Prevalence Of Shiga Toxin-producing Escherichia Coli Research Articles

Shiga Toxin Producing Escherichia Coli Presence in Environmental Samples Collected from 4 Different Meat Processing Plants in Honduras

ObjectivesTo create a baseline of Shiga toxin producing Escherichia coli (STEC) presence in meat processing facilities in Honduras.Materials and MethodsSwab samples from tables, saws, equipment, knifes, aprons, walls, floors, drains, tubs, baskets, axes, boots, carts, hands, weighs and shelves were sampled in 4 different meat processing plants in Honduras. Plants A and B have an implemented HACCP system, while plants C and D have no food safety system in place. Surfaces were swabbed with pre-hydrated sponges, and all sponge samples were subjected to BAX STEC screening after enrichment. Presumptive positives underwent immunomagnetic separation for the serotype of interest and were plated onto modified Rainbow Agar. Individual colonies were confirmed through slide agglutination. Procedures of R (v3.3.2) were used for statistical analysis.ResultsThere was no significant difference (P = 0.93) in the STEC presence among the 4 plants. The prevalence of STEC in environmental samples in plants A, B, C and D was 7.3% (4/55), 10.0% (4/40), 7.1% (1/14) and 11.1% (3/27), respectively. The use of HACCP as a food safety management system did not influence (P = 0.97) the prevalence of STEC in environmental samples.ConclusionThe USDA-FSIS currently recommends that establishments test food contact surfaces for STEC (or virulence markers), and if the surface is found positive then the product that came in direct contact with those surfaces may be considered adulterated. Hence, it is crucial that meat plants maintain strict sanitation regimes for decontamination of environmental surfaces that may act as reservoirs for STEC. A reassessment of sanitation and HACCP plans in plants A and B is urgent, given that the system is not currently eliminating environmental STEC, while the development and implementation of food safety systems is needed in facilities C and D to protect public health in Honduras.

Faecal carriage of extended-spectrum β-lactamase-producing Enterobacteriaceae and Shiga toxin-producing Escherichia coli in asymptomatic nursery children in Lower Saxony (Germany), 2014.

Children may be at higher risk for carriage of antimicrobial-resistant bacteria because of higher usage of antimicrobials. They also have higher rates of Shiga toxin-producing Escherichia coli (STEC) infections than other population groups. Some infections, particularly in children, are asymptomatic, but still lead to the excretion of large numbers of bacteria and viruses that may cause clinical disease in other individuals. That is one reason why, in Lower Saxony as in other German federal states - asymptomatic carriers of STEC are excluded from nurseries and schools until three consecutive stool samples test negative in order to prevent secondary cases. The prevalence of children who are asymptomatic STEC carriers is unknown. But if it is high, this measure would have substantial socioeconomic effects on families. Infections with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-E) are an increasing problem for public health, especially for hospitals. However, there are no reliable estimates of the prevalence of asymptomatic ESBL-E carriers in Lower Saxony, as there is no mandatory requirement to report these carriers. In order to discuss the exclusion policies for children attending nurseries and ascertain a baseline of ESBL-E carriers, we conducted a cross-sectional study. The aim was to determine the prevalence of ESBL-E and STEC and identify risk factors for carriage in nursery children without diarrhoea (asymptomatic) aged 0-6 years in four selected districts in Northern Germany. During April-September 2014, we collected stool specimens with the support of voluntarily participating nurseries. We tested for STEC by PCR and for ESBL-E on chromogenic agar. Questionnaires answered by parents contained data on eating and drinking habits, outdoor activities, prior antibiotic treatment and animal contact for each participating child. We compared the epidemiological characteristics of ESBL-E carriers vs. non-carriers by using univariable analysis (P value, odds ratio and 95% confidence interval). We could not perform a statistical analysis for STEC carriers due to the low numbers of positive STEC specimens. Of 224 asymptomatic nursery children, we found a prevalence of 2·3% for ESBL-E carriage and 0·5% for STEC carriage. Asymptomatic ESBL-E carriers were more likely to have consumed raw milk, have had contact with pet rodents, or to have taken antibiotics during the preceding 6 months. We also found a high proportion of raw milk consumption (11%). We suggest that the low STEC prevalence in asymptomatic children supports the current practice of excluding STEC carriers from nurseries. The association between ESBL-E carriage and raw milk consumption and contact with pet rodents needs further investigation.

Molecular characterization and antimicrobial resistance of STEC strains isolated from healthy cattle in 2011 and 2013 in Spain.

Prevention of Shiga toxin-producing Escherichia coli (STEC) foodborne outbreaks is hampered by its complex epidemiology. We assessed the distribution of virulence genes (VGs), main serogroups/serotypes for public health [haemolytic uraemic syndrome (HUS)-related], antimicrobial resistance (AMR) profiles and pulsed-field gel electrophoresis (PFGE) patterns in a collection of STEC isolates obtained from cattle hide (n = 149) and faecal (n = 406) samples collected during a national survey conducted in Spain in 2011 and 2013. Isolates were cultured using McConkey and CT-SMAC agar after enrichment, and confirmed as STEC by PCR. STEC prevalence in hides (15·4%) was higher than in faeces (10·7%) and O157:H7 was more frequent in the former (2·7% vs. 0·99%). Non-O157 HUS-related serogroups were present albeit at low frequencies. The non-O157 isolates were more heterogeneous than O157:H7 in their VG patterns, with 25/64 presenting VGs from both STEC and enterotoxigenic pathotypes (hybrid isolates). Of the STEC isolates, 62·5% were resistant at least to one antimicrobial, and no differences in AMR between O157:H7 and non-O157 were detected. All isolates had different profiles by PFGE and did not form a cluster. Overall, our results demonstrated that STEC in the cattle reservoir is still a matter of concern for human health due to the presence of HUS-related serogroups, the occurrence of certain VGs, AMR and the additional risks that hybrid isolates may pose, and thus warrants further investigation.

Factors Associated with Shiga Toxin-Producing Escherichia coli Shedding by Dairy and Beef Cattle.

Shiga toxin-producing Escherichia coli (STEC) is an important foodborne pathogen that can cause hemorrhagic colitis and hemolytic-uremic syndrome. Cattle are the primary reservoir for STEC, and food or water contaminated with cattle feces is the most common source of infections in humans. Consequently, we conducted a cross-sectional study of 1,096 cattle in six dairy herds (n = 718 animals) and five beef herds (n = 378 animals) in the summers of 2011 and 2012 to identify epidemiological factors associated with shedding. Fecal samples were obtained from each animal and cultured for STEC. Multivariate analyses were performed to identify risk factors associated with STEC positivity. The prevalence of STEC was higher in beef cattle (21%) than dairy cattle (13%) (odds ratio [OR], 1.76; 95% confidence interval [CI], 1.25, 2.47), with considerable variation occurring across herds (range, 6% to 54%). Dairy cattle were significantly more likely to shed STEC when the average temperature was >28.9°C 1 to 5 days prior to sampling (OR, 2.5; 95% CI, 1.25, 4.91), during their first lactation (OR, 1.8; 95% CI, 1.1, 2.8), and when they were <30 days in milk (OR, 3.9; 95% CI, 2.1, 7.2). These data suggest that the stress or the negative energy balance associated with lactation may result in increased STEC shedding frequencies in Michigan during the warm summer months. Future prevention strategies aimed at reducing stress during lactation or isolating high-risk animals could be implemented to reduce herd-level shedding levels and avoid transmission of STEC to susceptible animals and people. STEC shedding frequencies vary considerably across cattle herds in Michigan, and the shedding frequency of strains belonging to non-O157 serotypes far exceeds the shedding frequency of O157 strains, which is congruent with human infections in the state. Dairy cattle sampled at higher temperatures, in their first lactation, and early in the milk production stage were significantly more likely to shed STEC, which could be due to stress or a negative energy balance. Future studies should focus on the isolation of high-risk animals to decrease herd shedding levels and the potential for contamination of the food supply.

Presence of pathogenic Escherichia coli is correlated with bacterial community diversity and composition on pre-harvest cattle hides.

BackgroundSince 1982, specific serotypes of Shiga toxin-producing Escherichia coli (STEC) have been recognized as significant foodborne pathogens acquired from contaminated beef and, more recently, other food products. Cattle are the major reservoir hosts of these organisms, and while there have been advancements in food safety practices and industry standards, STEC still remains prevalent within beef cattle operations with cattle hides implicated as major sources of carcass contamination. To investigate whether the composition of hide-specific microbial communities are associated with STEC prevalence, 16S ribosomal RNA (rRNA) bacterial community profiles were obtained from hide and fecal samples collected from a large commercial feedlot over a 3-month period. These community data were examined amidst an extensive collection of prevalence data on a subgroup of STEC that cause illness in humans, referred to as enterohemorrhagic E. coli (EHEC). Fecal 16S rRNA gene OTUs (operational taxonomic units) were subtracted from the OTUs found within each hide 16S rRNA amplicon library to identify hide-specific bacterial populations.ResultsComparative analysis of alpha diversity revealed a significant correlation between low bacterial diversity and samples positive for the presence of E. coli O157:H7 and/or the non-O157 groups: O26, O111, O103, O121, O45, and O145. This trend occurred regardless of diversity metric or fecal OTU presence. The number of EHEC serogroups present in the samples had a compounding effect on the inverse relationship between pathogen presence and bacterial diversity. Beta diversity data showed differences in bacterial community composition between samples containing O157 and non-O157 populations, with certain OTUs demonstrating significant changes in relative abundance.ConclusionsThe cumulative prevalence of the targeted EHEC serogroups was correlated with low bacterial community diversity on pre-harvest cattle hides. Understanding the relationship between indigenous hide bacterial communities and populations may provide strategies to limit EHEC in cattle and provide biomarkers for EHEC risk assessment.Electronic supplementary materialThe online version of this article (doi:10.1186/s40168-016-0155-4) contains supplementary material, which is available to authorized users.

From Farm to Table: Follow-Up of Shiga Toxin-Producing Escherichia coli Throughout the Pork Production Chain in Argentina.

Pigs are important reservoirs of Shiga toxin-producing Escherichia coli (STEC). The entrance of these strains into the food chain implies a risk to consumers because of the severity of hemolytic uremic syndrome. This study reports the prevalence and characterization of STEC throughout the pork production chain. From 764 samples, 31 (4.05%) were stx positive by PCR screening. At farms, 2.86% of samples were stx positive; at slaughter, 4.08% of carcasses were stx positive and at boning rooms, 6% of samples were stx positive. These percentages decreased in pork meat ready for sale at sales markets (4.59%). From positive samples, 50 isolates could be characterized. At farms 37.5% of the isolates carried stx1/stx2 genes, 37.5% possessed stx2e and 25%, carried only stx2. At slaughter we detected 50% of isolates positive for stx2, 33% for stx2e, and 16% for stx1/stx2. At boning rooms 59% of the isolates carried stx1/stx2, 14% stx2e, and 5% stx1/stx2/stx2e. At retail markets 66% of isolates were positive for stx2, 17% stx2e, and 17% stx1/stx2. For the other virulence factors, ehxA and saa were not detected and eae gene was detected in 12% of the isolates. Concerning putative adhesins, agn43 was detected in 72%, ehaA in 26%, aida in 8%, and iha in 6% of isolates. The strains were typed into 14 E. coli O groups (O1, O2, O8, O15, O20, O35, O69, O78, O91, O121, O138, O142, O157, O180) and 10 H groups (H9, H10, H16, H21, H26, H29, H30, H32, H45, H46). This study reports the prevalence and characterization of STEC strains through the chain pork suggesting the vertical transmission. STEC contamination originates in the farms and is transferred from pigs to carcasses in the slaughter process and increase in meat pork at boning rooms and sales markets. These results highlight the need to implement an integrated STEC control system based on good management practices on the farm and critical control point systems in the food chain.

Colonization of Beef Cattle by Shiga Toxin-Producing Escherichia coli during the First Year of Life: A Cohort Study.

Each year Shiga toxin-producing Escherichia coli (STEC) are responsible for 2.8 million acute illnesses around the world and > 250,000 cases in the US. Lowering the prevalence of this pathogen in animal reservoirs has the potential to reduce STEC outbreaks in humans by controlling its entrance into the food chain. However, factors that modulate the colonization and persistence of STEC in beef cattle remain largely unidentified. This study evaluated if animal physiological factors such as age, breed, sex, and weight gain influenced the shedding of STEC in beef cattle. A cohort of beef calves (n = 260) from a multi-breed beef calf population was sampled every three months after birth to measure prevalence and concentration of STEC during the first year of life. Metagenomic analysis was also used to understand the association between the STEC colonization and the composition of gut microflora. This study identified that beef calves were more likely to shed STEC during the first 6 months and that STEC shedding decreased as the animal matured. Animal breed group, sex of the calf, and average weight gain were not significantly associated with STEC colonization. The metagenomic analysis revealed for the first time that STEC colonization was correlated with a lower diversity of gut microflora, which increases as the cattle matured. Given these findings, intervention strategies that segregate younger animals, more likely to be colonized by STEC from older animals that are ready to be harvested, could be investigated as a method to reduce zoonotic transmission of STEC from cattle to humans.

Prevalence and characteristics of Shiga toxin-producing Escherichia coli isolated from retail raw meats in China

Shiga toxin-producing Escherichia coli (STEC) causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome in humans. Most human infections are attributed to consumption of STEC-contaminated foodstuffs of animal origin. In this study, we evaluated the prevalence of STEC from retail raw meats collected from two geographical regions in China. The results revealed that 166 out of 853 samples were stx-positive; 63 STEC isolates were recovered from 58 stx-positive samples including pork (4.4%, 14/318), beef (11.0%, 21/191), mutton (20.6%, 26/126), chicken (0.5%, 1/205), and duck (7.7%, 1/13). Twenty-six O serogroups and 33 O:H serotypes were identified. All three stx1 subtypes and five stx2 subtypes (2a to 2e) were found in the 63 STEC isolates, among which stx2e-positive STEC isolates were the most predominant (39.7%), followed by stx1c only (20.6%), stx1c+stx2b (14.3%), and stx1a only (9.5%). STEC isolates carried virulence genes eae (6.3%), ehxA (36.5%), katP (4.8%), astA (11.1%), and subA (36.5%). Of the four adherence-associated genes tested, toxB was absent, whereas saa, paa, and efa1 were present in 28, three, and one STEC isolates respectively. The STEC isolates were divided into 50 PFGE patterns and 33 sequence types. STEC from different sources and geographical regions were separated by PFGE and MLST. Our results revealed that there is a high genetic diversity of STEC in retail raw meats, some of which have potential to cause human diseases.

Successful detection of pathogenic Shiga-toxin-producing Escherichia coli in shellfish, environmental waters and sediment using the ISO/TS-13136 method.

The presence of highly pathogenic Shiga-toxin-producing Escherichia coli (STEC) in shellfish, upstream waters and sediment from coastal shellfish sites was evaluated using the ISO/TS-13136 method. Shellfish (oysters, mussels and cockles), water and sediment samples were collected monthly over a period of 1 year. The method used real-time PCR detection of stx1, stx2 and eae genes and genetic markers corresponding to the five major serogroups (O157, O26, O103, O111 and O145) on enrichment broths and the identification of STEC when these genes and markers were detected. stx genes were detected in the broth of 33% of shellfish batches (n = 126), 91% of water samples (n = 117) and 28% of sediment (n = 39). One stx1(+), eae(+) O26:H11 strain was isolated from a shellfish batch, and O26:H11, O145:H28 and O103:H2 strains without the stx gene (n = 9) were isolated from shellfish and waters. In conclusion, this study shows the suitability of the ISO/TS-13136 method to assess the presence of highly pathogenic E. coli strains in shellfish farming areas. It also highlights a low prevalence of STEC and consequently suggests a reduced corresponding human health risk. (STEC) infections have been reported following ingestion of contaminated food or water or after bathing in contaminated waters. However, to date, few studies concerning their detection in coastal environment and shellfish have been reported. The aim of this work was to assess the presence of STEC in three shellfish-harvesting areas by the ISO/TS-13136 method, which has recently been used for STEC detection in food.

Association between animal age and the prevalence of Shiga toxin-producing Escherichia coli in a cohort of beef cattle

Even with advancements in pre- and post-harvest food safety, Shiga toxin-producing Escherichia coli (STEC) still present challenges to human health. Since cattle are the primary reservoir for STEC, lowering the prevalence of this pathogen in farm animals may reduce STEC outbreaks in humans. However, because many of the factors that modulate the colonization and persistence of STEC in cattle remain unknown, reducing STEC in this host is challenging. In this study, we evaluated a cohort of beef cattle one to eleven years of age to determine the effect of animal age on the prevalence of STEC. During the first year of sample collection, heifers had significantly lower STEC prevalence than cows (37.5% vs. 70%). In the second year of sample collection, STEC prevalence peaked in cows that were two years of age and tended to decrease as animals became older. In addition, by studying a subset of the animals in both years, we observed an increase in STEC prevalence from 40.6% to 53.1% in heifers, whereas cows had a net decrease in STEC prevalence from 71.4% to 61.9%. The results from this study indicate that animal age is a significant factor that influences the prevalence of STEC in cattle. These findings have implications for the development of on-farm mitigation strategies by targeting animals with the highest risk of shedding; it could be possible to reduce pathogen transmission among cattle and prevent zoonotic or foodborne transmission to humans.

Diversity of Shiga toxin-producing Escherichia coli in sheep flocks of Paraná State, southern Brazil

Sheep constitute an important source of zoonotic pathogens as Shiga toxin-producing Escherichia coli (STEC). In this study, the prevalence, serotypes and virulence profiles of STEC were investigated among 130 healthy sheep from small and medium farms in southern Brazil. STEC was isolated from 65 (50%) of the tested animals and detected in all flocks. A total of 70 STEC isolates were characterized, and belonged to 23 different O:H serotypes, many of which associated with human disease, including hemolytic-uremic syndrome (HUS). Among the serotypes identified, O76:H19 and O65:H– were the most common, and O75:H14 and O169:H7 have not been previously reported in STEC strains. Most of the STEC isolates harbored only stx1, whereas the Stx2b subtype was the most common among those carrying stx2. Enterohemolysin (ehxA) and intimin (eae) genes were detected in 61 (87.1%) and four (5.7%) isolates, respectively. Genes encoding putative adhesins (saa, iha, lpfO113) and toxins (subAB and cdtV) were also observed. The majority of the isolates displayed virulence features related to pathogenesis of STEC, such as adherence to epithelial cells, high cytotoxicity and enterohemolytic activity. Ovine STEC isolates belonged mostly to phylogenetic group B1. PFGE revealed particular clones distributed in some farms, as well as variations in the degree of genetic similarity within serotypes examined. In conclusion, STEC are widely distributed in southern Brazilian sheep, and belonged mainly to serotypes that are not commonly reported in other regions, such as O76:H19 and O65:H–. A geographical variation in the distribution of STEC serotypes seems to occur in sheep.

Prevalence and Resistance Profiles of Enteropathogenic and Shiga ToxinProducing Escherichia coli in Diarrheic Calves in Mashhad and Garmsar Districts, Iran

Background: Shiga toxin-producing Escherichia coli (STEC) strains are considered as one of the most important widespread food-borne pathogens, which cause diarrhea and life threatening diseases, such as hemolytic uremic syndrome, in humans. More recently, the STEC strains have also been incriminated to cause diarrhea and hemorrhagic colitis in calves; enteropathogenic E. coli (EPEC) also causes diarrhea in neonate animals. Objectives: This study aimed to study the prevalence and antibacterial resistance patterns of STEC and EPEC in fecal samples from diarrheic calves in Mashhad and Garmsar districts, Iran. Materials and Methods: A total of 115 fecal samples were collected from diarrheic animals, 75 from Mashhad and 40 from Garmsar districts. A total of 146 E. coli isolates were obtained from culture and subjected to multiplex-PCR assay targeting stx1, stx2, eaeA and ehly virulence genes. The antibacterial resistance patterns of the virulence-positive isolates were determined using disc diffusion method. Results: Eight samples (6.9%) carried the strains with positive results for at least one of the tested virulence genes. Five samples (4.3%) contained the stx-positive strains (STEC) and three (2.6%) carried the eaeA-positive and stx-negative strains, which were categorized as EPEC. In nine virulence-positive E. coli isolates, stx1 (n = 6) was the predominant virulence gene, followed by ehly (n = 5), eae (n = 4), and stx2 (n = 2). Antibacterial resistance patterns of virulence-positive isolates were also determined and nine resistance profiles were discriminated; higher rates of resistance were observed in isolates from Mashhad. Conclusions: This study indicated that other pathologic factors might play a more important role in calf diarrhea in the studied areas, but public health significance of these strains should not be overlooked.

Genotypes and phenotypes of Shiga toxin-producing Escherichia coli (STEC) in Abeokuta, Southwestern Nigeria.

PurposeTo characterize the prevalence of hemolytic Shiga toxin-producing Escherichia coli (STEC) with a multidrug-resistant pattern in different age groups in Abeokuta, Nigeria.MethodsNonrepetitive E. coli isolates were collected from 202 subjects with or without evidence of diarrhea. Each isolate was biochemically identified and antimicrobial susceptibility testing was performed using the disk diffusion method. A sorbitol fermentation test of all the E. coli isolates was done and the minimum inhibitory concentration of suspected STEC was measured by the standard broth microdilution method to determine antibiotic resistance. The genotypes of stx1, stx2, and hlyA were determined by polymerase chain reaction assay.ResultsThe majority of subjects were aged ≥40 years (41.6%) and were female (61.9%). Of the 202 subjects, 86.1% had STEC isolates (P<0.05). A high rate of STEC isolates resistant to amoxicillin (90.6%), cefotaxime (77.7%), and cefuroxime (75.7%) was observed. Resistance to amoxicillin, gentamicin, and cefotaxime was demonstrated with a minimum inhibitory concentration >16 μg/mL in 13.9%, 11.4%, and 10.4% of the isolates, respectively. The prevalence of stx1, stx2, and hlyA was 13.9%, 6.9%, and 2.0%, respectively; 5.5% of stx1 were in the 0–10-year-old age group, 3.5% of stx2 were aged ≥40 and above, and 1.0% of the hlyA isolates were in the 0–10-year-old age group.ConclusionThe prevalence of virulent STEC is a public health concern. The use of polymerase chain reaction assay should aid quick detection of this virulent serotype and help curb the severe epidemic of human diseases associated with STEC infections.

Identification of O Serotypes, Genotypes, and Virulotypes of Shiga Toxin-Producing Escherichia coli Isolates, Including Non-O157 from Beef Cattle in Japan

Bovines are recognized as an important reservoir of Shiga toxin-producing Escherichia coli (STEC). Although STEC strains are significant foodborne pathogens, not all of the STEC held by cattle are pathogenic, and which type of STEC that will become epidemic in humans is unpredictable. Information about the prevalence of serotype and virulence gene distribution in beef cattle is insufficient to develop monitoring and controlling activities for a food safety and security program. Thus, this study investigated the prevalence of O157 and non-O157 STEC in Japanese beef cattle and characterized the isolates by the type of O antigen and several virulence markers to help predict the pathogenicity. In this study, 64.2% (176 of 274) of enrichment cultures of fecal samples collected from an abattoir and farms were stx1 and/or stx2 positive by PCR. STEC strains were isolated from 22.1% (39 of 176) of the positive fecal samples, and these isolates represented 17 types of O antigen (O1, O2 or O50, O5, O8, O55, O84, O91, O109, O113, O136, O150, O156, O157, O163, O168, O174, and O177). Two selective media targeting major STEC groups, cefixime-tellurite sorbitol MacConkey agar and CHROMagar O26/O157, allowed isolation of a variety of STEC strains. The most frequently isolated STEC was O113 (8 of 39), which has previously been reported as a cause of foodborne infections. Although most of the O113 STEC isolated from infected patients possessed the enterohemolysin (hlyA) gene, none of the O113 STEC cattle isolates possessed the hlyA gene. The second most common isolate was O157 (6 of 39), and all these isolates contained common virulence factors, including eae, tir, lpf1, lpf2, and hlyA. This study shows the prevalence of O157 and non-O157 STEC in Japanese beef cattle and the relationship of O antigen and virulotypes of the isolates. This information may improve identification of the source of infection, developing surveillance programs or the current understanding of virulence factors of STEC infections.

Isolation and Characterization of Shiga Toxin-Producing Escherichia coli Serogroups O26, O45, O103, O111, O113, O121, O145, and O157 Shed from Range and Feedlot Cattle from Postweaning to Slaughter

Cattle are the main reservoirs for Shiga toxin-producing Escherichia coli (STEC) strains. E. coli O26, O45, O103, O111, O121, O145, and O157 are among the STEC serogroups that cause severe foodborne illness and have been declared as adulterants by the U.S. Department of Agriculture, Food Safety and Inspection Service. The objectives of this study were (i) to estimate the prevalence of non-O157 STEC and E. coli O157 in naturally infected beef cows and in steer calves at postweaning, during finishing, and at slaughter and (ii) to test non-O157 STEC isolates for the presence of virulence genes stx1, stx2, eaeA, and ehlyA. Samples were collected from study animals during multiple sampling periods and included fecal grabs, rectal swabs, and midline sponge samples. Laboratory culture, PCR, and multiplex PCR were performed to recover and identify E. coli and the virulence genes. The prevalence of non-O157 STEC (serogroups O26, O45, O103, O111, O121, O113, and O145) fecal shedding ranged from 8% (4 of48 samples) to 39% (15 of 38 samples) in cows and 2% (1 of 47 samples) to 38% (9 of 24 samples) in steer calves. The prevalence of E. coli O157 fecal shedding ranged from 0% (0 of 38 samples) to 52% (25 of 48 samples) in cows and 2% (1 of 47 samples) to 31% (15 of 48 samples) in steer calves. In steer calves, the prevalence of non-O157 STEC and E. coli O157 was highest at postweaning, at 16% (15 of 96 samples) and 23% (22 of 96 samples), respectively. Among the 208 non-O157 STEC isolates, 79% (164 isolates) had stx1, 79% (165 isolates) had stx2, and 58% (121 isolates) had both stx1 and stx2 genes. The percentage of non-O157 STEC isolates encoding the eaeA gene was low; of the 165 isolates tested, 8 (5%) were positive for eaeA and 135 (82%) were positive for ehlyA. Findings from this study provide further evidence of non-O157 STEC shedding in beef cows and steer calves particularly at the stage of postweaning and before entry into the feedlot.

Occurrence and characterization of Shiga toxin-producing Escherichia coli O157:H7 and other non-sorbitol-fermenting E. coli in cattle and humans in urban areas of Morogoro, Tanzania.

Escherichia coli strains such as Shiga toxin-producing E. coli (STEC), enteropathogenic E. coli, enterotoxigenic, attaching, and effacing E. coli, and enteroinvasive E. coli cause diarrhea in humans. Although other serotypes exist, the most commonly reported STEC in outbreaks is O157:H7. A cross-sectional study was conducted to isolate and characterize non-sorbitol-fermenting (NSF) E. coli O157:H7 from urban and periurban livestock settings of Morogoro, Tanzania. Human stool, cattle feces, and soil and water samples were collected. Observations and questionnaire interview studies were used to gather information about cattle and manure management practices in the study area. E. coli were isolated on sorbitol MacConkey agar and characterized by conventional biochemical tests. Out of 1049 samples, 143 (13.7%) yielded NSF E. coli. Serological and antimicrobial tests and molecular typing were performed to NSF E. coli isolates. These procedures detected 10 (7%) pathogenic E. coli including STEC (n=7), enteropathogenic E. coli (EPEC) (n=2), and attaching and effacing E. coli (A/EEC) (n=1) strains. The STEC strains had the ability to produce VT1 and different VT2 toxin subtypes that caused cytopathic effects on Vero cells. The prevalence of STEC in cattle was 1.6%, out of which 0.9% was serotype O157:H7 and the overall prevalence of diarrheagenic E. coli in cattle was 2.2%. The serotypes O157:H7, O142:H34, O113:H21, O+:H-, O+:H16, and O25:H4 were identified. One ESBL-producing isolate showed the MLST type ST131. To our knowledge, this is the first finding in Tanzania of this recently emerged worldwide pandemic clonal group, causing widespread antimicrobial-resistant infections, and adds knowledge of the geographical distribution of ST131. Cattle manure was indiscriminately deposited within residential areas, and there was direct contact between humans and cattle feces during manure handling. Cattle and manure management practices expose humans, animals, and the environment to pathogenic E. coli and other manure-borne pathogens. Therefore, there is a need to improve manure management practices in urban and periurban areas to prevent pathogen spread and associated human health risks.

Advances in detection methods for Shiga toxin-producing Escherichia coli (STEC).

Advances in detection methods for Shiga toxin-producing Escherichia coli (STEC).

Shiga Toxin–Producing Escherichia coli Distribution and Characterization in a Pasture-Based Cow-Calf Production System

Shiga toxin–producing Escherichia coli (STEC) strains are commonly found in cattle gastrointestinal tracts. In this study, prevalence and distribution of E. coli virulence genes (stx1, stx2, hlyA, and eaeA) were assessed in a cow-calf pasture-based production system. Angus cows (n = 90) and their calves (n = 90) were kept in three on-farm locations, and fecal samples were collected at three consecutive times (July, August, and September 2011). After enrichment of samples, stx1, stx2, eaeA, and hlyA were amplified and detected with a multiplex PCR (mPCR) assay. Fecal samples positive for stx genes were obtained from 93.3% (84 of 90) of dams and 95.6% (86 of 90) of calves at one or more sampling times. Age class (dam or calf), spatial distribution of cattle (farm locations B, H, K), and sampling time influenced prevalence and distribution of virulence genes in the herd. From 293 stx-positive fecal samples, 744 E. coli colonies were isolated. Virulence patterns of isolates were determined through mPCR assay: stx1 was present in 41.9% (312 of 744) of the isolates, stx2 in 6.5% (48 of 744), eaeA in 4.2% (31 of 744), and hlyA in 2.4% (18 of 744). Prevalence of non-O157 STEC was high among the isolates: 33.8% (112 of 331) were STEC O121, 3.6% (12 of 331) were STEC O103, and 1.8% (6 of 331) were STEC O113. One isolate (0.3%) was identified as STEC O157. Repetitive element sequence–based PCR (rep-PCR) fingerprinting was used to study genetic diversity of stx-positive E. coli isolates. Overall, rep-PCR fingerprints were highly similar, supporting the hypothesis that strains are transmitted between animals but not necessarily from a dam to its calf. Highly similar STEC isolates were obtained at each sampling time, but isolates obtained from dams were more diverse than those from calves, suggesting that strain differences in transference may exist. Understanding the transfer of E. coli from environmental and animal sources to calves may aid in developing intervention strategies to reduce E. coli colonization of young cattle.

Prevalence of shiga toxin producing Escherichia coli, Salmonella enterica, and Listeria monocytogenes at public access watershed sites in a California Central Coast agricultural region

Produce contaminated with enteric pathogens is a major source of foodborne illness in the United States. Lakes, streams, rivers, and ponds were sampled with Moore swabs bi-monthly for over 2 years at 30 locations in the vicinity of a leafy green growing region on the Central California Coast and screened for Shiga toxin producing Escherichia coli (STEC), Salmonella enterica, and Listeria monocytogenes to evaluate the prevalence and persistence of pathogen subtypes. The prevalence of STEC from 1386 samples was 11%; 110 samples (8%) contained E. coli O157:H7 with the highest prevalence occurring close to cattle operations. Non-O157 STEC isolates represented major clinical O-types and 57% contained both shiga toxin types 1 and 2 and intimin. Multiple Locus Variable Number Tandem Repeat Analysis of STEC isolates indicated prevalent strains during the period of study. Notably, Salmonella was present at high levels throughout the sampling region with 65% prevalence in 1405 samples resulting in 996 isolates with slightly lower prevalence in late autumn. There were 2, 8, and 14 sites that were Salmonella-positive over 90, 80, and 70% of the time, respectively. The serotypes identified most often were 6,8:d:-, Typhimurium, and Give. Interestingly, analysis by Pulsed Field Gel Electrophoresis indicated persistence and transport of pulsotypes in the region over several years. In this original study of L. monocytogenes in the region prevalence was 43% of 1405 samples resulting in 635 individual isolates. Over 85% of the isolates belonged to serotype 4b with serotypes 1/2a, 1/2b, 3a, 4d with 4e representing the rest, and there were 12 and 2 sites that were positive over 50 and 80% of the time, respectively. Although surface water is not directly used for irrigation in this region, transport to the produce can occur by other means. This environmental survey assesses initial contamination levels toward an understanding of transport leading to produce recalls or outbreaks.

Isolation, prevalence, and risk factors for infection by shiga toxin-producing Escherichia coli (STEC) in dairy cattle

Rectal swabs of 198 Holstein × Gir crossbred beef cattle from 34 milk farms in the central west of Brazil were analyzed from August 2010 to February 2011. Strains of shiga toxin-producing Escherichia coli (STEC) were isolated from 72.73% (144/198) of the animals, on over 97% of the surveyed properties. The molecular characterization indicated the most common toxin gene stx1 in 70.88% of the animals (202/285), followed by 18.95% (54/285) stx1/sxt2, and 10.18% (29/285) stx2. The presence of STEC in animals together with the probable risk factors based on a questionnaire was evaluated in the owners of the evaluated animals. Results showed that the animal category "calves" and production/technification scale "low" of the farm were related to high STEC prevalence in cattle. The season did not significantly affect the presence of STEC in cattle. The STEC strains are considered a major pathogen, causing severe and potentially lethal diseases in humans such as hemorrhagic colitis and hemolytic uremic syndrome. This high prevalence of STEC in dairy cattle poses a significant risk to public health, since these microorganisms can contaminate products intended for human consumption, e.g., water, raw and pasteurized milk, meat products, dairy products, and/or products of plant origin.