ｍｍｏｌ／１，ｐＨ６．０，蛋白质凝固率达到８９．６５％。     

试论食用香精香料安全性

食用香精香料作为食品工业一种重要原料,与食品安全息息相关。该文论述食用香精香料功能、香精香料安全性问题及其影响因素,并分析展望如何严控食用香精香料安全性及今后发展趋势。     

Species Diversity and Pheno‐ and Genotypic Antibiotic Resistance Patterns of Staphylococci Isolated from Retail Ground Meats

The presence and species diversity of staphylococci in 250 ground beef and lamb meat samples obtained from Diyarbakir, Turkey were investigated. The presence of the 16S rRNA gene, mecA, nuc, pvl, and femA was analyzed by multiplex PCR. Pheno‐ and genotypic antibiotic resistance profiles of 208 staphylococci isolates were established. Of the ground beef and ground lamb samples, 86.4% and 62.4% were positive for staphylococci, respectively. Staphylococcus aureus, S. saprophyticus, S. hominis, S. lentus, S. pasteuri, S. warneri, S. intermedius, and S. vitulinus made up 40.8%, 28.8%, 11%, 3.8%, 3.8%, 2.4%, 2.4%, and 2.4% of isolates, respectively. Of the 85 S. aureus isolates, 40%, 47%, and 5.8% carried femA, mecA, and pvl, respectively, whereas the corresponding rates for the 118 coagulase‐negative staphylococci (CoNS) were 0%, 10.1%, and 0%, respectively. We determined from the 208 isolates, the highest antibiotic resistances were to tetracycline and oxytetracycline (85.5%), followed by penicillin (51.4%), novobiocin (45.6%), ampicillin (39.9%), and doxycycline (31.7%), using the Clinical and Laboratory Standards Inst. (CLSI) method. All isolates were sensitive to gentamycin, ofloxacin, and tobramycin, but 2.3% of the S. aureus isolates had resistance to vancomycin. The staphylococci isolates carried tet(K), blaZ, tet(L), tet(W), cat, tet(S), tet(M), ermB, ermA, and ermC antibiotic resistance genes at rates of 59%, 51.7%, 36.9%, 31.8%, 27.2%, 27.2%, 24.4%, 18.1%, 7.9%, and 3.9%, respectively.     

Prevalence,Antimicrobial Resistance,and Virulence Characteristics of mecA‐Encoding Coagulase‐Negative Staphylococci Isolated from Soft Cheese in Brazil

Coagulase‐negative staphylococci (CoNS), which are generally neglected as foodborne bacteria, are emerging as significant opportunistic pathogens that may be highly resistant to available antimicrobial drugs. In this study, antimicrobial susceptibility patterns, mecA gene occurrence, and virulence‐associated characteristics were evaluated in CoNS isolated from soft cheese in Brazil. A total of 227 bacterial isolates were recovered from 35 cheese samples belonging to 5 batches with 7 different trademarks. The CoNS counts ranged from 10⁶ to 10⁷ CFU/g. High antimicrobial resistance percentages were observed for oxacillin (76.2%), penicillin (78.5%), erythromycin (67.8%), gentamicin (47.2%), clindamycin (35.7%), rifampicin (26.8%), azithromycin (14.7%), tetracycline (14.7%), levofloxacin (14.2%), and sulfamethoxazole‐trimethoprim (11.9%). A low antimicrobial resistance percentage was observed for chloramphenicol (2.3%), and all of the tested bacteria were susceptible to vancomycin and linezolid. In total, a multiple antibiotic resistance (MAR) index of >0.2 was observed for 80.6% of the isolated CoNS. However, the MAR index ranged from 50% to 92.6% when only bacterial cheese isolates belonging to the same trademark were considered. Regarding to the prevalence of CoNS carrying mecA gene, 81.5% of the isolated strains were mecA⁺, and 76.2% of these were phenotypically resistant to oxacillin. Three isolates carried the enterotoxin A gene (sea), 29.5% produced biofilm in a laboratory test, and α‐ or ß‐hemolysis were observed for 3% and 5.2%, respectively. This study highlights the extent of the antimicrobial resistance phenomenon in neglected foodborne microorganisms and the potential public health risks that are related to the consumption of CoNS‐contaminated soft cheese.     

Behavior and enterotoxin production by coagulase negative Staphylococcus in cooked ham, reconstituted skimmed milk, and confectionery cream

Abstract: In this study, the behavior and enterotoxin production by 10 different coagulase negative Staphylococcus (CNS) strains inoculated in cooked ham, reconstituted skimmed milk, and confectionery cream in the presence or absence of background microbiota have been investigated. After inoculation (10³ CFU/g), foods were incubated at 25, 30, and 37 °C and aerobic mesophilic and CNS counts were carried out at 12, 24, 48, and 72 h. Staphylococcal enterotoxins (SE) detection was performed by SET-RPLA (Oxoid, Basingstoke, U.K.) and mini-Vidas® (bioMérieux, La Balme les Grottes, France). CNS counts increased during incubation and approached 10⁶ to 10⁷ CFU/g after 12 h at 37 °C in the 3 foods studied. At 25 °C, counts reached 10⁶ to 10⁷ CFU/g only after 24 to 48 h. The interference of background microbiota on CNS behavior was only observed when they grew in sliced cooked ham, which presented a high initial total count (10⁵ CFU/g). Significantly higher counts of CNS isolated from raw cow's milk in comparison with food handlers isolates were found in reconstituted milk and confectionery cream. Although CNS strains were able to produce SEA, SEB, and SED in culture media, in foods, in the presence or absence of background microbiota S. chromogenes LE0598 was the only strain able to produce SEs. Despite the scarcity of reports on CNS involvement with foodborne disease outbreaks, the results found here support the CNS growth and SE production in foods even in the presence of background microbiota and may affect food safety.     

传统固态发酵淡水鱼品质及安全性研究进展

传统固态发酵鱼是以鲜鱼为原料,经宰杀、盐腌、晒干后,配以米粉、酒糟等辅料,经密封发酵制成。因其营养丰富、发酵风味浓郁,深受消费者喜爱,在我国、日本及东南亚等地具有很大的需求市场。在我国大多以淡水鱼制作,凭经验进行工艺控制,产品品质不稳定,并存在一定的安全隐患,因此要发展传统固态发酵鱼工业化生产,就需要对其加强应用基础研究。本文概述了传统固态发酵鱼制品理化及风味品质特征,以及从中分离鉴定的优势微生物。同时从产品安全性为出发点,除介绍了腐败菌及致病菌对产品安全性的影响外,还着重对有毒物质生物胺及强致癌物N-亚硝基化合物在产品中的危害、形成机制、检测方法以及预防措施进行了综述,最后展望将改善和稳定传统固态发酵鱼品质以及提高产品安全性作为今后研究的主要内容。     

离子迁移谱技术在食品检测中的应用研究进展

离子迁移谱(ion mobility spectrometry,IMS)是一种利用样品分子电离后离子迁移率的差异进行分离检测的仪器.它具有灵敏度高、选择性好、分析灵活、携带方便、实时监测能力强等优点.因此,广泛应用危险品检测、化工分析、食品检测、医学诊断、生物制药研究及环境监测等领域.该文简要介绍离子迁移谱技术的工作原...     

如皋火腿用霉菌性表面涂膜发酵剂的应用研究

从80条不同发酵期如皋火腿表面自然生长的菌群中,分离到152株霉菌菌株,分属曲霉、青霉和毛霉,剔除5株产毒菌株后,以蛋白酶、脂肪酶活性作为筛选指标,经初筛、复筛,得到1株产蛋白酶、脂肪酶活性强,对革兰氏阳性球菌、杆菌有抑制作用,不产生真菌毒素的菌株P111,经形态结构和显微观察鉴定为产黄青霉,以该菌株涂布接种于刚上架的腌腿表面,生成的火腿香气浓郁,口感鲜嫩。