The role of heightened surveillance in an outbreak of Escherichia coli O157.H7.

After instituting laboratory screening for Escherichia coli O157.H7, a Connecticut hospital isolated the organism from four persons in September 1993. As a result, an outbreak of E. coli O157.H7 associated with a country club was detected. The club had served hamburger from the same shipment at two picnics. Attendees of two picnics were interviewed, stool cultures were obtained from symptomatic persons, and the remaining hamburger was cultured. Twenty (22%) of 89 persons who ate hamburger became ill, compared with 1 of 60 who did not eat hamburger (relative risk = 13.5, 95% confidence interval 3.2-56.3). Among persons who ate hamburgers, illness was strongly associated with eating hamburger that was not thoroughly cooked (P < 0.001). All 20 samples from 5 remaining boxes of patties yielded E. coli O157.H7. Isolates from hamburger and case-patients were indistinguishable by pulsed-field gel electrophoresis. Heightened surveillance can rapidly identify outbreaks and may mitigate their impact. However, continued review of food safety issues is necessary if E. coli O157.H7 outbreaks are to be prevented.     

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.     

First recognized community outbreak of haemorrhagic colitis due to verotoxin-producing Escherichia coli O 157.H7 in the UK

The first recognized outbreak of haemorrhagic colitis due to Escherichia coli O 157.H7 in the United Kingdom affected at least 24 persons living in East Anglia over a 2-week period. The illnesses were characterized by severe abdominal pain and bloody diarrhoea of short duration. Eleven patients were admitted to hospital and there was one death. Patients were mainly adult women who had not eaten out of the home in the 2 weeks before onset. Unlike previously reported outbreaks hamburgers were not the vehicle of infection, and a case-control study suggested that handling vegetables, and particularly potatoes, was the important risk factor.     

Factors contributing to the emergence of Escherichia coli O157 in Africa.

In 1992, a large outbreak of bloody diarrhea caused by Escherichia coli O157 infections occurred in southern Africa. In Swaziland, 40,912 physician visits for diarrhea in persons ages >5 years were reported during October through November 1992. This was a sevenfold increase over the same period during 1990-91. The attack rate was 42% among 778 residents we surveyed. Female gender and consuming beef and untreated water were significant risks for illness. E. coli O157:NM was recovered from seven affected foci in Swaziland and South Africa; 27 of 31 patient and environmental isolates had indistinguishable pulsed-field gel electrophoresis patterns. Compared with previous years, a fivefold increase in cattle deaths occurred in October 1992. The first heavy rains fell that same month (36 mm), following 3 months of drought. Drought, carriage of E. coli O157 by cattle, and heavy rains with contamination of surface water appear to be important factors contributing to this outbreak.     

Escherichia coli O157:H7 outbreak linked to salami, British Columbia, Canada, 1999

An outbreak of E. coli O157:H7 infections was identified in November 1999 with a fivefold increase in the occurrence of laboratory-confirmed cases of E. coli O157:H7 infection. A matched case-control study was conducted. Samples of food from cases and from retailers were analysed for the presence of E. coli O157:H7. A total of 143 cases were identified over a 12-week period with the same pulsed-field gel electrophoresis (PFGE) pattern. The case-control study found that Company A salami was significantly associated with illness (Mantel-Haenszel matched odds ratio 10.0%, 95% CI 1.4-434, P=0.01). Company A salami tested positive for E. coli O157:H7 and isolates had the same PFGE pattern as case isolates. An immediate voluntary national recall of Company A dry fermented meat products took place. Findings from the investigation of this outbreak suggest that the hold-and-test option may not be adequate to prevent shiga-toxigenic Escherichia coli (STEC) infection in salami consumers.     

徐州市2000年肠出血性大肠埃希菌O157：H7感染性腹泻的调查

目的 了解徐州市丰县和铜山县肠出血性大肠埃希菌（EHEC）O157：H7引起的出血性结肠炎（HC）在腹泻病患者中所占的比例，以及临床症状和肾功能变化的情况。方法 使用EHECO157胶体金快速检测试剂筛选粪便标本，阳性者使用免疫磁珠方法分离病原菌。对经过细菌学证实的EHECO157：H7引起的HC患者，进行临床症状的观察和生化检验指标分析。结果 2000年5月份，丰县由EHECO157：H7引起的HC占腹泻病患者0.98%，6月份铜山县的HC患者占腹泻病患者5.89%。在出现腹泻病症状的同时，18.5%患者的肾功能已经出现异常，表现为尿蛋白，血清肌苷或血尿素氮等指标的升高，在27例HC患者中，有14和13例分别分离到不产生志贺毒素和产生志贺毒素的EHECO157：H7菌株，根据分离菌株是否产生志贺毒素将患者分为两组进行比较，尿蛋白阳性患者的比例分别为4/13和1/14，血小板减少患者的比例分别为6/13和3/14，统计学分析有显著意义。提示分离到产生志贺毒素的EHECO157：H7菌株的患者，发生肾功能异常的可能性较大，结论 此次调查证实了EHECO157：H7感染所引起的HC在整个腹泻病患者中所占的比例随季节的变化而不同，感染产生志贺毒素EHECO157：H7菌株的患者，发生肾功能异常的可能性要比不产生志贺毒素的大，还证实了在该菌感染的初期，患者的肾功能就已经出现了异常。     

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.     

Enteroaggregative E. coli O104 from an outbreak of HUS in Germany 2011, could it happen again?

Enterohaemorrhagic E. coli (EHEC) particularly O157:H7 (Sequence type 11 complex), is the best documented and most well-known of E. coli that cause diarrhoea. The importance of EHEC lies in the severity of disease. Outbreaks can infect thousands of people causing bloody diarrhoea and haemolytic uremic syndrome (HUS) that in turn can result in protracted illness or even death. The ability of EHEC to colonise the human gut is normally associated with the presence of genes from another group of diarrhoeagenic E. coli, the enteropathogenic E. coli (EPEC), via the locus of enterocyte effacement. However, the massive outbreak in Germany was caused by an EHEC which had acquired virulence genes from yet another group of diarrhoeagenic E. coli, the enteroaggregative E. coli (EAEC). In reality EAEC is probably the most common bacterial cause of diarrhoea but is not identified in most diagnostic laboratories. This outbreak emphasises the importance of being able to detect all diarrhoeagenic E. coli and not to focus on E. coli O157:H7 alone. Routine surveillance systems for EAEC, a once ignored global pathogen, would go a long way to reaching this goal. This review describes methods for identifying non-O157 EHEC and describes the key genetic features of EHEC and EAEC. Our aim is to provide information for laboratories and policy makers which enables them to make informed decisions about the best methods available for detecting newly emergent strains of diarrhoeagenic E. coli.     

Virulence profiling and quantification of verocytotoxin-producing Escherichia coli O145:H28 and O26:H11 isolated during an ice cream-related hemolytic uremic syndrome outbreak

In September-October 2007, a mixed-serotype outbreak of verocytotoxin-producing Escherichia coli (VTEC) O145:H28 and O26:H11 occurred in the province of Antwerp, Belgium. Five girls aged between 2 and 11 years developed hemolytic uremic syndrome, and seven other coexposed persons with bloody diarrhea were identified. Laboratory confirmation of O145:H28 infection was obtained for three hemolytic uremic syndrome patients, one of whom was coinfected with O26:H11. The epidemiological and laboratory investigations revealed ice cream as the most likely source of the outbreak. The ice cream was produced at a local dairy farm using pasteurized milk. VTEC of both serotypes with indistinguishable pulsed-field gel electrophoresis patterns were isolated from patients, ice cream, and environmental samples. Quantitative analysis of the ice cream indicated concentrations of 2.4 and 0.03 CFU/g for VTEC O145 and O26, respectively. Virulence typing revealed that the repertoire of virulence genes carried by the O145:H28 outbreak strain was comparable to that of O157 VTEC and more exhaustive as compared to the O26:H11 outbreak strain and nonrelated clinical strains belonging to these serotypes. Taken together, these data suggest that O145:H28 played the most important role in this outbreak.     

An epidemic of bloody diarrhea: Escherichia coli O157 emerging in Cameroon?

Between November 1997 and April 20, 1998, bloody diarrhea sickened 298 persons in Cameroon. Laboratory investigation of the epidemic (case-fatality rate, 16.4%) documented amoebiasis in one of three patients and three types of pathogens: multidrug-resistant Shigella dysenteriae type 1, S. boydii, and enterohemorrhagic Escherichia coli. We report the first isolation of E. coli O157:H7 in Cameroon and the second series of cases in the Central African region.     

An outbreak of Escherichia coli O157:H7 infections and haemolytic uraemic syndrome associated with consumption of unpasteurized apple cider

During October 1996, an outbreak of Escherichia coli O157:H7 infections among Connecticut residents occurred. An epidemiologic investigation included enhanced surveillance and a case-control study. Clinical isolates of Escherichia coli O157:H7 were typed by pulsed-field gel electrophoresis (PFGE). Implicated cider samples were analysed by culture and polymerase chain reaction (PCR). Consumption of implicated cider was associated with illness; (matched odds ratio = undefined, 95 % confidence interval = 3.5-infinity). Ultimately, a total of 14 outbreak-associated patients were identified. All isolates analysed by PFGE yielded the outbreak-associated subtype. Escherichia coli O157:H7 was not cultured from three cider samples; PCR analysis detected DNA fragments consistent with Escherichia coli O157:H7 in one. This outbreak was associated with drinking one brand of unpasteurized apple cider. PFGE subtyping supported the epidemiologic association. PCR analysis detected microbial contaminants in the absence of live organisms. Washing and brushing apples did not prevent cider contamination.     

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.     

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.     

Importance of culture confirmation of shiga toxin-producing Escherichia coli infection as illustrated by outbreaks of gastroenteritis--New York and North Carolina, 2005

Escherichia coli O157:H7 and other strains of E. coli that produce Shiga toxin are collectively known as Shiga toxin-producing E. coli (STEC). The current outbreak of STEC O157 infections associated with eating fresh spinach illustrates the importance of obtaining isolates to identify the source of the infections. Laboratory methods that do not require bacterial culture of stool specimens to identify STEC are being used increasingly by clinical diagnostic laboratories, sometimes without subsequent confirmation of a strain by isolating it in culture. This report describes findings from outbreaks of gastroenteritis in 2005 in New York and North Carolina in which clinical diagnostic laboratories initially used only non-culture methods to detect Shiga toxin (Stx). The findings highlight the importance of confirmation of Stx-positive stool specimens by bacterial culture for timely and reliable identification of STEC infections, including E. coli O157 and non-O157 STEC, to enable implementation of appropriate public health actions. An important part of that identification is determining the serotype of all STEC isolates and the subtype of STEC O157 strains so that outbreaks can be detected and traced back to sources.     

2007年浙江省衢州地区动物中产志贺毒素大肠埃希菌O157:H7感染状况

目的:了解2007年浙江省衢州地区产志贺毒素大肠埃希菌O157:H7在动物中的分布情况及其耐药性、PFGE分型及毒力基因携带状况。方法:按全国O157:H7监测方案于5~10月份肠道传染病高发季节,在衢州地区采集各种动物粪便/肛拭,用免疫磁珠富集后进行O157:H7分离培养、鉴定,可疑菌株以PCR法检测O、H抗原及志贺样毒素(SLT1和SLT2)、粘附抹平因子(eaeA)及溶血素(hly)4种毒力基因。用脉冲场凝胶电泳(pulse field gel electrophoresis,PFGE)方法进行同源性分析,同时选择14种抗生素进行药敏试验,分析分离所得菌株的耐药状况。结果:共监测动物粪便标本300份,分离得产志贺毒素大肠埃希菌O157:H7菌株16株,分离率为5.33%。16株O157:H7菌株,毒力基因Hly、eaeA、SLT2均阳性,SLT1均阴性。脉冲场凝胶电泳分型显示,16株O157:H7菌株可分2个PFGE基因型,型间差异较小。耐药性分析显示这些菌株对红霉素、利福平的耐药率最高,达100.0%,对其他受试抗生素均敏感。结论:该地区动物中产志贺毒素大肠埃希菌O157:H7带菌率较高,所分离菌株主要携带SLT2基因,因此推测该地区存在发生产志贺毒素大肠埃希菌O157:H7感染暴发或流行的潜在危险,需增加对动物源性O157:H7的监测力度。     

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 multistate outbreak of Escherichia coli O157:H7 infections linked to alfalfa sprouts grown from contaminated seeds.

A multistate outbreak of Escherichia coli O157:H7 infections occurred in the United States in June and July 1997. Two concurrent outbreaks were investigated through independent case-control studies in Michigan and Virginia and by subtyping isolates with pulsed-field gel electrophoresis (PFGE). Isolates from 85 persons were indistinguishable by PFGE. Alfalfa sprouts were the only exposure associated with E. coli O157:H7 infection in both Michigan and Virginia. Seeds used for sprouting were traced back to one common lot harvested in Idaho. New subtyping tools such as PFGE used in this investigation are essential to link isolated infections to a single outbreak.     

Ongoing multistate outbreak of Escherichia coli serotype O157:H7 infections associated with consumption of fresh spinach--United States, September 2006

On September 13, 2006, CDC officials were alerted by epidemiologists in Wisconsin and Oregon that fresh spinach was the suspected source of small clusters of Escherichia coli serotype O157:H7 infections in those states. On the same day, New Mexico epidemiologists contacted Wisconsin and Oregon epidemiologists about a cluster of E. coli O157:H7 infections in New Mexico associated with fresh spinach consumption. Wisconsin public health officials had first reported a cluster of E. coli O157:H7 infections to CDC on September 8. On September 12, CDC PulseNet had confirmed that the E. coli O157:H7 strains from infected patients in Wisconsin had matching pulsed-field gel electrophoresis (PFGE) patterns and identified the same pattern in patient isolates from other states. This report describes the joint investigation and outbreak-control measures undertaken by state public health officials, CDC, and the Food and Drug Administration (FDA). This investigation and additional case finding are ongoing.     

Laboratory-confirmed non-O157 Shiga toxin-producing Escherichia coli--Connecticut, 2000-2005

Shiga toxin-producing Escherichia coli (STEC) infection causes diarrhea that is often bloody and can result in potentially life-threatening hemolytic uremic syndrome (HUS). Escherichia coli O157:H7 is the most common cause of STEC infection in the United States, producing 73,000 illnesses annually, according to the last estimate in 1999. Unlike O157, however, little is known about the incidence of non-O157 strains. Because STEC other than O157 are not commonly identified, the incidence, trends, and epidemiology of non-O157 STEC are not well understood. To assess trends in Shiga toxin enzyme immunoassay (Stx EIA) testing by local clinical laboratories, the Connecticut Department of Public Health (CTDPH) analyzed results of confirmatory testing conducted in the state laboratory during 2000--2005. The findings indicated that a total of 403 STEC infections were reported by clinical laboratories in Connecticut, including 207 identified as STEC by Stx EIA testing alone, and that the use of Stx EIA increased from 2000 to 2005. Use of Stx EIA without prompt culture confirmation can delay or prevent serotyping and subtyping of isolates and detection of both O157 and non-O157 STEC outbreaks. Public health authorities in all states should ensure that clinical laboratories forward Stx EIA-positive specimens to the state laboratory for isolation and identification of STEC, as recommended by the Association of Public Health Laboratories and CDC.     

蚌埠市2000~2005年肠出血性大肠杆菌O_(157):H_7调查研究

目的了解蚌埠市腹泻病人、动物宿主携带肠出血性大肠杆菌O157:H7(EHECO157:H7)情况,为政府决策提供依据。方法采集我市市区和怀远县部分乡镇的现症腹泻病人和动物宿主(牛、羊、猪等)的粪便标本,用免疫磁珠富集法进行EHECO157:H7检测,血清凝集和生化试验对菌株进行鉴定。结果5年间共采集各种标本2955份,检出10株EHECO157:H7,检出率为0.34%。结论蚌埠市部分腹泻病人和动物宿主中存在着EHECO157:H7感染,应进一步加强监测工作。