A cluster of Escherichia coli O157: nonmotile infections associated with recreational exposure to lake water

OBJECTIVES: To identify cases and determine risk factors for an outbreak of Escherichia coli (E. coli) O157: nonmotile (NM) infections in children attending a summer day care program in California. METHODS: The authors conducted a retrospective cohort study; the cohort comprised first and second graders who attended the day care program during the last week in August 1999. Shiga toxin testing and molecular subtyping using pulsed-field gel electrophoresis were performed on isolates. Lake water, lake bottom sediment samples, and waterfowl feces from the lake environs were cultured for E. coli O157. RESULTS: Three cases of Shiga toxin-producing E. coli O157: NM infections with matching pulsed-field gel electrophoresis patterns and four probable cases were found. Children who swallowed more than a mouthful of water had a higher attack rate than those who swallowed less than a mouthful or none at all (43% vs. 10%, relative risk = 4.43, 95% confidence interval 1.12, 17.50). CONCLUSIONS: E. coli O157: NM infections were associated with swallowing water from a freshwater lake. Potential sources of contamination include feces from humans, cattle, or deer. This outbreak illustrates the value in screening patients with diarrhea for E. coli O157, submitting isolates to public health laboratories, and using molecular techniques to identify related cases. Outbreaks associated with contaminated freshwater could be averted by prevention and early detection of contamination.     

Isolation and characterization of enterohaemorrhagic Escherichia coli O157:1H7 from cattle in Belgium and Poland

EHEC O157 were isolated from faeces of Belgian and Polish beef slaughter cattle. In Belgium, 1281 faecal samples were analysed by immunomagnetic separation [IMS] after enrichment in buffered peptone water from June 1998 till July 1999. Eighty-one samples (6.3%) were positive for E. coli O157. Phage type 8 was most frequently found. Bulls between 1 and 2 years old, slaughtered in September and October were most frequently found positive. Atypical biochemical features were observed in some isolates: 22 (27%) isolates were urease positive and 1 (1.2%) isolate was unable to ferment lactose. In Poland, 551 faecal samples, taken from January 1999 till December 1999, were examined using exactly the same techniques. Four faecal samples (0.7%) were positive for O157 EHEC, yielding seven phage type 8 isolates. All positive samples were from cattle younger than 2 years. Positive samples occurred in August, September and October.     

东台市肠出血性大肠埃希菌O157感染监测

目的为掌握肠出血性大肠埃希菌O157在东台市家禽、家畜中的带菌,腹泻病人中的感染和自来水厂水源水中的污染情况.方法2000-2002年,分别在流行季节采集家禽、家畜和腹泻病人粪便及自来水厂水源水,应用免疫磁珠浓集、山梨醇麦康凯平板分离、生化和血清学反应进行鉴定.结果3年间东台市采集的6种动物粪便有4种中检出肠出血性大肠埃希菌O157,其阳性率牛为11.32%、羊为10.58%、猪为9.35%、鸡为7.73%.腹泻病人的阳性率为1.57%.采集的178份自来水厂水源水、60只苍蝇标本中均未分离出肠出血性大肠埃希菌O157.3株自动物粪便分离株具有至少2种混合型毒力基因.75株肠出血性大肠埃希菌O157菌株对15种抗生素存在不同的耐药率.结论东台市家禽、家畜和腹泻病人中存在肠出血性大肠埃希菌O157感染,且存在流行的潜在危险.     

An outbreak of E. coli O157 infection with evidence of spread from animals to man through contamination of a private water supply

An outbreak of E. coli O157 infection occurred in the Highland Region of Scotland in the summer of 1999. The source of the outbreak was traced to an untreated private water supply. All six cases identified arose in visitors to the area, and most had very limited exposure to the contaminated water. Permanent residents on the same supply were unaffected. The E. coli O157 isolates from the water, sheep faeces collected from around the source and the human stool samples were indistinguishable using pulsed field gel electrophoresis. Previously reported outbreaks of E. coli O157 linked to potable water supplies have resulted from structural or treatment failures, which allowed faecal contamination of source water. Here, contamination of the water supply and subsequent human infection was due to the use of an untreated, unprotected private water source in a rural area where animals grazed freely.     

Meningococcal disease at the University of Southampton: outbreak investigation

Between November 1992 and February 1993, a large outbreak of Escherichia coli O157:H7 infections occurred in the western USA and was associated with eating ground beef patties at restaurants of one fast-food chain. Restaurants that were epidemiologically linked with cases served patties produced on two consecutive dates; cultures of recalled ground beef patties produced on those dates yielded E. coli O157:H7 strains indistinguishable from those isolated from patients, confirming the vehicle of illness. Seventy-six ground beef patty samples were cultured quantitatively for E. coli O157:H7. The median most probable number of organisms was 1.5 per gram (range, < 0.3-15) or 67.5 organisms per patty (range, < 13.5-675). Correlation of the presence of E. coli O157:H7 with other bacterial indicators yielded a significant association between coliform count and the presence of E. coli O157:H7 (P = 0.04). A meat traceback to investigate possible sources of contamination revealed cattle were probably initially colonized with E. coli O157:H7, and that their slaughter caused surface contamination of meat, which once combined with meat from other sources, resulted in a large number of contaminated ground beef patties. Microbiological testing of meat from lots consumed by persons who became ill was suggestive of an infectious dose for E. coli O157:H7 of fewer than 700 organisms. These findings present a strong argument for enforcing zero tolerance for this organism in processed food and for markedly decreasing contamination of raw ground beef. Process controls that incorporate microbiological testing of meat may assist these efforts.     

Reduction of Escherichia coli O157:H7 in cattle drinking-water by trans-cinnamaldehyde

Cattle serve as a major reservoir of E. coli O157:H7 and excrete the pathogen in feces. Environmental persistence of E. coli O157:H7 plays a vital role in its epidemiology on farms, and cattle water troughs are a demonstrated long-term reservoir of E. coli O157:H7 for animals. The objective of this study was to investigate the potential of low concentrations of trans-cinnamaldehyde for killing E. coli O157:H7 in cattle drinking-water. A five-strain mixture of E. coli O157:H7 was inoculated (at approximately 8.0 log colony-forming units [CFU]/mL) into 100 mL samples of well water containing 0, 0.03, 0.05, 0.07, or 0.1% trans-cinnamaldehyde. Additionally, water samples containing (1% w/v) bovine feces or feed were also included. The samples were incubated at 21 degrees , 8 degrees , or 4 degrees C for 7 days and tested for viable E. coli O157:H7 on days 0, 1, 3, 5, and 7. Triplicate samples of each treatment and control were included and the study was replicated twice. All concentrations of trans-cinnamaldehyde were effective in killing E. coli O157:H7 in water, but the magnitude of killing significantly increased with increase in trans-cinnamaldehyde concentration and storage temperature (p < 0.05). The presence of feed or feces in water decreased the antibacterial effect of trans-cinnamaldehyde on E. coli O157:H7 (p < 0.05). This study indicated that trans-cinnamaldehyde is effective in killing E. coli O157:H7 in cattle drinking-water, but detailed palatability studies on cattle intake of water containing the antimicrobial are needed.     

Cattle as a possible source of verocytotoxin-producing Escherichia coli O157 infections in man.

In May-June 1992 cases of infection with verocytotoxin-producing (VT+) Escherichia coli O157 in South Yorkshire could have been associated with prior consumption of beef from a local abattoir. During investigation of the abattoir, bovine rectal swabs and samples of meat and surface swabs from beef carcasses were examined for E. coli O157, isolates of which were tested for toxigenicity, plasmid content and phage type. E. coli O157 was isolated from 84 (4%) of 2103 bovine rectal swabs; of these 84, 78 (93%) were VT+, the most common phage types being 2 and 8, the types implicated in the cluster of human cases. Positive cattle were from diverse sources within England. E. coli O157 was isolated from 7 (30%) of 23 carcasses of rectal swab-positive cattle and from 2 (8%) of 25 carcasses of rectal swab-negative cattle. The study has shown that cattle may be a reservoir of VT+ E. coli O157, and that contamination of carcasses during slaughter and processing may be how beef and beef products become contaminated and thereby transmit the organism to man.     

Use of rope devices to describe and explain the feedlot ecology of Escherichia coli O157:H7 by time and place

Escherichia coli O157:H7 is an important pathogen of humans, and cattle populations serve as an important reservoir for human exposure. The organism is ubiquitous to feedlot cattle populations, although the nature of its occurrence is quite dynamic. Why E. coli O157:H7 varies by time and place in fed cattle is poorly understood. This study was designed to describe and explain the occurrence of E. coli O157:H7 by pen-level factors of time and place. From each pen, we cultured seven ropes placed within pens for cattle to rub and chew (ROPES), in order to classify the pens as high or low prevalence in longitudinal studies conducted during the summer and winter feeding periods of 2 full years. We observed differences in occurrence of ROPES-positive pens by season, weeks within season, and feedyard. ROPES-positive pens clustered temporally. Factors associated with ROPES-positive pen-weeks during both the summer and winter feeding periods were feedyard, prior 7-day mean air temperature, recovery of E. coli O157:H7 from the composite fecal sample, and recovery of E. coli O157:H7 from the water tank. Pens of summer-fed cattle were less likely to be ROPES-positive for E. coli O157:H7 if the ROPES were positive for Salmonella spp. The condition of the pen surface was associated with the likelihood for winter-fed pens of cattle to be ROPES-positive. We were able to monitor these pens of cattle using ROPES at minimal cost and without disturbing individual cattle. These observations improve our understanding of the ecology of E. coli O157:H7 in fed cattle, and also illustrate the importance of designing and analyzing observational studies and clinical trials to account for time- and place-dependent variables that affect the probability of detecting E. coli O157:H7.     

RAPD在大肠埃希菌O157同源性分析中的应用

目的:研究腹泻病人和食品中分离出的大肠埃希菌O157的分子特征,为O157菌株的流行病学溯源和疫情控制提供有效手段。方法:采用随机引物扩增多态性DNA分析(randomly amplified polymorphic DNA analysis,RAPD)对10株O157菌株进行基因分型。结果:10株菌聚类为3个类群,分属于三个不同的克隆。结论:RAPD技术可用于O157菌株的流行病学调查和溯源。     

Swimming-associated outbreak of Escherichia coli O157:H7

In 1997 the first outbreak of Escherichia coli O157:H7 infections involving 14 cases occurred in Finland. A case was defined as a resident of Alavus with an episode of diarrhoea between 5 and 17 July 1997, and from whom E. coli O157:H7 was isolated from stool. The investigation included case searching and a population-based case control study. Five primary and eight symptomatic secondary cases of E. coli O157:H7 illness were detected. In the 10 days before the outbreak, all 5 primary patients (aged 3-8 years), but only 6 of 32 population controls from the same age range (Fisher's test, P < 0.001) and 4 of 10 sibling controls (P < 0.05) had visited (but had not necessarily bathed in) a shallow beach popular among young children. Four out of 5 primary cases had remained within 5 m of the beach while swimming and had swallowed lake water compared to 1 of 5 population controls. These analytical epidemiologic findings incriminated fresh lake water as the vehicle of E. coli O157:H7 transmission.     

衢州市2000-2009年肠出血性大肠埃希菌O157∶H7监测

目的了解浙江省衢州市肠出血性大肠埃希菌O157∶H7人的感染、食品污染以及动物和媒介昆虫带菌情况。方法在流行季节采集腹泻患者、动物粪便以及各类食品、苍蝇等样本,MEC肉汤增菌后,用特异性免疫磁珠集菌,以科玛嘉显色平板分离,纯化的菌株进行生化鉴定、血清分型及毒力基因检测。结果 2000-2009年,共检测样本12 292份,检出EHEC O157∶H7 19株,总检出率为0.15%。其中4种宿主动物粪便样本中检出18株,检出率分别为羊2.14%、牛1.29%、猪0.45%、鸭0.19%;食品中从生猪肉中检出1株,检出率0.17%;腹泻患者和苍蝇样本中均未检出。经毒力基因检测,其中16株stx2+hly+eaeA阳性,1株hly+eaeA阳性,其余2株不带毒力基因,带毒率89.47%。结论浙江省衢州市部分动物中产毒的EHEC O157∶H7带菌率较高,表明该地区存在暴发或流行的潜在危险,应加强综合监测。     

Escherichia coli O157:H7 diarrhoea associated with well water and infected cattle on an Ontario farm.

A 16-month old female child living on an Ontario dairy farm was taken to hospital suffering from bloody diarrhoea. Escherichia coli O157:H7 was isolated from her stool. Initial tests of well water samples were negative for E. coli by standard methods but culture of selected coliform colonies on sorbitol-MacConkey agar led to isolation of E. coli O157:H7. E. coli O157:H7 was also isolated from 63% of cattle on the farm. The E. coli O157:H7 isolates from the child, the water and the cattle were phage type 14, produced verotoxins 1 and 2, and were highly related on analysis by pulsed field gel electrophoresis. The child did not have known direct contact with the cattle and did not consume unpasteurized milk. Hydrogeological investigation revealed the design and location of the well would allow manure-contaminated surface water to flow into the well. This investigation demonstrates that cattle farm well water is a potential source of E. coli O157:H7 which may not be identified by standard screening for E. coli in water.     

Molecular typing methods to investigate transmission of Escherichia coli O157:H7 from cattle to humans.

The utility of phage typing, pulsed-field gel electrophoresis (PFGE), and plasmid profile analysis was compared, to differentiate between Canadian Escherichia coli O157:H7 strains of human (n = 27) and cattle (n = 24) origin. The diversity indices for phage typing, plasmid analysis and PFGE were 0.85, 0.69 and 0.93, respectively. PFGE and phage typing were also applied to study the role of direct transmission of E. coli O157:H7 from cattle to humans on isolates collected from two separate farm outbreaks. PFGE showed that more than one E. coli O157:H7 strain with varying PFGE DNA subtype profiles, may be responsible for an outbreak, and that more than one E. coli O157:H7 subtype may be circulating on a particular farm at any one time. To our knowledge, this is one of the first reports where PFGE typing was used to verify the direct transmission of E. coli O157:H7 from cattle to humans.     

江苏省淮北地区肠出血性大肠埃希菌O157:H7感染性腹泻并发急性肾衰的研究

目的 了解1999～2000年江苏省淮北部分地区发生肠出血性大肠埃希菌O157:H7感染性腹泻并发急性肾衰病例的病因与流行特点。方法 运用流行病学、微生物学、分子生物学等方法,对传染源、传播途径、流行因素进行调查和分析。结果 1999年共在9个县(区)报告肠出血性大肠埃希菌O157:H7感染性腹泻并发急性肾衰病例95例,死亡83例,病死率87.37％。6月中、下旬为发病高峰,男女之比为1:1.44,年龄以50岁以上为主,占88.42％。2000年发生38例,死亡34例,病死率89.47％。引起爆发的主要危险因素有不饮自来水、吃剩饭菜、厨房卫生差、生食瓜果和饭前便后不洗手。从2例重症患者及3例腹泻患者粪便标本分离到O157:H7;宿主动物O157:H7携带率为9.62％(170/1767),菌株毒力基因阳性率达99.41％(169/170)。从患者粪便标本分离的菌株与家禽家畜分离的菌株属同一克隆群。结论 这是中国首次发现由O157:H7引起的爆发疫情,其发生与宿主动物带菌率高且菌株毒力基因阳性率高有密切关系,引起疫情的具体传播途径复杂多样,主要的感染危险因素与个人卫生、家庭卫生不良有关。     

A statewide outbreak of Escherichia coli O157:H7 infections in Washington State

In November 1986, a statewide outbreak of Escherichia coli O157:H7 infections in Washington State was identified after a physician in an eastern Washington community hospitalized three patients with hemorrhagic colitis which progressed to thrombotic thrombocytopenic purpura. Epidemiologic investigation identified 37 cases in this community and linked the illnesses to a local restaurant which had served ground beef that was the suspected initial vehicle of transmission. The plasmid profile and toxin production pattern (Shiga-like toxin II alone) of the outbreak strain provided a unique strain marker. E. coli O157:H7 infections caused by this strain were simultaneously seen in other parts of the state among nursing home residents and in patients with the hemolytic-uremic syndrome, and an increase in sporadic cases of hemorrhagic colitis was noted at a Seattle health maintenance organization. It is suspected that a contaminated product, probably ground beef distributed statewide, was the common source. Tracing of this meat led to farms where rectal swabs from six (1%) of 539 cattle tested yielded E. coli O157:H7, although the plasmids and toxin production patterns of these isolates differed from the human outbreak strain. Introduction of a single strain of E. coli O157:H7 has the potential to cause widespread concurrent outbreaks. Such outbreaks are likely to escape recognition until heightened screening and surveillance for E. coli O157:H7 is established.     

Screening policies for daycare attendees: lessons learned from an outbreak of E. coli O157:H7 in a daycare in Waterloo, Ontario

OBJECTIVES: Control measures for enteric outbreaks in child care settings frequently include screening by stool cultures from symptomatic children only. We present evidence from an investigation of Escherichia coli (E. coli) O157:H7 in a daycare in Waterloo, Ontario to support implementation of a mandatory screening policy for all children during an outbreak. METHODS: In addition to routine outbreak control measures employed by the health unit, stool samples from all children and staff were collected, with positive E. coli cultures typed by pulsed field gel electrophoresis (PFGE). We conducted a cohort study, using data from the environmental investigation and questionnaires administered to parents and staff, to look for risk factors for infection and to survey parent/staff knowledge regarding appropriate management of diarrhea. RESULTS: Overall 11 E. coli O157:H7 cases were identified (7 lab-confirmed); 9 were children. No common source of infection was identified. Factors identified as possibly contributing to person-to-person transmission within the daycare included: i) the underreporting and possible attendance of symptomatic children despite alerting parents to the outbreak and requirements to keep symptomatic children at home, ii) possible transmission from an asymptomatic infected child, and iii) inconsistent understanding among parents and staff regarding diarrhea and appropriate management of a child with diarrhea. DISCUSSION/CONCLUSION: This investigation reveals that in child care settings, E. coli O157:H7 outbreak screening policies based on reported symptoms only may be insufficient. We recommend that such policies be amended to include the collection of at least one stool culture from all children in attendance, regardless of symptom history.     

Differences in survival of Escherichia coli O157:H7 under various conditions that re-enact the cooking of lunches implicated in an outbreak of haemorrhagic diarrhoea

Two elementary schools were served lunches that were cooked in the same kitchen. An outbreak of Escherichia coli O157:H7 occurred at one school where the dishes that were prepared for the school were lukewarm and kept for 33 min at an average temperature of 45 degrees C before serving. However, no outbreak occurred at the other school where dishes were hot and were kept for 60 min at an average temperature of 50 degrees C before serving. In a series of experiments on the survival of E. coli O157:H7 in the liquid portion of similarly prepared food, the population of E. coli O157:H7 was reduced by 10-3 by heating at 50 degrees C for 60 min and by only 10-1 by heating at 45 degrees C for 40 min. Further, E. coli O157:H7 survived at 45 degrees C for 40 min but not at 50 degrees C for 60 min at pH 4.0 with a 4.0% salt concentration that was similar to that of the liquid part of the food. These results indicate that pH and salt concentration of cooked food markedly affect the survival of E. coli O157:H7 and help to explain the occurrence of the disease outbreak at only one of the schools.     

An outbreak of E. coli O157:H7 hemorrhagic colitis associated with unpasteurized gouda cheese

BACKGROUND: A cluster of E. coli O157:H7 hemorrhagic colitis was identified in metro Edmonton, Alberta through notifiable disease surveillance in late 2002. METHODS: Environmental health officers collected food histories and clinical information from cases in the cluster. The provincial public health laboratory conducted pulsed field gel electrophoresis (PFGE) analysis on E. coli O157:H7 isolates from cluster cases. Public health and food regulatory agencies conducted an investigation when a food source (unpasteurized gouda cheese) was implicated. RESULTS: PFGE analysis revealed an "outbreak" profile in 13 cases. Onset dates for the outbreak cases ranged between October 2002 and February 2003. Two cases, aged 22 months and 4 years, developed hemolytic uremic syndrome as a result of their infection. Consumption of unpasteurized gouda cheese produced at a local dairy farm was reported by 12 of 13 outbreak cases in the 2 to 8 days prior to illness. E. coli O157:H7 was isolated from 2 of 26 cheese samples manufactured by the implicated producer. The cheese isolates had indistinguishable PFGE profiles as compared with outbreak case isolates. Implicated cheese was found to be contaminated with E. coli O157:H7 104 days after production, despite having met regulated microbiological and aging requirements. CONCLUSION: To our knowledge, this is the first confirmed outbreak of E. coli O157:H7 infection in Canada associated with raw milk hard cheese. A review of federal legislation vis-à-vis raw milk hard cheese may be in order.     

Community-wide outbreak of Escherichia coli O157:H7 associated with consumption of frozen beef burgers

On 24-25 October 2005 a cluster of five haemolytic uraemic syndrome (HUS) cases was reported in southwest France. An investigation was undertaken to identify the outbreak source and implement control measures. Cases were defined as individuals with HUS or diarrhoea with isolation of Escherichia coli O157:H7 in stools or a positive antibody response to E. coli O157 lipopolysaccharide, resident in southwest France with symptom onset after 19 September 2005. Sixty-nine identified patients had symptom onset between 5 October and 3 November 2005, including 17 cases of HUS. One brand of frozen beef burgers produced on 22 August 2005 was consumed by all patients in the week before symptom onset. E. coli O157:H7 strains from patients, patients' burgers and the manufacturing plant were genetically related. This is the largest community-wide outbreak of E. coli O157:H7 in France to date and the first associated with consumption of contaminated frozen beef burgers.     

Immunomagnetic separation as a sensitive method for isolating Escherichia coli O157 from food samples.

Minced beef samples inoculated with Escherichia coli O157 were cultured in buffered peptone water supplemented with vancomycin, cefsulodin and cefixime (BPW-VCC) and subcultured to cefixime tellurite sorbitol MacConkey (CT-SMAC) agar both directly and after immunomagnetic separation (IMS) of the organism with magnetic beads coated with an antibody against E. coli O157 (Dynabeads anti-E. coli O157, Dynal, Oslo). E. coli O157 was recovered from initial inocula of 200 organisms/g by direct subculture and 2 organisms/g by IMS. Twelve strains of E. coli O157 of different combinations of phage type, H antigen and toxin genotype were all recovered from initial inocula of two organisms/g by IMS. Non-specific binding of other organisms to the magnetic beads could be reduced by washing of the beads in PBS with Tween-20 0.002-0.005% E. coli O157 was not bound by magnetic coated with an unrelated antibody. During investigation of a dairy herd that was possibly linked to a small outbreak of infection with E. coli O157, the organism was isolated from 2 of 279 forestream milk samples from individual cattle; both isolates were made only by the IMS technique. IMS is rapid, technically simple, and a specific method for isolation of E. coli O157 and will be useful in epidemiological studies.