A university outbreak of Escherichia coli O157:H7 infections associated with roast beef and an unusually benign clinical course

Inhibition of the lethality of Shiga-like toxin-1 by functional gold nanoparticles

Escherichia coli O157:H7 is a pathogen, which can generate Shiga-like toxins (SLTs) and cause hemolytic-uremic syndrome. Foodborne illness outbreaks caused by E. coli O157:H7 have become a global issue. Since SLTs are quite toxic, effective medicines that can reduce the damage caused by SLTs should be explored. SLTs consist of a single A and five B subunits, which can inhibit ribosome activity for protein synthesis and bind with the cell membrane of host cells, respectively. Pigeon ovalbumin (POA), i.e. a glycoprotein, is abundant in pigeon egg white (PEW) proteins. The structure of POA contains Gal-α(1→4)-Gal-β(1→4)-GlcNAc ligands, which have binding affinity toward the B subunit in SLT type-1 (SLT-1B). POA immobilized gold nanoparticles (POA-Au NPs) can be generated by reacting PEW proteins with aqueous tetrachloroauric acid in one-pot. The generated POA-Au NPs have been demonstrated to have selective trapping-capacity toward SLT-1B previously. Herein, we explore that POA-Au NPs can be used as protective agents to neutralize the toxicity of SLT-1 in SLT-1-infected model cells. The results show that the cells can be completely rescued when a sufficient amount of POA-Au NPs is used to treat the SLT-1-infected cells within 1 h.

Shiga Toxin (Verotoxin)-producing Escherichia coli and Foodborne Disease: A Review

Shiga toxin (verotoxin)-producing Escherichia coli (STEC) is an important cause of foodborne disease. Since outcomes of the infections with STEC have a broad range of manifestation from asymptomatic infection or mild intestinal discomfort, to bloody diarrhea, hemolytic uremic syndrome (HUS), end-stage renal disease (ESRD), and death, the disease is a serious burden in public health and classified as a notifiable infectious disease in many countries. Cattle and other ruminants are considered to be the major reservoirs of STEC though isolation of STEC from other animals have been reported. Hence, the source of contamination extends to a wide range of foods, not only beef products but also fresh produce, water, and environment contaminated by excretes from the animals, mainly cattle. A low- infectious dose of STEC makes the disease relatively contagious, and causes outbreaks with unknown contamination sources and, therefore, as a preventive measure against STEC infection, it is important to obtain characteristics of prevailing STEC isolates in the region through robust surveillance. Analysis of the isolates by pulsed-field gel electrophoresis (PFGE) and multiple-locus variable-number tandem repeat analysis (MLVA) could help finding unrecognized foodborne outbreaks due to consumption of respective contaminated sources. However, though the results of molecular analysis of the isolates could indicate linkage of sporadic cases of STEC infection, it is hardly concluded that the cases are related via contaminated food source if it were not for epidemiological information. Therefore, it is essential to combine the results of strain analysis and epidemiological investigation rapidly to detect rapidly foodborne outbreaks caused by bacteria. This article reviews STEC infection as foodborne disease and further discusses key characteristics of STEC including pathogenesis, clinical manifestation, prevention and control of STEC infection. We also present the recent situation of the disease in Japan based on the surveillance of STEC infection.

Routes of Transmission in the Food Chain

More than 250 different foodborne diseases have been described to date, annually affecting about one-third of the world's population. The incidence of foodborne diseases has been underreported and underestimated, and the asymptomatic presentation of some of the illnesses, worldwide heterogeneities in reporting, and the alternative transmission routes of certain pathogens are among the factors that contribute to this. Globalization, centralization of the food supply, transportation of food products progressively farther from their places of origin, and the multitude of steps where contamination may occur have made it increasingly challenging to investigate foodborne and waterborne outbreaks. Certain foodborne pathogens may be transmitted directly from animals to humans, while others are transmitted through vectors, such as insects, or through food handlers, contaminated food products or food-processing surfaces, or transfer from sponges, cloths, or utensils. Additionally, the airborne route may contribute to the transmission of certain foodborne pathogens. Complicating epidemiological investigations, multiple transmission routes have been described for some foodborne pathogens. Two types of transmission barriers, primary and secondary, have been described for foodborne pathogens, each of them providing opportunities for preventing and controlling outbreaks. Primary barriers, the most effective sites of prophylactic intervention, prevent pathogen entry into the environment, while secondary barriers prevent the multiplication and dissemination of pathogens that have already entered the environment. Understanding pathogen dynamics, monitoring transmission, and implementing preventive measures are complicated by the phenomenon of superspreading, which refers to the concept that, at the level of populations, a minority of hosts is responsible for the majority of transmission events.

Magnetic Nanoparticle-Based Platform for Characterization of Shiga-like Toxin 1 from Complex Samples

Foodborne illness outbreaks resulting from contamination of Escherichia coli O157:H7 remain a serious concern in food safety. E. coli O157:H7 can cause bloody diarrhea, hemolytic uremic syndrome, or even death. The pathogenicity of E. coli O157:H7 is mainly caused by the expression of Shiga-like toxins (SLTs), i.e., SLT-1 and SLT-2. SLTs are pentamers composed of a single A and five B subunits. In this study, we propose a magnetic nanoparticle (MNP)-based platform to rapidly identify SLT-1 from the complex cell lysate of E. coli O157:H7. The core of the MNPs is made of iron oxide, whereas the surface of the core is coated with a thin layer of alumina (Fe3O4@Al2O3 MNPs). The Fe3O4@Al2O3 MNPs are functionalized with pigeon ovalbumin (POA), which contains Gal-α(1→4)-Gal-β(1→4)-GlcNAc termini that can bind SLT-1B selectively. Furthermore, POA is a phosphate protein. Thus, it can be easily immobilized on the surface of the Fe3O4@Al2O3 MNPs through aluminum phosphate chelation under microwave heating within 1.5 min. The generated POA-Fe3O4@Al2O3 MNPs are capable of effectively enriching SLT-1B from complex cell lysates simply by pipetting 20 μL of the sample in and out of the tip in a vial for ∼1 min. To release SLT-1 from the MNPs, Gal-α(1→4)-Gal disaccharides were used for displacement. The released target species are sufficient to be identified by matrix-assisted laser desorption/ionization mass spectrometry. Although the sample volume used in this approach is small (20 μL) and the enrichment time is short (1 min), the selectivity of this approach toward SLT-1B is quite good. We have demonstrated the effectiveness of this approach for rapid determination of the presence of SLT-1 from complex cell lysates and ham/juice samples based on the detection of SLT-1B.

Prevalence and concentration of Escherichia coli O157 in different seasons and cattle types processed in North America: A systematic review and meta-analysis of published research

Systematic review (SR) and meta-analyses (MA) methodologies were used to identify, critically evaluate and synthesize prevalence and concentration estimates for Escherichia coli O157 contamination along the beef production chain, and to illustrate differences based on cattle types and seasonality in North America from the scientific peer-reviewed literature. Four electronic databases were searched to identify relevant articles. Two independent reviewers performed all SR steps. Random effects MA models were used to estimate the pooled prevalence and concentration of E. coli O157 in feces, hides and carcasses of cattle processed in North America, including their seasonal estimates. The potential sources of between studies heterogeneity were identified using meta-regression and sub-group analysis. Results indicated differences in the fecal prevalence of E. coli O157 among cattle types: 10.68% (95% CI: 9.17-12.28%) in fed beef, 4.65% (95% CI: 3.37-6.10%) in adult beef, and 1.79% (95% CI: 1.20-2.48%) in adult dairy. Fed beef fecal prevalence was 10.65% (95% CI: 8.93-12.49%) during summer and 9.17% (95% CI: 5.24-13.98%) during the winter months. For adult beef, the fecal prevalence was 7.86% (95% CI: 5.43-10.66%) during summer, and 4.21% (95% CI: 1.95-7.13%) during winter. Among adult dairy, the fecal prevalence was 2.27% (95% CI: 1.5-3.18%) during summer, and 0.36% (95% CI: 0.09-0.74%) during winter. There was a significantly higher percentage of hides with E. coli O157 concentration ≥ 40 CFU/100 cm(2) on hides of fed beef sampled at the processing plant (23.81%; 95% CI: 14.79-34.15%) compared to those sampled at the feedlot (1.74%; 95% CI: 0.53-3.44%). Prevalence of E. coli O157 on carcass surfaces differed by season only at the post-evisceration stage, but decreased considerably through the subsequent processing stages. Country, study setting, detection method, hide swab area, and study design were identified as significant sources of heterogeneity among studies reporting prevalence of E. coli O157 along the beef production chain. The pooled prevalence and concentration estimates from this study provide a sound and reliable microbiological basis for risk assessment modeling of E. coli O157 and other pathogens in the food chain.

Management of hemolytic-uremic syndrome in children

Acute renal failure associated with a fulminant, life-threatening systemic disease is rare in previously healthy young children; however, when it occurs, the most common cause is hemolytic-uremic syndrome (HUS). In most cases (90%), this abrupt and devastating illness is a result of ingestion of food or drink contaminated with pathogens that produce very potent toxins. Currently, there are no proven treatment options that can directly inactivate the toxin or effectively interfere with the cascade of destructive events triggered by the toxin once it gains access to the bloodstream and binds its receptor. However, HUS is self-limited, and effective supportive management during the acute phase is proven to be a life saver for children affected by HUS. A minority of childhood HUS cases, approximately 5%, are caused by various genetic mutations causing uncontrolled activation of the complement system. These children, who used to have a poor prognosis leading to end-stage renal disease, now have access to exciting new treatment options that can preserve kidney function and avoid disease recurrences. This review provides a summary of the current knowledge on the epidemiology, pathophysiology, and clinical presentation of childhood HUS, focusing on a practical approach to best management measures.

Treatment of Shiga toxin-producing Escherichia coli infections

The management of Shiga toxin-producing Escherichia coli (STEC) infections is reviewed. Certain management practices optimize the likelihood of good outcomes, such as avoidance of antibiotics during the pre-hemolytic uremic syndrome phase, admission to hospital, and vigorous intravenous volume expansion using isotonic fluids. The successful management of STEC infections is based on recognition that a patient might have an STEC infection, and appropriate use of the microbiology laboratory. The timeliness of STEC identification cannot be overemphasized, because it avoids therapies prompted by inappropriate additional testing and directs the clinician to focus on effective management strategies. The opportunities during STEC infections to avert the worst outcomes are brief, and this article emphasizes practical matters relevant to making a diagnosis, anticipating the trajectory of illness, and optimizing care.

Association of nucleotide polymorphisms within the O-antigen gene cluster of Escherichia coli O26, O45, O103, O111, O121, and O145 with serogroups and genetic subtypes

Shiga toxin-producing Escherichia coli (STEC) strains are important food-borne pathogens capable of causing hemolytic-uremic syndrome. STEC O157:H7 strains cause the majority of severe disease in the United States; however, there is a growing concern for the amount and severity of illness attributable to non-O157 STEC. Recently, the Food Safety and Inspection Service (FSIS) published the intent to regulate the presence of STEC belonging to serogroups O26, O45, O103, O111, O121, and O145 in nonintact beef products. To ensure the effective control of these bacteria, sensitive and specific tests for their detection will be needed. In this study, we identified single nucleotide polymorphisms (SNPs) in the O-antigen gene cluster that could be used to detect STEC strains of the above-described serogroups. Using comparative DNA sequence analysis, we identified 22 potentially informative SNPs among 164 STEC and non-STEC strains of the above-described serogroups and designed matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) assays to test the STEC allele frequencies in an independent panel of bacterial strains. We found at least one SNP that was specific to each serogroup and also differentiated between STEC and non-STEC strains. Differences in the DNA sequence of the O-antigen gene cluster corresponded well with differences in the virulence gene profiles and provided evidence of different lineages for STEC and non-STEC strains. The SNPs discovered in this study can be used to develop tests that will not only accurately identify O26, O45, O103, O111, O121, and O145 strains but also predict whether strains detected in the above-described serogroups contain Shiga toxin-encoding genes.

Factors associated with sporadic verotoxigenic Escherichia coli infection in children with diarrhea from the Central Eastern Area of Argentina

Verotoxigenic Escherichia coli (VTEC) are one of the most important emerging foodborne pathogens and the principal cause of hemolytic uremic syndrome (HUS). This entity has been recognized worldwide as a priority issue in the field of zoonoses and public health, and Argentina is the country with the highest incidence of HUS in children less than 5 years of age.The lack of specific treatment, combined with the high morbidity rate of VTEC infection, makes prevention the main tool for reducing the incidence of HUS. The current work aimed at assessing the factors associated with sporadic VTEC infection in children with acute diarrhea from the Central Eastern area of Argentina where the incidence rate of HUS in children under 5 is the highest worldwide. A univariate analysis was performed to identify potential factors associated with VTEC infection by calculating odds ratios (OR) with 95% confidence intervals (CI). Then, a multivariate logistic regression model was performed. Interaction and association between significant factors were checked. "Recent consumption of food prepared outside home" (OR: 2.4, 95% CI 1.05-5.7) and "recent vegetables consumption" (OR=0.4; 0.2-0.8) were identified as independent factors associated with VTEC infection. We believe that the data obtained from this study further the current knowledge about the epidemiology of VTEC infection in Argentina and could be considered when planning strategies for the prevention of the disease.

Escherichia coli O157:H7: recent advances in research on occurrence, transmission, and control in cattle and the production environment

Escherichia coli O157:H7 is a zoonotic pathogen that is an important cause of human foodborne and waterborne disease, with a spectrum of illnesses ranging from asymptomatic carriage and diarrhea to the sometimes fatal hemolytic uremic syndrome. Outbreaks of E. coli O157:H7 disease are often associated with undercooked beef, but there are other sources of transmission, including water, produce, and animal contact, which can often be linked directly or indirectly to cattle. Thus, preharvest control of this pathogen in cattle production should have a large impact on reducing the risk of human foodborne illness. In this review, we will summarize preharvest research on E. coli O157:H7 in cattle and the production environment, focusing on factors that may influence the transmission, prevalence, and levels of this pathogen, such as season, diet, high-level shedders, and animal stress. In addition, we will discuss recent research on the reduction of this pathogen in cattle production, including vaccination, probiotics, bacteriophage, and manure treatments.

Primary and secondary cases in Escherichia coli O157 outbreaks: a statistical analysis

Background

Within outbreaks of Escherichia coli O157 (E. coli O157), at least 10–15% of cases are thought to have been acquired by secondary transmission. However, there has been little systematic quantification or characterisation of secondary outbreak cases worldwide. The aim of this study was to characterise secondary outbreak cases, estimate the overall proportion of outbreak cases that were the result of secondary transmission and to analyse the relationships between primary and secondary outbreak cases by mode of transmission, country and median age.

Methods

Published data was obtained from 90 confirmed Escherichia coli O157 outbreaks in Great Britain, Ireland, Scandinavia, Canada, the United States and Japan, and the outbreaks were described in terms of modes of primary and secondary transmission, country, case numbers and median case age. Outbreaks were tested for statistically significant differences in the number of ill, confirmed, primary and secondary cases (analysis of variance and Kruskal-Wallis) and in the rate of secondary cases between these variables (Generalised Linear Models).

Results

The outbreaks had a median of 13.5 confirmed cases, and mean proportion of 0.195 secondary cases. There were statistically significant differences in the numbers of ill, confirmed, primary and secondary cases between modes of primary transmission (p < 0.021), and in primary and secondary cases between median age categories (p < 0.039) and modes of secondary transmission (p < 0.001).

Secondary case rates differed statistically significantly between modes of secondary and primary transmission and median age categories (all p < 0.001), but not between countries (p = 0.23). Statistically significantly higher rates of secondary transmission were found in outbreaks with a median age <6 years and those with secondary transmission via person to person spread in nurseries. No statistically significant interactions were found between country, mode of transmission and age category.

Conclusion

Our analyses indicated that ~20% of E. coli O157 outbreak cases were the result of secondary spread, and that this spread is significantly influenced by age and modes of primary and secondary transmission, but not country. In particular, the results provide further data emphasising the importance of simple but effective preventive strategies, such as handwashing, that can reduce the risk of secondary spread, particularly amongst young children in nurseries.

A national outbreak of verotoxin-producing Escherichia coli O157 associated with consumption of lemon-and-coriander chicken wraps from a supermarket chain

A national outbreak of verotoxin-producing Escherichia coli O157 infection affected five English regions and Wales. Twelve cases were associated with lemon-and-coriander chicken wrap from a single supermarket chain consumed over a 5-day period. An outbreak investigation aimed to identify the source of infection. Descriptive epidemiology and phenotypic and genotypic tests on human isolates indicated a point-source outbreak; a case-control study showed a very strong association between consumption of lemon-and-coriander chicken wrap from the single supermarket chain and being a case (OR 46.40, 95% CI 5.39-infinity, P=0.0002). Testing of raw ingredients, products and faecal samples from staff in the food production unit did not yield any positive results. The outbreak was probably caused by one contaminated batch of an ingredient in the chicken wrap. Even when current best practice is in place, ready-to-eat foods can still be a risk for widespread infection.

Antimicrobial efficacy of eugenol microemulsions in milk against Listeria monocytogenes and Escherichia coli O157:H7

The antimicrobial activity of eugenol microemulsions (eugenol encapsulated in surfactant micelles) in ultrahigh-temperature pasteurized milk containing different percentages of milk fat (0, 2, and 4%) was investigated. Antimicrobial microemulsions were prepared from a 5% (wt) aqueous surfactant solution (Surfynol 485W) with 0.5% (wt) eugenol. Two strains each of Listeria monocytogenes and Escherichia coli O157:H7 previously shown to be the least and most resistant to the microemulsion in microbiological media were used to inoculate sterile milk (10(4) CFU/ml). Samples were withdrawn and plated at 0, 1, 3, 6, 12, and 24 h for enumeration. Microemulsions completely prevented growth of L. monocytogenes for up to 48 h in skim milk and reduced both strains of E. coli O157:H7 to less than detectable levels in less than 1 h. Similarly, in 2% fat milk, eugenol-Surfynol combinations reduced both strains of E. coli O157:H7 to less than detectable levels in less than 1 h but only increased the lag phase of both strains of L. monocytogenes. In full-fat milk (4% fat), microemulsions inhibited growth of the least resistant strains of L. monocytogenes and E. coli but were ineffective against the two resistant strains. Unencapsulated eugenol was slightly more or as inhibitory as microemulsions against target pathogens. Results were attributed to diffusional mass transport of antimicrobials from microemulsions to the macroemulsion (milk). Results suggest that food composition, especially fat level, may affect the efficiency of targeting of foodborne pathogens with surfactant-encapsulated antimicrobials.

Differences in virulence among Escherichia coli O157:H7 strains isolated from humans during disease outbreaks and from healthy cattle

Escherichia coli O157:H7 causes life-threatening outbreaks of diarrhea, hemorrhagic colitis, and hemolytic-uremic syndrome in humans and significant economic loss in agriculture and could be a potential agent of bioterrorism. Although the prevalence of E. coli O157:H7 in cattle and other species with which humans have frequent contact is high, human infections are relatively uncommon, despite a low infectious dose. A plausible explanation for the low disease incidence is the possibility that not all strains are virulent in humans. If there are substantial differences in virulence among strains in nature, then human disease may select for high virulence. We used a gnotobiotic piglet model to investigate the virulence of isolates from healthy cattle and from humans in disease outbreaks and to determine the correlation between production of Shiga toxin 1 (Stx1) and Stx2 and virulence. Overall, E. coli O157:H7 strains isolated from healthy cattle were less virulent in gnotobiotic piglets than strains isolated from humans during disease outbreaks. The amount of Stx2 produced by E. coli O157:H7 strains correlated with strain virulence as measured by a reduction in piglet survival and signs of central nervous system disease due to brain infarction. The amount of Stx1 produced in culture was not correlated with the length of time of piglet survival or with signs of central nervous system disease. We suggest that disease outbreaks select for producers of high levels of Stx2 among E. coli O157:H7 strains shed by animals and further suggest that Stx1 expression is unlikely to be significant in human outbreaks.

Effectiveness of simulated interventions in reducing the estimated prevalence ofE. coliO157:H7 in lactating cows in dairy herds

A transmission model developed to investigate the dynamics of Escherichia coli O157:H7 bacteria in a typical Dutch dairy herd was used to assess the effectiveness of vaccination, diet modification, probiotics (colicin) and hygienic measures as to water troughs and bedding, when they are applied single or in combination, in reducing the prevalence of infected animals. The aim was to rank interventions based on their effectiveness in reducing the baseline prevalence of infected animals in the lactating group. The baseline prevalence of the lactating group and the within-herd prevalence were estimated by the model to be 5.02% and 13.96% respectively. The results show that all four interventions, if applied to all four animal groups or only to young stock, are the most effective and will reduce the baseline prevalence by 84% to 99%. In general, combinations of hygiene (applied in all groups) and one other intervention had the highest effectiveness in reducing prevalence in the lactating group. Vaccination and diet modification show a slightly higher effectiveness than colicin and hygiene.

Prevalence and pathogenicity of Shiga toxin-producing Escherichia coli in beef cattle and their products1,2

During the past 23 yr, a large number of human illness outbreaks have been traced worldwide to consumption of undercooked ground beef and other beef products contaminated with Shiga toxin-producing Escherichia coli (STEC). Although several routes exist for human infection with STEC, beef remains a main source. Thus, beef cattle are considered reservoirs of O157 and nonO157 STEC. Because of the global nature of the food supply, safety concerns with beef will continue, and the challenges facing the beef industry will increase at the production and processing levels. To be prepared to address these concerns and challenges, it is critical to assess the beef cattle role in human infection with STEC. Because most STEC outbreaks in the United States were traced to beef containing E. coli O157:H7, the epidemiological studies have focused on the prevalence of this serotype in beef and beef cattle. Worldwide, however, additional STEC serotypes (e.g., members of the O26, O91, O103, O111, O118, O145, and O166 serogroups) have been isolated from beef and caused human illnesses ranging from bloody diarrhea and hemorrhagic colitis to the life-threatening hemolytic uremic syndrome (HUS). To provide a global assessment of the STEC problem, published reports on beef and beef cattle in the past 3 decades were evaluated. The prevalence rates of E. coli O157 ranged from 0.1 to 54.2% in ground beef, from 0.1 to 4.4% in sausage, from 1.1 to 36.0% in various retail cuts, and from 0.01 to 43.4% in whole carcasses. The corresponding prevalence rates of nonO157 STEC were 2.4 to 30.0%, 17.0 to 49.2%, 11.4 to 49.6%, and 1.7 to 58.0%, respectively. Of the 162 STEC serotypes isolated from beef products, 43 were detected in HUS patients and 36 are known to cause other human illnesses. With regard to beef cattle, the prevalence rates of E. coli O157 ranged from 0.3 to 19.7% in feedlots and from 0.7 to 27.3% on pasture. The corresponding prevalence rates of nonO157 STEC were 4.6 to 55.9% and 4.7 to 44.8%, respectively. Of the 373 STEC serotypes isolated from cattle feces or hides, 65 were detected in HUS patients and 62 are known to cause other human illnesses. The results indicated the prevalence of a large number of pathogenic STEC in beef and beef cattle at high rates and emphasized the critical need for control measures to assure beef safety.

Prevalence of Shiga toxin-producing Escherichia coli in beef cattle

A large number of Shiga toxin-producing Escherichia coli (STEC) strains have caused major outbreaks and sporadic cases of human illnesses, including mild diarrhea, bloody diarrhea, hemorrhagic colitis, and the life-threatening hemolytic uremic syndrome. These illnesses have been traced to both O157 and non-O157 STEC. In a large number of STEC-associated outbreaks, the infections were attributed to consumption of ground beef or other beef products contaminated with cattle feces. Thus, beef cattle are considered reservoirs of STEC and can pose significant health risks to humans. The global nature of the human food supply suggests that safety concerns with beef will continue and the challenges facing the beef industry will increase at the production and processing levels. To be prepared to address these concerns and challenges, it is critical to assess the role of beef cattle in human STEC infections. In this review, published reports on STEC in beef cattle were evaluated to achieve the following specific objectives: (i) assess the prevalence of STEC in beef cattle, and (ii) determine the potential health risks of STEC strains from beef cattle. The latter objective is critically important because many beef STEC isolates are highly virulent. Global testing of beef cattle feces revealed wide ranges of prevalence rates for O157 STEC (i.e., 0.2 to 27.8%) and non-O157 STEC (i.e., 2.1 to 70.1%). Of the 261 STEC serotypes found in beef cattle, 44 cause hemolytic uremic syndrome and 37 cause other illnesses.

Outbreak of Escherichia coli O157:H7 infections associated with nonintact blade-tenderized frozen steaks sold by door-to-door vendors

Steaks have not been recognized as an important vehicle of Escherichia coli O157:H7 infection. During 11 to 27 June 2003, the Minnesota Department of Health (MDH) identified four O157 infection cases with the same pulsed-field gel electrophoresis (PFGE) subtype. All four case patients consumed brand A vacuum packed frozen steaks sold by door-to-door vendors. The steaks were blade tenderized and injected with marinade (i.e., nonintact). Information from single case patients in Michigan and Kansas identified through PulseNet confirmed the outbreak. The MDH issued a press release on 27 June to warn consumers, prompting a nationwide recall of 739,000 lb (335,506 kg) of frozen beef products. The outbreak resulted in six culture-confirmed cases (including one with hemolytic uremic syndrome) and two probable cases in Minnesota and single confirmed cases in four other states. The outbreak PFGE subtype of O157 was isolated from unopened brand A bacon-wrapped fillets from five affected Minnesota households. A fillet from one affected household was partially cooked in the laboratory, and the same O157 subtype was isolated from the uncooked interior. The tenderizing and injection processes likely transferred O157 from the surface to the interior of the steaks. These processing methods create new challenges for prevention of O157 infection. Food regulatory officials should reevaluate safety issues presented by nonintact steak products, such as microbiologic hazards of processing methods, possible labeling to distinguish intact from nonintact steaks, and education of the public and commercial food establishments on the increased risk associated with undercooked nonintact steaks. Information on single cases of O157 infection in individual states identified through PulseNet can be critical in solving multistate outbreaks in a timely manner.

Shiga-toxin-producing Escherichia coli and haemolytic uraemic syndrome

Most cases of diarrhoea-associated haemolytic uraemic syndrome (HUS) are caused by Shiga-toxin-producing bacteria; the pathophysiology differs from that of thrombotic thrombocytopenic purpura. Among Shiga-toxin-producing Escherichia coli (STEC), O157:H7 has the strongest association worldwide with HUS. Many different vehicles, in addition to the commonly suspected ground (minced) beef, can transmit this pathogen to people. Antibiotics, antimotility agents, narcotics, and non-steroidal anti-inflammatory drugs should not be given to acutely infected patients, and we advise hospital admission and administration of intravenous fluids. Management of HUS remains supportive; there are no specific therapies to ameliorate the course. The vascular injury leading to HUS is likely to be well under way by the time infected patients seek medical attention for diarrhoea. The best way to prevent HUS is to prevent primary infection with Shiga-toxin-producing bacteria.

Influence of apple cultivars on inactivation of different strains of Escherichia coli O157:H7 in apple cider by UV irradiation

This study examined the effect of different apple cultivars upon the UV inactivation of Escherichia coli O157:H7 strains within unfiltered apple cider. Apple cider was prepared from eight different apple cultivars, inoculated with approximately 10(6) to 10(7) CFU of three strains of E. coli O157:H7 per ml (933, ATCC 43889, and ATCC 43895), and exposed to 14 mJ of UV irradiation per cm(2). Bacterial populations for treated and untreated samples were then enumerated by using nonselective media. E. coli O157:H7 ATCC 43889 showed the most sensitivity to this disinfection process with an average 6.63-log reduction compared to an average log reduction of 5.93 for both strains 933 and ATCC 43895. The highest log reduction seen, 7.19, occurred for strain ATCC 43889 in Rome cider. The same cider produced the lowest log reductions: 5.33 and 5.25 for strains 933 and ATCC 43895, respectively. Among the apple cultivars, an average log reduction range of 5.78 (Red Delicious) to 6.74 (Empire) was observed, with two statistically significant (alpha < or = 0.05) log reduction groups represented. Within the paired cultivar-strain analysis, five of eight ciders showed statistically significant (alpha < or = 0.05) differences in at least two of the E. coli strains used. Comparison of log reductions among the E. coli strains to the cider parameters of (o)Brix, pH, and malic acid content failed to show any statistically significant relationship (R(2) > or = 0.95). However, the results of this study indicate that regardless of the apple cultivar used, a minimum 5-log reduction is achieved for all of the strains of E. coli O157:H7 tested.

Effective medicinal plants against enterohaemorrhagic Escherichia coli O157:H7

The stimulating effect of subinhibitory concentrations of antibiotics on the production of verocytotoxin (VT) by enterohaemorrhagic Escherichia coli (EHEC) O157:H7 has been claimed. The purpose of this study was to find an alternative, but bioactive medicine for the treatment of this organism. Fifty-eight preparations of aqueous and ethanolic extracts of 38 medicinal plant species commonly used in Thailand to cure gastrointestinal infections were tested for their antibacterial activity against different strains of Escherichia coli, including 6 strains of Escherichia coli O157:H7, Escherichia coli O26:H11, Escherichia coli O111:NM, Escherichia coli O22; 5 strains of Escherichia coli isolated from bovine; and Escherichia coli ATCC 25922. Inhibition of growth was primarily tested by the paper disc agar diffusion method. Among the medicinal plants tested, only 8 species (21.05%) exhibited antimicrobial activity against Escherichia coli O157:H7. Acacia catechu, Holarrhena antidysenterica, Peltophorum pterocarpum, Psidium guajava, Punica granatum, Quercus infectoria, Uncaria gambir, and Walsura robusta demonstrated antibacterial activity with inhibition zones ranging from 7 to 17 mm. The greatest inhibition zone against Escherichia coli O157:H7 (RIMD 05091083) was produced from the ethanolic extract of Quercus infectoria. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined by the agar microdilution method and agar dilution method in petri dishes with millipore filter. Both aqueous and ethanolic extracts of Quercus infectoria and aqueous extract of Punica granatum were highly effective against Escherichia coli O157:H7 with the best MIC and MBC values of 0.09, 0.78, and 0.19, 0.39 mg/ml, respectively. These plant species may provide alternative but bioactive medicines for the treatment of Escherichia coli O157:H7 infection.

Outbreak of Shiga Toxin–ProducingEscherichia coliO111:H8 Infections among Attendees of a High School Cheerleading Camp

Few US clinical laboratories screen stool specimens for Shiga toxin-producing Escherichia coli (STEC) other than E. coli O157. An outbreak of STEC O111:H8 infections indistinguishable from E. coli O157:H7 at a youth camp highlights the need to improve non-O157 STEC surveillance. Interviews of 521 (80%) of 650 attendees revealed 55 (11%) were ill; 2 developed hemolytic-uremic syndrome. Illness was associated with consuming salad during the camp's first lunch meal (hazard ratio [HR], 4.68; P<.01), consuming ice provided in barrels on the camp's final day (HR, 3.41; P<.01), eating cob corn (HR, 3.22; P<.01), and eating a dinner roll (HR, 2.82; P<.01). Cultures of 2 of 11 stools yielded E. coli O111:H8. Results of serologic testing and additional stool cultures demonstrated no evidence of infection with other bacterial pathogens, including E. coli O157, and supported infection with E. coli O111. Clinical laboratories should routinely screen suspect specimens for non-O157 STEC and should serotype and report Shiga-positive isolates.

Isolation of Escherichia coli O157:H7 from foods in Greece

The presence of Escherichia coli O157:H7 in various foods of animal origin was surveyed in northwestern Greece. Six hundred samples of unpasteurized cows', ewes' and goats' milk, raw minced meat, uncooked frozen beef hamburgers, sandwiches (containing ham or turkey, mixed vegetable salad with mayonnaise and lettuce), fresh traditional Greek pork sausages and swine intestines appropriate for traditional Greek kokoretsi were assayed for E. coli serogroup O157:H7 using the standard cultural method and the immunomagnetic separation technique. The pathogen was detected in 1 out of 100 (1.0%) samples of ewes' milk, 1 out of 75 (1.3%) fresh sausages and 1 out of 50 (2.0%) swine intestines prepared for kokoretsi. The isolated strains were nonsorbitol fermenters, MUG-negative, O157 agglutinating, verotoxin-producing and carried both VT1 and VT2 genes. The three isolated strains were tested for antibiotic resistance and were found to be susceptible to eight antimicrobial agents (ampicillin, chloramphenicol, kanamycin, nalidixic acid, norfloxacin, streptomycin, sulfamethoxazole-trimethoprim and tetracycline).

Genotypic analyses of Escherichia coli O157:H7 and O157 nonmotile isolates recovered from beef cattle and carcasses at processing plants in the Midwestern states of the United States

Escherichia coli O157:H7 and O157 nonmotile isolates (E. coli O157) previously were recovered from feces, hides, and carcasses at four large Midwestern beef processing plants (R. O. Elder, J. E. Keen, G. R. Siragusa, G. A. Barkocy-Gallagher, M. Koohmaraie, and W. W. Laegreid, Proc. Natl. Acad. Sci. USA 97:2999-3003, 2000). The study implied relationships between cattle infection and carcass contamination within single-source lots as well as between preevisceration and postprocessing carcass contamination, based on prevalence. These relationships now have been verified based on identification of isolates by genomic fingerprinting. E. coli O157 isolates from all positive samples were analyzed by pulsed-field gel electrophoresis of genomic DNA after digestion with XbaI. Seventy-seven individual subtypes (fingerprint patterns) grouping into 47 types were discerned among 343 isolates. Comparison of the fingerprint patterns revealed three clusters of isolates, two of which were closely related to each other. Remarkably, isolates carrying both Shiga toxin genes and nonmotile isolates largely fell into specific clusters. Within lots analyzed, 68.2% of the postharvest (carcass) isolates matched preharvest (animal) isolates. For individual carcasses, 65.3 and 66.7% of the isolates recovered postevisceration and in the cooler, respectively, matched those recovered preevisceration. Multiple isolates were analyzed from some carcass samples and were found to include strains with different genotypes. This study suggests that most E. coli O157 carcass contamination originates from animals within the same lot and not from cross-contamination between lots. In addition, the data demonstrate that most carcass contamination occurs very early during processing.

Escherichia coli O157:H7

E. coli O157:H7 can cause potentially lethal illness in hosts of all ages. These patients often are evaluated and treated by gastroenterologists. The treating physician should administer adequate hydration, usually parenterally, and avoid the use of antibiotics and antimotility agents. The physician needs to notify immediately the appropriate public health authorities of the diagnosis and to ensure that the isolate is recovered by the microbiologist and forwarded for molecular linkage analyses.

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.

Macrolides and clindamycin suppress the release of Shiga-like toxins from Escherichia coli O157:H7 in vitro

We investigated the effects of antimicrobial agents fosfomycin (FOS), cefdinir (CDIN), levofloxacin (LEVX), rokitamycin (ROK), roxithromycin (ROX), and clindamycin (CLI) on the release of Shiga-like toxins (SLTs) by enterohaemorrhagic Escherichia coli (EHEC). EHEC was cultured for 14 h in the presence of ROX, ROK or CLI at sub-minimum inhibitory concentrations (subMICs) of 1.56-6.25 mg/l, followed by assay of the level of SLTs in the supernatants using cytotoxicity assay and reversed passive latex agglutination method. Exposure to ROX, ROK or CLI reduced the amount of released SLTs compared with untreated control cultures (P<0.05). These agents however, did not decrease the number of viable EHEC, indicating the importance of bactericidal agents. When the bacteria was exposed to CDIN, FOS or LEVX, the level of SLTs in the culture supernatant increased with the destruction of bacterial cells in the order of CDIN, FOS, LEVX. When 0.5 mg/l of LEVX was added to cultures with or without pretreatment using ROX, ROK, or CLI, the release of SLTs was reduced by this pretreatment (P<0.05). These results may have clinical implications for the treatment of EHEC infection.

Epidemiology and diagnosis of Shiga toxin-producing Escherichia coli infections

Shiga toxin-producing Escherichia coli (STEC) have been identified as a worldwide cause of serious human gastrointestinal disease and the life-threatening hemolytic uremic syndrome. The most common serotype implicated is E. coli O157: H7, but infections involving various non-O157 serotypes have been found with increasing frequency in many countries. Food-borne outbreaks caused by STEC can affect large numbers of people and cause serious morbidity, making the bacteria one of the most important emerging pathogens. Because there is no specific treatment of the disease currently available, there is an urgent need for effective preventive measures based on a detailed understanding of the epidemiology of STEC infections. Such measures will also be dependent on the availability of rapid, sensitive, and simple procedures for the detection of the pathogens both in human samples and in samples of nonhuman origin such as food. This review summarizes the current knowledge on the epidemiology of STEC infection and presents a survey of laboratory methods currently available for diagnosis of STEC. Special attention is given to new diagnostic procedures for the less readily detectable non-O157 STEC strains and to simple procedures, usually based on commercially available kits, that can be used in routine clinical microbiological laboratories.

Factory outbreak of Escherichia coli O157:H7 infection in Japan

To determine the cause of a July 1996 outbreak of Escherichia coli O157:H7 among factory workers in Kyoto, Japan, we conducted cohort and case-control studies. Eating radish sprout salad during lunch at the factory cafeteria had been linked to illness. The sprouts were traced to four growers in Japan; one had been associated with an outbreak of E. coli O157:H7 among 6,000 schoolchildren in Sakai earlier in July.

Escherichia coli O157:H7

Escherichia coli O157 was first identified as a human pathogen in 1982. One of several Shiga toxin-producing serotypes known to cause human illness, the organism probably evolved through horizontal acquisition of genes for Shiga toxins and other virulence factors. E. coli O157 is found regularly in the faeces of healthy cattle, and is transmitted to humans through contaminated food, water, and direct contact with infected people or animals. Human infection is associated with a wide range of clinical illness, including asymptomatic shedding, non-bloody diarrhoea, haemorrhagic colitis, haemolytic uraemic syndrome, and death. Since laboratory practices vary, physicians need to know whether laboratories in their area routinely test for E. coli O157 in stool specimens. Treatment with antimicrobial agents remains controversial: some studies suggest that treatment may precipitate haemolytic uraemic syndrome, and other studies suggest no effect or even a protective effect. Physicians can help to prevent E. coli O157 infections by counselling patients about the hazards of consuming undercooked ground meat or unpasteurised milk products and juices, and about the importance of handwashing to prevent the spread of diarrhoeal illness, and by informing public-health authorities when they see unusual numbers of cases of bloody diarrhoea or haemolytic uraemic syndrome.

Insertion element IS3-based PCR method for subtyping Escherichia coli O157:H7

An Escherichia coli O157:H7 subtyping method based on PCR amplification of variable DNA sequences between the repetitive element IS3 was developed. Template DNA was prepared by boiling cells in Chelex. Two separate IS3 PCR amplifications were performed for each isolate: one with a single primer (primer IS3A) and one with two primers (primers IS3A and IS3B). The IS3 PCR subtyping method was applied to 35 epidemiologically related and unrelated E. coli O157:H7 isolates that had been previously characterized by pulsed-field gel electrophoresis (PFGE). PFGE identified 25 different subtypes (difference of one or more bands). PCR with single primer IS3A and primer pair IS3A-IS3B identified 6 and 14 different subtypes, respectively. By combining the results of the two PCR amplifications, 15 different IS3 PCR subtypes were identified. While not as sensitive as PFGE, IS3 PCR subtyping grouped all outbreak-related isolates. IS3 PCR banding patterns were reproducible between amplifications and between subcultures. IS3 PCR could serve as a simple, rapid screening method for the identification of unrelated E. coli O157:H7 isolates.

Surveillance for Escherichia coli O157:H7 infections in Minnesota by molecular subtyping

BACKGROUND

Escherichia coli O157:H7 is a leading cause of diarrhea and the hemolytic-uremic syndrome. Current public health surveillance for E. coli O157:H7 requires considerable resources; traditional methods lack the sensitivity and specificity to detect outbreaks effectively.

METHODS

During 1994 and 1995, the Minnesota Department of Health requested that all clinical isolates of E. coli O157:H7 be submitted to our laboratory. Isolates were subtyped by pulsed-field gel electrophoresis (PFGE), and patients were interviewed about potential sources of infection.

RESULTS

In 1994 and 1995, 344 cases of E. coli O157:H7 infection were reported to the Minnesota Department of Health; 317 (92 percent) were subtyped by PFGE, and 143 distinct PFGE patterns were identified. Ten outbreaks of E. coli O157:H7 were identified; these accounted for 56 (18 percent) of the 317 subtyped cases. Four outbreaks were detected solely as a result of subtype-specific surveillance. In 11 two-week periods, the number of reported cases of E. coli O157:H7 doubled from the previous two weeks. In eight of these instances, the patterns identified were dissimilar and there were no outbreaks. Two of the remaining three increases resulted from multiple simultaneous outbreaks.

CONCLUSIONS

Subtype-specific surveillance for E. coli O157:H7 can identify outbreaks that are not detected by traditional methods and can ascertain whether sudden increases in reported cases are due to sporadic isolated cases or to one or more outbreaks.