食品中大肠杆菌检测方法研究进展

大肠杆菌是人及各种动物肠道中的正常菌群,食品中检出大肠杆菌意味着食品己经被污染。大肠杆菌作为各种食品的粪源性污染卫生细菌学指标,是国际上公认的卫生监测指示菌,因此大肠杆菌的检测技术显得十分重要,并相应出现了大量的大肠杆菌的各种检测方法。本研究阐述了大肠杆菌的几种检测方法,并与传统的检测技术进行了对比。     

食品中大肠杆菌生物检测方法的研究进展

大肠杆菌是人类及各种动物肠道中的正常寄居菌,一旦食品、饮用水被检测出含有E.coli就意味着食品可能直接或间接受到了粪便的污染.大肠杆菌是国际上公认的卫生监测指示菌.近年来,由于大肠杆菌引起的食品安全事件频发,严重危害人类健康,研发大肠杆菌快速检测以及防控技术具有重要意义.本文就近几年大肠杆菌感染引发的食品安全事件、生物检测技术等方面的论文做一综述.     

大肠杆菌快速检测研究进展

大肠杆菌是人及各种动物肠道中的正常寄居菌,食物或水中大肠杆菌的检出即意味着直接或间接的近期粪便污染。本文综述了几种大肠杆菌的快速检测法。     

屠宰工人、猪、分割肉、分割车间工用具中五种肠道病原菌带染情况调查

近年来,由空肠弯曲菌、小肠结肠炎耶尔森氏菌、致病性大肠杆菌所致的人类腹泻和食物中毒已引起了国际关注。沙门氏菌、志贺氏菌是目前腹泻和食物中毒的重要病原菌,也是我国《食品卫生法》(试行)规定的食品生产经营人员必检的肠道致病菌。耶尔森氏菌、空肠弯曲菌、沙门氏茵、大肠杆菌是人畜共患病的病原体。国内外对家禽家畜带菌情况作过不少调查,证实了猪是这些病原体的主要贮存宿主之一。但猪带上述肠道病菌、屠宰工人带菌、肉品污染的     

食品中大肠杆菌的检测方法分析

<正>肠杆菌作为一种寄居菌,是人和各类动物肠道中的一种正常的菌群,在人体内约占肠道菌中的1%。大肠杆菌属于革兰氏阴性短杆菌,特征是两端钝圆、能运动、无芽孢。大肠杆菌可以将维生素B和K合成,其在正常的栖居条件下是不会致病的。只有进入了胆囊、膀胱等处才可能造成炎症。如果在食品和饮用水中检测出了大肠杆菌,则表示这食品或饮用水有直接或间接的近期粪便污染。     

加拿大开发出可测病原菌的食品包装膜

加拿大一家公司研制开发出可测病原菌的食品包装膜，它利用以蛋白为基础的抗体来检测，该包装膜可以检测出沙门氏菌、大肠杆菌、李斯特菌等病原菌，当接触受到污染的食品时，即发生变色反应，从而确定有病菌污染，杜绝食品变质对人类的危害。     

消毒餐(饮)具大肠菌群指标不合格的原因分析

大肠菌群是指一类在一定培养条件下能够发酵乳糖、产酸产气的需氧或兼性厌氧革兰氏阴性无芽孢杆菌,在自然环境中广泛存在,直接或间接来源于人和温血动物的粪便。大肠菌群在食品安全领域是一项卫生质量指标,如果在食品或食品相关产品中检出,则意味着该食品或相关产品受到了人和温血动物的粪便污染。同时,由于大肠菌群与肠道致病菌来源相同,一般在外部环境中的生存时间与主要肠道病原菌一致,所以大肠菌群可同时作为肠道病原菌污染食品的指示菌。     

谨防乳肉制品中的新型高致病性大肠杆菌

正大肠杆菌是人和动物肠道中的正常栖居菌,一般为非致病菌,但大肠杆菌中某些血清型菌株具有高致病性,可引起腹泻,称为"致病性大肠杆菌"。产志贺毒素大肠杆菌产志贺毒素大肠杆菌就是一类高致病性食源性病原菌,包括大肠杆菌O26,以及O157、O45、O103、O104、O111、O121、O145等150多种其他血清型大肠杆菌。该菌为革兰氏阴性杆     

猪肉加工、流通过程中主要食源性病原细菌的监测

猪肉安全是食品安全的一个重要组成部分,食源性病原细菌是猪肉安全的重点监测对象。选择猪肉加工、流通过程的主要环节,应用PCR技术对沙门氏菌、产单核细胞李斯特菌、空肠弯曲菌、结肠弯曲菌和大肠杆菌O157等主要食源性病原细菌进行跟踪监测。结果表明:在所监测的6个环节中,均存在不同程度的病原菌污染,其中取内脏环节污染率最高,达49%;在监测的病原菌中,结肠弯曲菌的污染率最高,平均污染率为8.4%。取内脏、冷藏和销售环节是猪肉发生病原菌交叉污染的关键点。     

2009年嘉兴市食源性病原菌监测分析

目的监测2009年嘉兴市食品中致病菌污染状况。方法共采集275份生熟食品样品,分离沙门菌、单核细胞增生李斯特菌、大肠杆菌O157:H7、金黄色葡萄球菌和副溶血性弧菌。结果 75份生肉、水产品食源性病原菌总污染率45.3%,其中检出沙门菌6株,单核细胞增生李斯特菌12株,金黄色葡萄球菌4株,副溶血性弧菌18株。未检出大肠杆菌O157:H7。200份即食食品总污染率3.0%,以金黄色葡萄球菌污染为主。结论 2009年嘉兴市主要污染食品品种是冷藏冷冻生肉,污染的食源性致病菌以单核细胞增生李斯特菌和副溶血性弧菌为主。     

多重耐药与药物敏感大肠杆菌菌株在体外模拟胃肠道环境的生存力研究

目的 大肠杆菌是人和温血动物肠道重要的兼性厌氧寄居菌群, 也是水源和食品粪便污染指示菌。研究多重耐药型大肠杆菌和药物敏感型大肠杆菌菌株在体外模拟胃肠道环境下的生存能力, 本文数据为控制有害大肠杆菌提供理论依据。方法 从奎屯市超市采集30份零售食品, 分离出8份大肠杆菌阳性样品, 污染率为27%。利用纸片扩散法对分离的8株大肠杆菌进行耐药实验, 从8株菌中选出1株具有多重耐药的E27号菌和1株药物敏感型菌株E25号菌进行人工胃液和人工肠液耐受试验。结果 所测定的8株大肠杆菌对大多数耐药纸片敏感, 大肠杆菌对氨苄西林和四环素耐药率较高。8株菌中有4株耐药菌和4株敏感菌。结论 所选出的两株菌, E25在人工胃肠液中的耐受力较好, 菌株E27在人工胃肠液中耐受力较差, 敏感菌株E25要比多重耐药菌株E27菌数减少的缓慢。     

Fecal contamination and diarrheal pathogens on surfaces and in soils among Tanzanian households with and without improved sanitation

Little is known about the extent or pattern of environmental fecal contamination among households using low-cost, on-site sanitation facilities, or what role environmental contamination plays in the transmission of diarrheal disease. A microbial survey of fecal contamination and selected diarrheal pathogens in soil (n = 200), surface (n = 120), and produce samples (n = 24) was conducted in peri-urban Bagamoyo, Tanzania, among 20 households using private pit latrines. All samples were analyzed for E. coli and enterococci. A subset was analyzed for enterovirus, rotavirus, norovirus GI, norovirus GII, diarrheagenic E. coli, and general and human-specific Bacteroidales fecal markers using molecular methods. Soil collected from the house floor had significantly higher concentrations of E. coli and enterococci than soil collected from the latrine floor. There was no significant difference in fecal indicator bacteria levels between households using pit latrines with a concrete slab (improved sanitation) versus those without a slab. These findings imply that the presence of a concrete slab does not affect the level of fecal contamination in the household environment in this setting. Human Bacteroidales, pathogenic E. coli, enterovirus, and rotavirus genes were detected in soil samples, suggesting that soil should be given more attention as a transmission pathway of diarrheal illness in low-income countries.     

Microbial source tracking: state of the science

Although water quality of the Nation's lakes, rivers and streams has been monitored for many decades and especially since the passage of the Clean Water Act in 1972, many still do not meet the Act's goal of "fishable and swimmable". While waterways can be impaired in numerous ways, the protection from pathogenic microbe contamination is most important for waters used for human recreation, drinking water and aquaculture. Typically, monitoring methods used for detecting potential pathogenic microorganisms in environmental waters are based upon cultivation and enumeration of fecal indicator bacteria (i.e. fecal coliforms, E. coli, and fecal enterococci). Currently, there is increasing interest in the potential for molecular fingerprinting methods to be used not only for detection but also for identification of fecal contamination sources. Molecular methods have been applied to study the microbial ecology of environmental systems for years and are now being applied to help improve our waters by identifying problem sources and determining the effect of implemented remedial solutions. Management and remediation of water pollution would be more cost-effective if the correct sources could be identified. This review provides an outline of the main methods that either have been used or have been suggested for use in microbial source tracking and some of the limitations associated with those methods.     

Transmission of Common Foodborne Viruses by Meat Products

The most common foodborne viruses are single stranded RNA viruses which are adaptable and extremely resistant to environmental stress factors. Usual routes of food contamination are via stool material by persons shedding intestinal virus, or by saliva aerosols generated by shedding persons when coughing. Contamination of meat by animal viruses occurs when good hygienic and manufacturing practice fails. Once within food, viruses cannot replicate since they require living cells for this; hence food is not sensorily altered. Preventive measures in meat processing against pathogenic bacteria frequently have poor antiviral performance, while diagnostic techniques for viruses remain problematic.     

Relationship among fecal coliforms and <Emphasis Type="Italic"> Escherichia coli </Emphasis>in various foods

For much of the twentieth century, coliform bacteria and especially Escherichia coli have been used as indicators of possible post-processing contamination and the presence of E. coli as an indicator of fecal contamination in foods. In this study, 500 foods in 10 different groups, mainly dairy products, delicatessen products, salads, spices, cream cakes and fresh fruit and vegetable samples, were analyzed for the natural contamination of fecal coliforms and E. coli by the standard most probable number (MPN) method. The difference between weighted means of fecal coliforms and E. coli counts were only 0.246 log₁₀ MPN/g-ml (MPN/gram for solid samples, and MPN/milliliter for liquids). Enumeration results were also evaluated by Pearson's correlation coefficient ( r), Cronbach's alpha (f) and determination coefficient ( r ²) analysis. According to results, although 33 samples contained only non- E. coli fecal coliforms, the results of reliability analyses indicated that fecal coliform counts and E. coli counts may be used interchangeably ( P <0.0001). It can be said that fecal coliform or, preferably E. coli analysis is sufficient for rapid routine determination of fecal contamination, at least for those food groups analyzed in this research.     

Screening for enterocins and detection of hemolysin and vancomycin resistance in enterococci of different origins

The inhibitory activity of 122 out of 426 Enterococcus strains of geographically widespread origin and from different sources (food and feed, animal isolates, clinical and nonclinical human isolates) was tested against a wide range of indicator bacteria. Seventy-two strains, mainly belonging to the species Enterococcus faecium and Enterococcus faecalis were bacteriocinogenic. A remarkable variation of inhibitory spectra occurred among the strains tested, including inhibition of, for instance, only closely related enterococci, other lactic acid bacteria (LAB), food spoilage and pathogenic bacteria. No correlation could be found between the origin of the strains and the type of inhibitory spectrum, although a clustering of human isolates from both fecal and clinical origin was observed in the group of strains inhibiting lactic acid bacteria, Listeria, and either Staphylococcus or Clostridium. No relationship could be established between the presence of enterocin structural genes and the origin of the strain either, and hence no correlation seemed to exist between the presence of known enterocin genes and the activity spectra of these enterococci. The structural gene of enterocin A was widely distributed among E. faecium strains, whereas that of enterocin B only occurred in the presence of enterocin A. The vancomycin resistance phenotype as well as the presence of vancomycin resistance genes was also investigated. The vanA gene only occurred among E. faecium strains. The incidence of beta-hemolysis was not restricted to E. faecalis strains, but among the E. faecium strains the structural genes of cytolysin were not detected. beta-Hemolysis occurred in strains both from food and nonfood origin. It has been concluded that bacteriocin-producing E. faecium strains lacking hemolytic activity and not carrying cytolysin nor vancomycin resistance genes may be useful as starter cultures, cocultures, or probiotics.     

MICROBIOLOGICAL QUALITY OF BROILER CHICKEN CARCASSES PROCESSED HYGIENICALLY IN A SMALL SCALE POULTRY PROCESSING UNIT

Though large‐scale enterprises in highly‐developed countries often produce millions of items in a single day, world‐wide the volume of food produced in small‐scale enterprises or at home in countries still developing is of great economic importance and hygienic concern. Trials were conducted to determine the degree to which the sanitary state of broilers processed on a small scale could be improved through the application of simple hygienic practices. Dressed broiler chickens were examined for microbiological quality. Live birds carried high microbial load (log cfu/cm²): TPC 5.34; S. aureus 3.08 and fecal streptococci 3.02. The evisceration process resulted in a significant (P > 0.05) increase in microbial fecal contamination. Statistically significant lower microbial counts were observed in hygienically processed carcasses as compared with market carcasses. E. coli and fecal streptococci were completely absent in hygienically processed carcasses. Modest changes inprocessing methods resulted in broilers more hygienic with a gain in shelf‐life compared with those regularly available on the market.     

Coastal water quality impact of stormwater runoff from an urban watershed in southern California

Field studies were conducted to assess the coastal water quality impact of stormwater runoff from the Santa Ana River, which drains a large urban watershed located in southern California. Stormwater runoff from the river leads to very poor surf zone water quality, with fecal indicator bacteria concentrations exceeding California ocean bathing water standards by up to 500%. However, cross-shore currents (e.g., rip cells) dilute contaminated surf zone water with cleaner water from offshore, such that surf zone contamination is generally confined to < 5 km around the river outlet. Offshore of the surf zone, stormwater runoff ejected from the mouth of the river spreads out over a very large area, in some cases exceeding 100 km2 on the basis of satellite observations. Fecal indicator bacteria concentrations in these large stormwater plumes generally do not exceed California ocean bathing water standards, even in cases where offshore samples test positive for human pathogenic viruses (human adenoviruses and enteroviruses) and fecal indicator viruses (F+ coliphage). Multiple lines of evidence indicate that bacteria and viruses in the offshore stormwater plumes are either associated with relatively small particles (< 53 microm) or not particle-associated. Collectively, these results demonstrate that stormwater runoff from the Santa Ana River negatively impacts coastal water quality, both in the surf zone and offshore. However, the extent of this impact, and its human health significance, is influenced by numerous factors, including prevailing ocean currents, within-plume processing of particles and pathogens, and the timing, magnitude, and nature of runoff discharged from river outlets over the course of a storm.     

Beach sand and sediments are temporal sinks and sources of Escherichia coli in Lake Superior

The Duluth Boat Club (DBC) Beach, located in the Duluth-Superior harbor of Lake Superior, is frequently closed in summer due to high counts of Escherichia coli, an indicator of fecal contamination. However, the sources of bacteria contributing to beach closure are currently unknown. In this study, we investigated the potential sources of E. coli contaminating the DBC beach by using modified rep-PCR (HFERP) DNA fingerprinting. Over 3600 E. coli strains were obtained from 55 lake water, 25 sediment, and 135 sand samples taken from five transects at the DBC beach at 11 different times during the summer through fall months of 2004 and 2005. Potential sources of E. coli at this beach were determined by using a known-source DNA fingerprint library containing unique E. coli isolates from wildlife, waterfowl, and treated wastewater obtained near Duluth, MN. Amounts E. coli in the samples were enumerated by membrane filtration counting, and the presence of potentially pathogenic E. coli was determined by using multiplex PCR. E. coli counts in all samples increased during the summer and early fall (Julyto September). While E. coli in spring samples originated mainly from treated wastewater effluent, the percentage of E. coli from waterfowl increased from summer to fall. DNA fingerprint analyses indicated that some E. coli strains may be naturalized, and autochthonous members of the microbial community in the beach sand and sediments were examined. However, multiplex PCR results indicated that <1% of the E. coli strains at the DBC was potentially pathogenic. Our results also suggest that wave action may influence the early colonization and homogeneous distribution of E. coli in beach sand and the subsequent release of sand or sediment-borne E. coli into lake water. Taken together, these results indicate that sand and sediment serve as temporal sources and sinks of human and waterfowl-derived E. coli that contribute to beach closures.