动物源性食品中抗生素残留、耐药细菌的分布及耐药基因的水平传播

目的：调查动物源性食品中抗生素的残留、耐药细菌的分布及抗生素对耐药基因水平转移的影响。方法：利用盐析辅助液液萃取/高效液相色谱/串联质谱法对市售动物源性食品中18种抗生素的含量进行检测;对样品中的需氧菌进行分离鉴定,利用PCR技术调查耐药基因的分布,通过接合转移试验调查抗生素胁迫对耐药基因水平传播的影响。结果：50份动物源性食品中检出环丙沙星、恩诺沙星、土霉素、金霉素、磺胺嘧啶和磺胺二甲嘧啶。162株分离株中磺胺甲基异恶唑耐药基因sul1的检出率最高。在环丙沙星胁迫下,三株供体菌中耐药基因qnrS的接合转移率均高于对照组。结论：动物源性食品中喹诺酮类、磺胺类和四环素类抗生素均有不同程度的残留。亚抑菌浓度抗生素促进耐药基因的接合转移。     

我国食品用消毒剂风险评估方法的建立及其应用研究

目的 以禽屠宰加工用过氧乙酸消毒剂为模式物,建立食品用消毒剂的安全性评估方法。方法 参考国际组织关于食品用消毒剂的风险评估方法,综合考虑消毒剂对人体的健康影响、消毒效果和耐药性,建立适用于我国的食品用消毒剂风险评估方法。使用建立的评估方法,对用于禽屠宰环节胴体消毒的过氧乙酸消毒剂进行安全性评估。结果 过氧乙酸消毒剂在设定使用情形下,其成分过氧乙酸、乙酸、过氧化氢、羟基乙叉二膦酸以及消毒副产物和反应产物对人体的健康风险无需优先关注。对比现有资料,未发现使用过氧乙酸消毒剂会导致杀菌剂消毒效果下降和/或与细菌出现抗微生物耐药有关。结论 本研究建立了我国食品用消毒剂风险评估方法,可为后续开展食品用消毒剂新品种安全性评估提供方法学基础。     

欧洲食品安全局(EFSA)细菌耐药性评估概述

细菌对抗生素耐药性(药物敏感性)是国际国内的热点问题。该文围绕欧洲食品安全局(EFSA)相关法规对食品和饲料工业用细菌抗生素耐药性监管及评估体系进行了概述,包括最低抑菌浓度(MIC)法表型耐药性及基因水平耐药性评价等,以期为我国细菌耐药性的监管和评估提供借鉴。     

食品中克罗诺杆菌分离菌株生物被膜形成、耐药性及毒力基因检测

研究食品中克罗诺杆菌分离菌株的生物被膜形成、耐药性以及携带毒力基因情况。在成都市周边农贸市场和路边小摊采集食品样品129份,采用DFI 阪崎肠杆菌显色培养基分离克罗诺杆菌;通过16S rRNA序列比对分析鉴定分离菌株;采用试管法和微孔板法分析菌株生物被膜形成能力,同时研究温度对细菌成膜能力影响;采用纸片法检测分离菌株对18种抗生素的耐药性;采用PCR方法检测分离菌株携带cpa、hly、sip 和ompX毒力基因情况。结果发现从129份食品样本中共检出克罗诺杆菌43株,检出率为33.3%。43株克罗诺杆菌食品分离菌株的成膜率为90.7%,并且温度对细菌成膜影响明显。四种毒力基因中,ompX检出率为100%;cpa检出率为13.9%;hly检出率为11.6%;sip基因未检出。耐药表型检测发现43株克罗诺杆菌食品分离菌株对青霉素、克林霉素、万古霉素、苯唑西林和杆菌肽B的耐药率为100%,对利福平的耐药率达97.7%;对红霉素的耐药率为7%;对环丙沙星、庆大霉素、四环素、氯霉素、亚胺培南、磺胺甲恶挫、呋喃妥因、头孢西丁、链霉素、阿米卡星、氧氟沙星等100%敏感。本研究表明克罗诺杆菌食品分离菌株具有较好的形成生物被膜能力,对常见的抗生素耐药率较高,并且分离菌株携带一定的毒力基因,对食品安全造成潜在威胁。     

宁波地区食品中致病菌污染物检测与调查

目的 了解宁波地区食品中携带或污染的致病菌,为控制食源性疾病提供依据.方法 致病菌检测采用直接分离与增菌分离相结合的方法;细菌鉴定采用生化筛检和API等方法;血清分型采用诊断血清凝集法;药敏试验采用K-B法;采用PCR检测耐药基因.结果 从6 812份食品标本中检出致病菌7类12种,共2 331株,检出率为34.22％,以副溶血性弧菌检出率最高,与其他病原菌检出率比较差异有统计学意义(P＜0.005).主要流行株副溶血性弧菌分型发现10个血清群,O∶6群和O∶5群为优势群.检出的致病菌对大多数抗生素敏感,其中3株气单胞菌为带aacc耐药基因的多重耐药菌.结论 宁波地区食品中致病菌构成复杂,食品污染是引起食源性疾病的主要原因,其中副溶血性弧菌是最主要的流行菌株;检出的致病菌对多种抗生素敏感,存在aacc耐药菌应引起关注,控制的关键是采取合理用药,加强对耐药菌株的监测,以减少耐药菌的传播和扩散.     

北京市售生鲜猪肉和牛肉中有害细菌的鉴定及耐药性分析

采用选择性培养基初步筛选,结合16S rRNA同源性分析的方法,对北京市农贸市场及超市中所销售的生鲜猪、牛肉中含有的有害细菌的分布情况进行考察。对分离得到的细菌针对7种常见抗生素进行耐药表型检测。同时,利用特异性PCR扩增法检测了2个常见红霉素耐药基因和7个常见四环素耐药基因在分离细菌中的分布情况。结果表明:市场中购买的生鲜肉中分离得到的细菌耐药情况较之超市中的更为严重;猪肉和牛肉中分离的细菌耐药情况均十分严重;分离得到的不同细菌中包含某些条件致病菌的Escherichia/Shigella以及Aeromonas属细菌耐药情况更加严重。同时,研究还发现在北京市售鲜肉中分离得到的细菌中,绝大多数细菌对不止1种抗生素表现出非敏感(耐药及中介),且一些菌株携带多种不同的耐药基因。因此,市售生鲜肉中分离得到的细菌耐药情况较为严重以及普遍,应得到监管部门以及普通消费者的足够重视。     

我国食品中大肠埃希菌O157耐药及PFGE分子分型特征分析

了解我国食品中分离的110株大肠埃希菌O157的耐药及脉冲场凝胶电泳(PFGE)分子分型特征,完善我国食品中大肠埃希菌O157菌株特征的基础信息,为该菌的风险评估提供依据。方法 使用琼脂稀释法对确认的110株大肠埃希菌O157进行药敏试验,完成耐药特征的分析。参照美国疾病预防控制中心PulseNet试验方法,对110株大肠埃希菌O157,运用XbaⅠ酶进行酶切并完成PFGE分析,利用BioNumerics软件对分离株的指纹图谱进行聚类分析。结果 ①110株菌中,43株菌至少对一种抗生素有抗性。耐药率最多的前三种抗生素依次是四环素(30.0%,33/110),磺胺甲恶唑(29.1%,32/110),萘啶酸(26.4%,29/110);②一共有24个耐药谱,耐两种以上抗生素的菌株有34株,耐3种以上抗生素的多重耐药菌株有32株。最常见的三种耐药谱依次是SMX(6),AMP-NAL-SMX-SXT-TET(6),AMP-CHL-NAL-SMX-SXT-TET(4)/AMP-SMX-SXT-TET(4)/TET(4);③大肠埃希菌O157非H7 (O157∶hund)对所测试的抗生素的耐药率明显高于大肠埃希菌O157∶H7(χ²=72.010 P<0.05)。其中37株携带了志贺毒素基因的大肠埃希菌O157∶H7仅对磺胺甲恶唑(2.7%,1/37)、萘碇酸(2.7%,1/37)有耐药,没有多重耐药菌株;④通过不同种类食品中大肠埃希菌O157菌株耐药率比较发现,从生猪肉、生禽肉中分离的菌株耐药率相对高于其他食品种类;⑤PFGE分子分型研究显示菌株具有基因多态性,且可以很好将大肠埃希菌O157非H7和大肠埃希菌O157∶H7菌株区分开。结论 我国食品中分离的大肠埃希菌O157耐药现象严重。我们应加强养殖环节和零售环节食源性致病菌,特别是大肠埃希菌O157(包括产志贺毒素大肠埃希菌O157)菌株药敏特征的监测,探明食品与养殖环节菌株耐药的传播关系,并为国家制定科学的养殖业抗生素用药提供依据。     

市售即食食品中非致病菌的耐药性及耐药基因转移的研究

目的 了解西安市即食食品中的非致病菌的耐药性分布、耐药程度及耐药基因的转移情况,分析潜在的食品安全问题.方法 对西安市的几家大型超市零售的熟肉、果盘、凉拌菜3大类即食食品样品进行食源性非致病菌的红霉素和氨苄青霉素耐药性分析、耐药基因转移、菌株16 S rRNA序列测序鉴定等.结果 42.5％的分离株具有不同程度的红霉素耐药性,47.5％的分离株具有不同程度的氨苄青霉素耐药性,21.2％的分离株同时具有2种抗生素耐药性;11.3％的红霉素耐药株耐药性高达160 mg/L,6.3％的氨苄青霉素耐药株耐药性高达500 mg/L.随机挑选的部分耐药株在无抗生素培养基中连续传代1000代以后,60％的氨苄青霉素耐药株和45％的红霉素耐药株的耐药性消失.部分耐药株的耐药基因可水平转移至非耐药株中.这些耐药株多为肠球菌、葡萄球菌、芽孢杆菌、假单胞菌等.结论 即食食品中的非致病菌有潜在的风险,耐药基因在细菌间的转移可能对人体敏感肠道菌群和致病菌有一定影响.     

2012~2014年我国婴幼儿食品中克罗诺氏菌 耐药特征分析

目的阐述2012~2014年中国27个省(直辖市,自治区)分离自市售谷类辅助食品、婴幼儿配方食品、罐装辅助食品和其他乳制品等4类食品的417株克罗诺氏菌的药敏特征。方法参考美国临床实验室标准化委员会(Clinical and Laboratory Standards Institute,CLSI)推荐的微量肉汤稀释法,选择氨苄西林、阿莫西林、头孢噻肟、头孢他啶、萘啶酸、氨苄西林/舒巴坦、四环素、庆大霉素、环丙沙星、氯霉素、复方新诺明在内的9大类11种抗生素进行克罗诺氏菌的耐药特征分析。结果 417株克罗诺氏菌中有8株耐药,平均耐药率1.92%,其中7株耐药克罗诺氏菌来源于谷类辅助食品。耐药株中耐阿莫西林3株、氨苄西林2株、氯霉素2株、头孢噻肟1株、萘啶酸1株、复方新诺明1株、四环素1株。有3株菌耐受2种抗生素。28株菌抗生素中介,其中阿莫西林中介16株,氯霉素中介15株,头孢他啶中介1株。结论我国2012~2014年市售婴幼儿食品来源的克罗诺氏菌总体对抗生素敏感,耐药菌株主要来源于谷类辅助食品,阿莫西林和氯霉素显示出一定的耐药趋势,应持续监测以阐述主要抗生素的耐药变化规律。     

质粒介导的氨苄西林耐药肠炎沙门氏菌生长特性及抗性研究

肠炎沙门氏菌是一种重要食源性致病菌，其耐药性成为全球关注的问题。耐药质粒的广泛传播提高了肠炎沙门氏菌的耐药性，耐药质粒的获得可能会改变细菌的生长特性及对环境压力的抗性，这给耐药食源性致病菌的控制及风险评估带来了新的挑战。为探究质粒介导的氨苄西林耐药性对肠炎沙门氏菌生长以及抗性变化的影响，该研究将含有氨苄西林抗性基因的pKD46质粒导入到抗生素敏感的肠炎沙门氏菌中，获得氨苄西林耐药菌株。分别对转化后的耐药沙门氏菌的生长特性、酸与热抗性进行检测。结果发现耐药质粒转化后的肠炎沙门氏菌菌株对其他种类抗生素的抗性基本不变；生长的最大比生长速率(μ_max)不变，生长延滞期(λ)延长；在57.5与60℃条件下的热抗性显著降低；对pH 3.0的酸抗性未发生显著改变。研究结果发现质粒介导的氨苄西林耐药性可降低肠炎沙门氏菌的生长及热抗性，该结果可为耐药食源性致病菌的控制及风险评估提供参考。     

乳酸菌合成共轭亚油酸及其应用研究进展

共轭亚油酸(conjugated linoleic acid,CLA)是一种具有多种生理活性的功能性脂肪酸,在食品、保健品中具有广阔的应用前景。然而,天然来源的CLA含量很低,不能满足人类需求。乳酸菌可以合成CLA,且广泛用于食品加工领域,利用乳酸菌开发富含CLA的功能食品是当今的研究热点。为推动CLA功能食品的研究开发,该文对合成共轭亚油酸乳酸菌的研究进展、合成共轭亚油酸乳酸菌的益生性研究以及将产CLA乳酸菌应用到食品和饲料中的研究现状进行综述,并对利用乳酸菌合成CLA进而应用于功能食品进行展望。     

Ready-to-eat shrimp as an international vehicle of antibiotic-resistant bacteria

The occurrence of antibiotic-resistant bacteria in foods of animal origin is a potential health threat because resistance can be transferred among bacteria, and antibiotic-resistant pathogens may not respond to antibiotic treatments. Thirteen brands of ready-to-eat shrimp representing four countries of origin were obtained from local grocery stores. Total heterotrophic plate counts were determined, and antibiotic-resistant bacteria were isolated. Total heterotrophic colony counts ranged from 3.3 to 5.6 log CFU/g, which was within approved quality limits. A total of 1,564 isolates representing 162 bacterial species were recovered during screening of resistance to 10 antibiotics: ampicillin, ceftriaxone, chloramphenicol, clindamycin, erythromycin, nalidixic acid, streptomycin, tetracycline, trimethoprim, and vancomycin. Six hundred fifty-seven (42%) of the isolates and 131 (81%) of the species had acquired resistance to antibiotics. Numerous resistant human pathogens were isolated, including Escherichia coli, Enterococcus spp., Salmonella, Shigella flexneri, Staphylococcus spp., and Vibrio spp. Nonresistant Yersinia spp. also were isolated. Ready-to-eat shrimp is sold with instructions to thaw the product before serving, which may result in consumer exposure to antibiotic-resistant bacteria. Widespread trade of this product provides an avenue for international dissemination of antibiotic-resistant pathogens.     

Emerging microbiological food safety issues related to meat

Avian influenza viruses and antibiotic-resistant pathogens have become topics of current public health interest. This paper will focus on the significance of these pathogens to the meat industry as well as other emerging microbiological food safety topics likely to impact the meat industry. These include surveillance of foodborne pathogens, microbial source tracking, risk assessment, and human populations at increased risk of infection by foodborne microbes. These emerging issues will likely lead to even greater challenges to producing microbiologically safe meat products than the industry has ever experienced. However, accompanying such challenges will be innovative solutions that provide even greater public health protection to meat-containing foods.     

Fermentation and pathogen control: a risk assessment approach

Food fermentation has a long tradition of improving the safety, shelf life and acceptability of foods. Although fermented foods generally enjoy a well-founded reputation for safety, some notable outbreaks of foodborne illness associated with fermented foods have occurred. Microbiological risk assessment (MRA), as it has emerged in recent years, provides the scientific basis for the control and management of risk. Aspects of fermented food processes are discussed under the various stages of risk assessment and data are presented that would inform more detailed risk assessments.     

Public health consequences of macrolide use in food animals: a deterministic risk assessment

The potential impact on human health from antibiotic-resistant bacteria selected by use of antibiotics in food animals has resulted in many reports and recommended actions. The U.S. Food and Drug Administration Center for Veterinary Medicine has issued Guidance Document 152, which advises veterinary drug sponsors of one potential process for conducting a qualitative risk assessment of drug use in food animals. Using this guideline, we developed a deterministic model to assess the risk from two macrolide antibiotics, tylosin and tilmicosin. The scope of modeling included all label claim uses of both macrolides in poultry, swine, and beef cattle. The Guidance Document was followed to define the hazard, which is illness (i) caused by foodborne bacteria with a resistance determinant, (ii) attributed to a specified animal-derived meat commodity, and (iii) treated with a human use drug of the same class. Risk was defined as the probability of this hazard combined with the consequence of treatment failure due to resistant Campylobacter spp. or Enterococcus faecium. A binomial event model was applied to estimate the annual risk for the U.S. general population. Parameters were derived from industry drug use surveys, scientific literature, medical guidelines, and government documents. This unique farm-to-patient risk assessment demonstrated that use of tylosin and tilmicosin in food animals presents a very low risk of human treatment failure, with an approximate annual probability of less than 1 in 10 million Campylobacter-derived and approximately 1 in 3 billion E. faecium-derived risk.     

食品中大肠杆菌O157:H7的预测模型及风险评估

大肠杆菌O157:H7是严重危害人类健康的肠道致病菌,感染剂量极低,低达10个菌体。由该菌引起的食物中毒十分凶险,引起世界各国的重视。该菌引起的感染主要通过食品传播,因此加强食品卫生管理,防止食源性感染和流行尤为迫切。本文就大肠杆菌O157:H7在食品中的预测模型以及风险评估进行了概述。     

Risk assessment of aflatoxins in food in Africa

Aflatoxins are secondary metabolites of the fungi Aspergillus flavus and A. parasiticus, occur widely on many staple foods and cause a broad range of detrimental health effects in animals and humans. As a consequence, maximum tolerated levels (MTLs) have been legislated in many countries. However, in developing countries where food safety compliance can be low and significant levels of the food supply are locally consumed by the producers or purchased at local markets, more comprehensive strategies are required. In this regard, risk analysis with its components of risk assessment, risk management and risk communication, is an important tool in dealing with food safety issues. Risk assessment for aflatoxin B(1) in Africa has been performed using the carcinogenic potency, established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and applying it to typical food products and consumption across the continent, to illustrate the significant health implications caused by the intake of high levels of contaminated foods. Highlighted in this assessment is the fact that even low levels of contamination, which might of themselves fall within legislated limits, can have serious health implications due to high levels of consumption, i.e. meeting a MTL does not of itself guarantee food safety. Recent developments have highlighted the growth retardation and immune suppression caused by aflatoxin exposure in human populations in west Africa. Using the limited data available on both these health effects, a first step has been taken to incorporate them into a risk assessment paradigm quantifying the risk of immunosuppression, malnutrition and stunting in children exposed to aflatoxins and highlighting again how excessive consumption of foods meeting MTLs can carry significant health risks.     

Research on factors allowing a risk assessment of spore-forming pathogenic bacteria in cooked chilled foods containing vegetables: a FAIR collaborative project

Vegetables are frequent ingredients of cooked chilled foods and are frequently contaminated with spore-forming bacteria (SFB). Therefore, risk assessment studies have been carried out, including the following: hazard identification and characterisation — from an extensive literature review and expertise of the participants, B. cereus and C. botulinum were identified as the main hazards; exposure assessment — consisting of determination of the prevalence of hazardous SFB in cooked chilled foods containing vegetables and in unprocessed vegetables, and identification of SFB representative of the bacterial community in cooked chilled foods containing vegetables, determination of heat-resistance parameters and factors affecting heat resistance of SFB, determination of the growth kinetics of SFB in vegetable substrate and of the influence of controlling factors, validation of previous work in complex food systems and by challenge testing and information about process and storage conditions of cooked chilled foods containing vegetables. The paper illustrates some original results obtained in the course of the project. The results and information collected from scientific literature or from the expertise of the participants are integrated into the microbial risk assessment, using both a Bayesian belief network approach and a process risk model approach, previously applied to other foodborne hazards.     

Occurrence of antibiotic-resistant enterobacteria in agricultural foodstuffs

Antibiotic-resistant bacteria or their corresponding resistance determinants are known to spread from animals to humans via the food chain. We screened 20 vegetable foods for antibiotic-resistant coliform bacteria and enterococci. Isolates were directly selected on antibiotic-containing selective agar (color detection). Thirteen "common vegetables" (tomato, mushrooms, salad) possessed 10(4)-10(7) cfu/g vegetable of coliform bacteria including only few antibiotic-resistant variants (0-10(5) cfu/g). All seven sprout samples showed a some orders of magnitude higher contamination with coliform bacteria (10(7)-10(9) cfu/g) including a remarkable amount of resistant isolates (up to 10(7) cfu/g). Multiple resistances (up to 9) in single isolates were more common in sprout isolates. Resistant bacteria did not originate from sprout seeds. The most common genera among 92 isolates were: 25 Enterobacter spp. (19 E. cloacae), 22 Citrobacter spp. (8 C. freundii), and 21 Klebsiella spp. (9 K. pneumoniae). Most common resistance phenotypes were: tetracycline (43%), streptomycin (37%), kanamycin (26%), chloramphenicol (29%), co-trimoxazol (9%), and gentamicin (4%). The four gentamicin-resistant isolates were investigated in molecular details. Only three (chloramphenicol) resistant, typical plant-associated enterococci were isolated from overnight enrichment cultures. In conclusion, a contribution of sprouts contaminated with multiresistant, Gram-negative enterobacteria to a common gene pool among human commensal and pathogenic bacteria cannot be excluded.