High occurrence of Shiga toxin-producing Escherichia coli (STEC) in healthy cattle in Rio de Janeiro State, Brazil

Occurrence, serotypes and virulence characteristics of Shiga toxin-producing and Enteropathogenic Escherichia coli isolates from dairy cattle in South Africa

Shiga toxin-producing and Enteropathogenic Escherichia coli are foodborne pathogens commonly associated with diarrheal disease in humans. This study investigated the presence of STEC and EPEC in 771 dairy cattle fecal samples which were collected from 5 abattoirs and 9 dairy farms in South Africa. STEC and EPEC were detected, isolated and identified using culture and PCR. Furthermore, 339 STEC and 136 EPEC isolates were characterized by serotype and major virulence genes including stx1, stx2, eaeA and hlyA and the presence of eaeA and bfpA in EPEC. PCR screening of bacterial sweeps which were grown from fecal samples revealed that 42.2% and 23.3% were STEC and EPEC positive, respectively. PCR serotyping of 339 STEC and 136 EPEC isolates revealed 53 different STEC and 19 EPEC serotypes, respectively. The three most frequent STEC serotypes were O82:H8, OgX18:H2, and O157:H7. Only 10% of the isolates were classified as "Top 7" STEC serotypes: O26:H2, 0.3%; O26:H11, 3.2%; O103:H8, 0.6%; and O157:H7, 5.9%. The three most frequent EPEC serotypes were O10:H2, OgN9:H28, and O26:H11. The distribution of major virulence genes among the 339 STEC isolates was as follows: stx1, 72.9%; stx2, 85.7%; eaeA, 13.6% and hlyA, 69.9%. All the 136 EPEC isolates were eaeA-positive but bfpA-negative, while 46.5% carried hlyA. This study revealed that dairy cattle are a major reservoir of STEC and EPEC in South Africa. Further comparative studies of cattle and human STEC and EPEC isolates will be needed to determine the role played by dairy cattle STEC and EPEC in the occurrence of foodborne disease in humans.Please kindly check and confirm the country and city name in affiliation [6].This affiliation is correct.Please kindly check and confirm the affiliationsConfirmed. All Affiliations are accurate.

Shiga toxin-producing Escherichia coli in the animal reservoir and food in Brazil

Shiga toxin-producing Escherichia coli (STEC) is a zoonotic pathotype associated with human gastrointestinal disease that may progress to severe complications. Ruminants, especially cattle, are the main reservoirs of STEC contaminating the environment and foods of animal or vegetable origin. Besides Shiga toxin, other virulence factors are involved in STEC virulence. O157:H7 remains the most frequent serotype associated with disease. In Brazil, the prevalence of STEC reaches values as high as 90% in cattle and 20% in meat products which may impact the Brazilian food export trade. However, only few reports are related to human disease. The stx1 gene prevails in cattle, whereas the stx2 gene is more frequent in food. Several STEC serotypes have been isolated from cattle and food in Brazil, including the O157:H7, O111:NT, NT:H19 as well as O26 and O103 serogroups. O113: H21 STEC strains are frequent in ruminants and foods but with no report in human disease. The virulence profile of Brazilian STEC strains from cattle and food suggests a pathogenic potential to humans, although some differences with clinical strains have been detected. Further studies, employing recent and more discriminative techniques are in need to better clarify their virulence potential.

DIARRHEAGENIC Escherichia coli IN RAW MILK, WATER, AND CATTLE FECES IN NON-TECHNIFIED DAIRY FARMS

Abstract This study focused on detecting diarrheagenic Escherichia coli, enteropathogenic E. coli (EPEC), Shiga-toxin-producing E. coli (STEC), enterohemorrhagic E. coli (EHEC or STEC:EPEC), enterotoxigenic E. coli (ETEC), and enteroaggregative E. coli (EAEC) in raw milk, water, and cattle feces sampled from non-technified dairy farms located in the northeastern São Paulo State, Brazil. Thirty-six water samples were collected at different points, namely, water wells (8 samples), water intended for human consumption (8 samples), water from milking parlor (8 samples), and water intended for animal consumption (7 samples), headwaters (1 sample), rivers (3 samples), and reservoirs (1 sample). Three raw milk samples were taken directly from bulk tanks in each farm, totalizing 24 samples. Feces samples were collected using rectal swabs from 160 bovines (20 animals per farm). E. coli was detected in 128 feces samples (80%), 16 raw milk samples (66.67%), and 20 water samples (55.56%). STEC (26 samples, 16.25%), EPEC (10 samples, 6.25%), STEC: EPEC (5 samples, 3.13%), and STEC: ETEC (1 sample, 0.63%) were the most prevalent strains detected in samples from cattle feces. EPEC, STEC, and STEC: EPEC strains were detected in 4.17% (1 sample), 16.67% (4 samples), and 4.17% (1 sample) of raw milk samples, respectively. STEC strains were detected in water used in the milking parlor, while no EAEC strain was detected. As a conclusion, cattle feces are important contamination sources of pathogenic E. coli in non-technified dairy farms and, consequently, cross-contamination among feces, water, and/or raw milk can occur. The use of quality water and hygienic practices during milking are recommended to avoid contamination since pathogens can be transmitted to humans via raw milk or raw milk cheese ingestion.

Multi-Year Persistence of Verotoxigenic Escherichia coli (VTEC) in a Closed Canadian Beef Herd: A Cohort Study

In this study, fecal samples were collected from a closed beef herd in Alberta, Canada from 2012 to 2015. To limit serotype bias, which was observed in enrichment broth cultures, Verotoxigenic Escherichia coli (VTEC) were isolated directly from samples using a hydrophobic grid-membrane filter verotoxin immunoblot assay. Overall VTEC isolation rates were similar for three different cohorts of yearling heifers on both an annual (68.5 to 71.8%) and seasonal basis (67.3 to 76.0%). Across all three cohorts, O139:H19 (37.1% of VTEC-positive samples), O22:H8 (15.8%) and O?(O108):H8 (15.4%) were among the most prevalent serotypes. However, isolation rates for serotypes O139:H19, O130:H38, O6:H34, O91:H21, and O113:H21 differed significantly between cohort-years, as did isolation rates for some serotypes within a single heifer cohort. There was a high level of VTEC serotype diversity with an average of 4.3 serotypes isolated per heifer and 65.8% of the heifers classified as "persistent shedders" of VTEC based on the criteria of >50% of samples positive and ≥4 consecutive samples positive. Only 26.8% (90/336) of the VTEC isolates from yearling heifers belonged to the human disease-associated seropathotypes A (O157:H7), B (O26:H11, O111:NM), and C (O22:H8, O91:H21, O113:H21, O137:H41, O2:H6). Conversely, seropathotypes B (O26:NM, O111:NM) and C (O91:H21, O2:H29) strains were dominant (76.0%, 19/25) among VTEC isolates from month-old calves from this herd. Among VTEC from heifers, carriage rates of vt1, vt2, vt1+vt2, eae, and hlyA were 10.7, 20.8, 68.5, 3.9, and 88.7%, respectively. The adhesin gene saa was present in 82.7% of heifer strains but absent from all of 13 eae+ve strains (from serotypes/intimin types O157:H7/γ1, O26:H11/β1, O111:NM/θ, O84:H2/ζ, and O182:H25/ζ). Phylogenetic relationships inferred from wgMLST and pan genome-derived core SNP analysis showed that strains clustered by phylotype and serotype. Further, VTEC strains of the same serotype usually shared the same suite of antibiotic resistance and virulence genes, suggesting the circulation of dominant clones within this distinct herd. This study provides insight into the diverse and dynamic nature of VTEC populations within groups of cattle and points to a broad spectrum of human health risks associated with these E. coli strains.

Detection and Quantification of Seven Major Serogroups of Shiga Toxin-Producing Escherichia coli on Hides of Cull Dairy, Cull Beef, and Fed Beef Cattle at Slaughter†

Dehiding during beef cattle processing can introduce fecal contaminants, including Shiga toxin-producing Escherichia coli (STEC), from hides onto carcass surfaces, creating the potential for contaminated beef. Fecal shedding of major STEC serogroups (O26, O45, O103, O111, O121, O145, and O157; STEC-7) may differ among cattle populations, yet no study has been conducted to isolate STEC-7 on hides of multiple cattle types on the same production days at the same processing plant. Our objective was to estimate and compare prevalence and concentrations of STEC-7 on hides of cull dairy, cull beef, and fed beef cattle from the same date and processing plant. Overall, 1,500 cattle hides were sponge sampled from cull dairy ( n = 500), cull beef ( n = 500) and fed beef cattle ( n = 500) over 10 processing days. To determine prevalence, samples were subjected to an immunomagnetic separation culture method, and presumptive STEC isolates were tested by PCR for serogroup and major virulence genes. A spiral plate method was used to enumerate STEC-7 from hide samples. Data were analyzed with linear mixed models. All STEC-7 serogroups except O121 were detected and quantified on cattle hides in this study population. Slightly more fed beef hides (77 of 500; 15.4%) and cull beef hides (76 of 500; 15.2%) were positive for at least one STEC-7 strain compared with cull dairy hides (57 of 500; 11.4%), but cattle type was not significantly associated ( P = 0.19) with STEC-7 prevalence. Fed beef hides had a significantly higher prevalence ( P < 0.05) of STEC O103, O145, and O157 serogroups than did either of the other cattle types. The highest proportions of quantifiable samples were for STEC O145 (32 of 1,500 samples; 2.1%) and O157 (31 of 1,500 samples; 2.1%) serogroups, with the majority of concentrations at 3 to 5 and 2 to 4 log CFU/100 cm² of hide, respectively. Results indicate that hide contamination with some major STEC serogroups differs significantly among cattle types at harvest, even within the same day and location.

Antibodies to Shiga toxins in Brazilian cattle

Cattle are considered a reservoir of Shiga toxin-producing Escherichia coli (STEC). There is no information about the presence of antibodies against Shiga toxins in Brazilian bovine serum. Using ELISA, all sera tested showed antibodies against the two main STEC virulence factors; Stx1 and Stx2. Neutralizing antibodies against Stx1 and/or Stx2 were detected in all but one serum. In conclusion, our results indicated that these animals had been exposed to STEC producing both toxins.

Current Interventions for Controlling Pathogenic Escherichia coli

This review examined scientific reports and articles published from 2007 to 2016 regarding the major environmental sources of pathogenic Escherichia coli and the routes by which they enter the human gastrointestinal tract. The literature describes novel techniques used to combat pathogenic E. coli transmitted to humans from livestock and agricultural products, food-contact surfaces in processing environments, and food products themselves. Although prevention before contamination is always the best "intervention," many studies aim to identify novel chemical, physical, and biological techniques that inactivate or eliminate pathogenic E. coli cells from breeding livestock, growing crops, and manufactured food products. Such intervention strategies target each stage of the food chain from the perspective of "Farm to Table food safety" and aim to manage major reservoirs of pathogenic E. coli throughout the entire process. Issues related to, and recent trends in, food production must address not only the safety of the food itself but also the safety of those who consume it. Thus, research aims to discover new "natural" antimicrobial agents and to develop "multiple hurdle technology" or other novel technologies that preserve food quality. In addition, this review examines the practical application of recent technologies from the perspective of product quality and safety. It provides comprehensive insight into intervention measures used to ensure food safety, specifically those aimed at pathogenic E. coli.

Evidence for the benefits of food chain interventions on E. coli O157:H7/NM prevalence in retail ground beef and human disease incidence: A success story

OBJECTIVES

Human infection with Escherichia coli O157:H7/NM has historically been associated with consumption of undercooked ground beef. The purpose of this paper is to investigate the correlation of the decline in E. coli O157:H7/NM infections in Canada with the introduction of control efforts in ground beef by industry.

METHODS

The human incidence of E. coli O157:H7/NM, prevalence in ground beef and interventions from 1996 to 2014 were analyzed. Pathogen prevalence data were obtained from federal government and industry surveillance and inspection/compliance programs. A survey of the largest ground beef producers in Canada was conducted to identify when interventions were implemented.

RESULTS

The incidence of E. coli O157:H7/NM infections in Canada declined from ≈4 cases/100 000 to ≈1 case/100000 from 2000 to 2010. Verotoxigenic Escherichia coli (VTEC) prevalence in ground beef sold at retail declined from about 30% around the year 2000 to <2% since 2012. Other measures of the prevalence of E. coli, VTEC, and E. coli O157:H7/NM in beef and ground beef also declined. The number and types of interventions implemented in the major beef processing establishments in Canada increased from 1996 to 2016.

CONCLUSION

The observed decline in human illnesses and pathogen levels in relation to retail meats was associated with the introduction of control efforts by industry, federal and provincial/territorial governments, and the general population. Industry-led changes in beef processing along with the introduction of food safety policies, regulations, and public education have led to improved food safety in Canada.

Serotypes, virulence markers and cell invasion ability of Shiga toxin-producing Escherichia coli strains isolated from healthy dairy cattle

AIM

The occurrence of virulence markers, serotypes and invasive ability were investigated in Shiga toxin-producing Escherichia coli (STEC) isolated from faecal samples of healthy dairy cattle at Rio de Janeiro State, Brazil.

METHODS AND RESULTS

From 1562 stx-positive faecal samples, 105 STEC strains were isolated by immuno-magnetic separation (IMS) or plating onto MacConkey agar (MC) followed by colony hybridisation. Fifty (47·6%) strains belonged to nine serotypes (O8:H19, O22:H8, O22:H16, O74:H42, O113:H21, O141:H21, O157:H7, O171:H2 and ONT:H21). The prevalent serotypes were O157:H7 (12·4%), O113:H21 (6·7%) and O8:H19 (5·7%). Virulence genes were identified by polymerase chain reaction (PCR). E-hlyA (77·1%) was the more prevalent virulence marker, followed by espP (64·8%), saa (39%), eae (24·8%) and astA (21·9%). All O157:H7 strains carried the γ (gamma) variant of the locus of enterocyte effacement (LEE) genes and the stx2c gene, while the stx1/stx2 genotype prevailed among the eae-negative strains. None of the eae-positive STEC produced the localized adherence (LA) phenotype in HEp-2 or Caco-2 cells. However, intimate attachment (judged by the fluorescent actin staining test) was detected in some eae-positive strains, both in HEp-2 (23·1%) and in Caco-2 cells (11·5%). Most strains (87·5%) showed 'peripheral association' (PA) adherence phenotype to undifferentiated Caco-2 cells. Twenty-five (92·6%) of 27 strains invaded Caco-2 cells. The highest average value of invasion (9·6%) was observed among the eae-negative bovine strains from serotypes described in human disease.

CONCLUSION

Healthy dairy cattle is a reservoir of STEC carrying virulence genes and properties associated with human disease.

SIGNIFICANCE AND IMPACT OF THE STUDY

Although reports of human disease associated with STEC are scarce in Brazil, the colonization of the animal reservoir by potentially pathogenic strains offers a significant risk to our population.

Patotipos de Escherichia coli causadores de diarreia em bezerros: uma atualização

A diarreia é uma das doenças mais frequentes de bezerros com até 30 dias de idade e é uma importante causa de perdas econômicas. Sua etiologia é complexa e envolve a interação de diversos fatores infecciosos, nutricionais, imunológicos, gerenciais e ambientais. Os principais sinais clínicos são a diarreia, desidratação progressiva, acidose metabólica, desequilíbrio de eletrólitos e balanço energético negativo com ou sem hipoglicemia, que se não tratados, levam à morte do animal. Escherichia coli se destaca como um importante enteropatógeno envolvido na síndrome diarreica. Cepas de E. coli patogênicas são classificadas em grupos ou patotipos, de acordo com a produção de fatores de virulência e mecanismos pelos quais causam doença. Já foram identificados cinco patotipos de E. coli associados à diarreia em bezerros: E. coli enterotoxigênica (ETEC), E. coli enteropatogênica (EPEC), E. coli enterohemorrágica (EHEC), E. coli produtora de toxina Shiga (STEC) e E. coli necrotoxigênica (NTEC). Nesse artigo apresentamos as principais características e os atuais conhecimentos sobre os patotipos de E. coli causadores de diarreia em bezerros.

Animal Reservoirs of Shiga Toxin-Producing Escherichia coli

Shiga toxin-producing Escherichia coli (STEC) strains have been detected in a wide diversity of mammals, birds, fish, and several insects. Carriage by most animals is asymptomatic, thus allowing for dissemination of the bacterium in the environment without detection. Replication of the organism may occur in the gastrointestinal tract of some animals, notably ruminants. Carriage may also be passive or transient, without significant amplification of bacterial numbers while in the animal host. Animals may be classified as reservoir species, spillover hosts, or dead-end hosts. This classification is based on the animal's ability to (i) transmit STEC to other animal species and (ii) maintain STEC infection in the absence of continuous exposure. Animal reservoirs are able to maintain STEC infections in the absence of continuous STEC exposure and transmit infection to other species. Spillover hosts, although capable of transmitting STEC to other animals, are unable to maintain infection in the absence of repeated exposure. The large diversity of reservoir and spillover host species and the survival of the organism in environmental niches result in complex pathways of transmission that are difficult to interrupt.

Occurrence of Shiga-toxigenic Escherichia coli in Stomoxys calcitrans (Diptera: Muscidae)

This study aimed to verify the occurrence of Shiga toxin-producing Escherichia coli (STEC) strains in three distinct anatomic parts of the stable fly Stomoxys calcitrans by multiplex polymerase chain reaction (PCR Multiplex). According to the results obtained, E. coli was identified in 19.5% of the stable flies. Shiga toxin genes were detected in 13% of the E. coli isolated, most frequently from the surface, followed by abdominal digestive tract and mouth apparatus of insects, respectively. This is the first study to detect presence of STEC in Stomoxys calcitrans in Brazil; it has also revealed the potential role of stable flies as carriers of pathogenic bacterial agents.

PCR and ELISA (VIDAS ECO O157(®)) Escherichia coli O157:H7 identification in Minas Frescal cheese commercialized in Goiânia, GO

Escherichia coli O157:H7 has been incriminated in food poisoning outbreaks and sporadic cases of hemorrhagic colitis and hemolytic uremic syndrome in many countries. Considering the high susceptibility of Minas Frescal cheese to contamination by E. coli O157:H7, the aim of this study was to determine the occurrence of this pathogen through PCR (Polymerase Chain Reaction) and ELISA (VIDAS ECO O157^®, bioMérieux, Lyon, France) test. Thirty cheese samples manufactured by artisan farmhouse producers were collected from open-air markets in Goiânia and thirty from industries under Federal Inspection located in Goiás State which trade their products in supermarkets in Goiânia. E. coli O157:H7 was detected in 6.67% samples collected in open air markets using ELISA, and 23,33% with PCR. The pathogen was not detected in samples from industries under Federal Inspection.

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.

Regional variation in the prevalence of E. coli O157 in cattle: a meta-analysis and meta-regression

BACKGROUND

Escherichia coli O157 (EcO157) infection has been recognized as an important global public health concern. But information on the prevalence of EcO157 in cattle at the global and at the wider geographical levels is limited, if not absent. This is the first meta-analysis to investigate the point prevalence of EcO157 in cattle at the global level and to explore the factors contributing to variation in prevalence estimates.

METHODS

Seven electronic databases- CAB Abstracts, PubMed, Biosis Citation Index, Medline, Web of Knowledge, Scirus and Scopus were searched for relevant publications from 1980 to 2012. A random effect meta-analysis model was used to produce the pooled estimates. The potential sources of between study heterogeneity were identified using meta-regression.

PRINCIPAL FINDINGS

A total of 140 studies consisting 220,427 cattle were included in the meta-analysis. The prevalence estimate of EcO157 in cattle at the global level was 5.68% (95% CI, 5.16-6.20). The random effects pooled prevalence estimates in Africa, Northern America, Oceania, Europe, Asia and Latin America-Caribbean were 31.20% (95% CI, 12.35-50.04), 7.35% (95% CI, 6.44-8.26), 6.85% (95% CI, 2.41-11.29), 5.15% (95% CI, 4.21-6.09), 4.69% (95% CI, 3.05-6.33) and 1.65% (95% CI, 0.77-2.53), respectively. Between studies heterogeneity was evidenced in most regions. World region (p<0.001), type of cattle (p<0.001) and to some extent, specimens (p = 0.074) as well as method of pre-enrichment (p = 0.110), were identified as factors for variation in the prevalence estimates of EcO157 in cattle.

CONCLUSION

The prevalence of the organism seems to be higher in the African and Northern American regions. The important factors that might have influence in the estimates of EcO157 are type of cattle and kind of screening specimen. Their roles need to be determined and they should be properly handled in any survey to estimate the true prevalence of EcO157.

Enterohemorrhagic Escherichia coli O157: H7 from healthy dairy cattle in Mid-West Brazil: occurrence and molecular characterization

Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 represents the major Shiga toxin-producing E. coli (STEC) strain related to large outbreaks and severe diseases such as hemorrhagic colitis (HC) and the potentially lethal hemolytic uremic syndrome (HUS). The aim of this study was to report the occurrence and molecular characterization of O157:H7 isolates obtained by rectal swab from 52 healthy dairy cattle belonging to 21 farms in Mid-West of Brazil. Detection of 16SrRNA, stx1, stx2, rfbO157, fliCh7, eae, ehxA, saa, cnf1, chuA, yjaA and TSPE4.C2 genes was performed by PCR. The isolates were further characterized by serotyping. Two hundred and sixty E. coli isolates were obtained, of which 126 were characterized as STEC. Two isolates from the same cow were identified as serotype O157:H7. Both isolates presented the stx2, eae, ehxA, saa and cnf1 virulence factor genes and the chuA gene in the phylogenetic classification (virulent group D), suggesting that they were clones. The prevalence of O157:H7 was found to be 1.92% (1/52 animals), demonstrating that healthy dairy cattle from farms in the Mid-West of Brazil are an important reservoir for highly pathogenic E. coli O157:H7.

Escherichia coli O157 in ground beef from local retail markets in Pachuca, Mexico

Escherichia coli O157 strains have been recognized as pathogenic bacteria, of which raw beef is a known vehicle. An evaluation was done of the presence of E. coli O157 in ground beef from local retail markets in Pachuca, Hidalgo State, Mexico. A total of 120 ground beef samples (500 g) were tested for E. coli O157 by simultaneous application of the U. S. Department of Agriculture, Food Safety and Inspection Service (FSIS)'s Microbiology Laboratory Guidebook culture procedure 5.05, and two commercial kits, Reveal for E. coli O157:H7 and Visual Immunoprecipitate Assay (VIP) Gold for enterohemorrhagic E. coli. Two incubation times (8 and 20 h) were used with the commercial kits. Presence of stx1, stx2, and eaeA loci was determined by multiplex PCR. Of 360 subsamples (120 per procedure), 12 samples were found to be E. coli O157 positive by the FSIS culture method. With VIP, 73 subsamples were presumptive positive after 8 h of enrichment, and 60 were presumptive positive after 20 h of enrichment. Of these, only 6 (8 h) and 8 (20 h) subsamples were confirmed true positives with the FSIS method. With Reveal, 60 subsamples were presumptive positive after 8 h of enrichment and 50 were presumptive positive after 20 h of enrichment. Of these, only 6 (8 h) and 8 (20 h) subsamples were confirmed as true positives with the FSIS method. A total of 57 E. coli O157:H7 and 21 E. coli O157 strains were isolated. None of the O157 or O157:H7 strains had stx1 or stx2 loci, and only one had the eaeA locus. To our knowledge, this is the first report of the presence of E. coli O157 in commercial ground beef from Mexico, and the first report of isolation of a large number of stx-negative E. coli O157 and E. coli O157:H7 strains in Mexico.

Reduction of Escherichia coli O157:H7 and Salmonella after application of various sanitizing treatments to harvesting knives

Consumption of food contaminated with Escherichia coli O157:H7 and Salmonella can cause enteric disease in consumers. If not properly sanitized, knives used during animal harvest can spread these and other pathogens. This study evaluated the reduction of E. coli O157:H7 and Salmonella on harvesting knives after nonthermal sanitation. Knives were inoculated in cocktails of E. coli O157:H7 or Salmonella and treated by 30-s immersions in ambient-temperature solutions (unless temperature was specified) of 1.1 % sodium metasilicate (SMS), 200 ppm of quaternary ammonium compounds (QAC), 200 ppm of chlorine (Cl(2)), 5 % lactic acid (LA), 82.2°C water, and 21°C water. Initial and treated counts were determined by plating onto MacConkey and xylose lysine desoxycholate for E. coli O157:H7 and Salmonella, respectively. Initial counts were determined by sampling one side of the knife blade, while treated counts were sampled from the opposite side. Plates were incubated for 24 to 48 h at 37°C. Mean attachment of E. coli O157:H7 and Salmonella was 4.51 and 5.09 log CFU/cm(2), respectively. Mean log reductions on knives inoculated with E. coli O157:H7 were 1.16, 3.51, 3.38, 1.38, 3.82, and 2 0.41 CFU/cm(2) after treatment in SMS, QAC, Cl(2), LA, 82.2°C water, and 21°C water, respectively (P ≤ 0.05). Knives inoculated with Salmonella showed reductions of 0.78, 3.42, 3.40, 2.91, 4.12, and 0.36 log CFU/cm(2) after treatment in SMS, QAC, Cl(2), LA, 82.2°C water, and 21°C water, respectively (P ≤ 0.05). Results indicate that some ambient-temperature sanitizing agents have the potential to significantly reduce E. coli O157:H7 and Salmonella populations on knives used during animal harvest.

[EHEC carriage in ruminants and probiotic effects]

Enterohaemorrhagic Escherichia coli (EHEC) are Shiga-Toxin producing E. coli (STEC) that cause human outbreaks which can lead to a severe illness such as haemolytic-uraemic syndrome (HUS), particularly in young children. The gastrointestinal tract of cattle and other ruminants is the principal reservoir of EHEC strains and outbreaks have been associated with direct contact with the farm environment, and with the consumption of meat, dairy products, water and fruit or vegetable contaminated with ruminant manure. Several outbreaks occurred these last years in France. In Brazil, although STEC carriage in ruminants is important, human cases due to EHEC are fairly rare. In order to reduce EHEC survival in the ruminant gastrointestinal tract and thus limit contamination of food products, it is necessary to determine the mechanisms underlying EHEC persistence in this ecosystem with the aim of developing nutritional or ecological strategies. The effect of probiotics has been tested in vitro on the growth and survival of EHEC strains and in vivo on the animal carriage of these strains. Various studies have then shown that lactic bacteria or non-pathogenic E. coli strains were able to limit EHEC fecal shedding. In addition, understanding EHEC physiology in the ruminant gut is also critical for limiting EHEC shedding. We found that EHEC O157:H7 is able to use ethanolamine and mucus-derived sugars as nitrogen and carbon sources, respectively. Thus, these substrates represent an ecological niche for EHEC and their utilization confers a competitive growth advantage to these pathogens as they use them more rapidly than the bacteria belonging to the resident intestinal microbiota. Understanding EHEC metabolism and ecology in the bovine intestinal tract will allow proposing probiotic strains to compete with EHEC for nutrients and thus decrease the sanitary risk.

Detection of virulence genes in Escherichia coli strains isolated from diarrheic and healthy feces of dairy calves in Brazil

The aim of this work was to test 101 strains of E. coli for virulence factors associated with enterotoxigenic and enterohemorrhagic pathotypes of E. coli isolated from diarrheic and non-diarrheic calves. The virulence factors of E. coli Stx1 (Shiga toxin), Stx2, Ehly (Enterohemolysin), the eae gene, LT-II (heat-labile enterotoxin), STa (heat-stable toxin), and adhesins K99 and F41 were detected by PCR. Serogroups were determined by serological methods and Stx production was observed by biological assays in Vero cells. The frequency of the eae gene was higher in isolates from diarrheic calves (35/58, 60.3%) than in non-diarrheic calves (8/43, 18.6%; P < 0.001). The gene for Stx1 occurred at high frequencies in the diarrheic strains (24/58, 41.3%) as well as in non-diarrheic (19/43, 44.2%) ones and all strains that were Stx positive by PCR showed cytotoxicity in Vero cells. Stx2 was found in ten strains, Ehly in eight strains, and LT-II in only two strains. Twenty-eight strains were negative for all of the PCR assays, including for F41 and K99 adhesins. The serogroups O7, O23, O4, O8, O153 and O156 were observed most frequently. Our results show that strains of E. coli isolated from cattle have similar virulence factors genes to strains isolated from cases of diseases in humans and may be a source of potentially pathogenic STEC for humans.

Application of a real-time PCR-based system for monitoring of O26, O103, O111, O145 and O157 Shiga toxin-producing Escherichia coli in cattle at slaughter

Faecal samples were collected from 573 slaughtered cattle aged between three and 24 months in seven abattoirs. After enrichment (mTSB with novobiocin), samples were screened by real-time PCR first for stx and if positive, tested for the top-five Shiga toxin-producing Escherichia coli (STEC) serogroups using PCR assays targeting genes specific for serogroups O26, O103, O111, O145 and O157. Of 563 samples with available results, 74.1% tested positive for stx genes. Amongst them, the serogroups O145, O103, O26, O157 and O111 were detected in 41.9%, 25.9%, 23.9%, 7.8% and 0.8%, respectively. From 95 O26, 166 O145 and 30 O157 PCR-positive samples, 17 O26, 28 O145 and 12 O157 strains were isolated by colony hybridization after immunomagnetic separation. The 17 O26 strains were eae-positive, but only nine strains harboured stx (eight possessing stx1 and one stx2). Of the 28 O145 strains, ten were eae-positive including four harbouring stx1 or stx2, whereas 18 were negative for stx and eae. Five of the 12 O157 strains harboured stx2 and eae, did not ferment sorbitol, and were identified as STEC O157:H7/H⁻. The other seven O157 strains were negative for stx and eae or positive only for eae. Shiga toxin genes and the top-five STEC serogroups were frequently found in young Swiss cattle at slaughter, but success rates for strain isolation were low and only few strains showed a virulence pattern of human pathogenic STEC.

Shiga toxin: expression, distribution, and its role in the environment

In this review, we highlight recent work that has increased our understanding of the production and distribution of Shiga toxin in the environment. Specifically, we review studies that offer an expanded view of environmental reservoirs for Shiga toxin producing microbes in terrestrial and aquatic ecosystems. We then relate the abundance of Shiga toxin in the environment to work that demonstrates that the genetic mechanisms underlying the production of Shiga toxin genes are modified and embellished beyond the classical microbial gene regulatory paradigms in a manner that apparently "fine tunes" the trigger to modulate the amount of toxin produced. Last, we highlight several recent studies examining microbe/protist interactions that postulate an answer to the outstanding question of why microbes might harbor and express Shiga toxin genes in the environment.

Detection of stx and stx genes in Pennsylvanian white-tailed deer

Shiga toxin-producing E. coli carrying the stx(1) and/or stx(2) genes can cause multi-symptomatic illness in humans. A variety of terrestrial and aquatic environmental reservoirs of stx have been described. Culture based detection of microbes in deer species have found a low percentage of samples that have tested positive for Stx-producing microbes, suggesting that while deer may contain these microbes, their overall abundance in deer is low. In this study, quantitative PCR (qPCR) was utilized to test for the presence of stx genes in white-tailed deer fecal matter in western Pennsylvania. In this culture independent screening, nearly half of the samples tested positive for the stx(2) gene, with a bias towards samples that were concentrated with stx(2). This study, while limited in scope, suggests that deer may be a greater reservoir for stx than was previously thought.

ESCHERICHIA COLI, PRODUTORAS DE SHIGATOXINAS DETECTADAS EM FEZES DE BOVINOS LEITEIROS

RESUMO Este trabalho teve como objetivo determinar a prevalência de Escherichia coli produtoras de Shigatoxinas (STEC) e E. coli dos sorogrupos O157, O111 e O113 em rebanhos leiteiros do Município de Jaboticabal, SP, Brasil. A presença de sequências gênicas stx1, stx2e eae foi detectada pela reação em cadeia da polimerase (PCR) em amostras de fezes. Todas as amostras stx e eae positivas foram submetidas a uma nova reação de PCR para detecção das sequências rfb O157, O111 e O113. Observou-se uma alta prevalência (72,16%) de sequências stx nas fezes dos bovinos, sendo que o perfil genotípico encontrado com maior frequência foi o stx1 associado à stx2. Os coeficientes de prevalência das sequências rfb O157, O111 e O113 foram, respectivamente, 14,77%, 0,2% e 30,83%. Animais de todos os rebanhos (100%) apresentaram em suas fezes STEC e E. coli O113 e os sorogrupos O157 e O111 foram observados em 60,0% e 10,0% dos rebanhos, respectivamente. Concluiu-se que a alta prevalência de STEC detectada em rebanho leiteiro evidenciada nas fezes de bovinos desempenham um papel importante na contaminação ambiental e podem oferecerrisco de agravo à saúde pública.

Escherichia coli O157:H7: animal reservoir and sources of human infection

This review surveys the literature on carriage and transmission of enterohemorrhagic Escherichia coli (EHEC) O157:H7 in the context of virulence factors and sampling/culture technique. EHEC of the O157:H7 serotype are worldwide zoonotic pathogens responsible for the majority of severe cases of human EHEC disease. EHEC O157:H7 strains are carried primarily by healthy cattle and other ruminants, but most of the bovine strains are not transmitted to people, and do not exhibit virulence factors associated with human disease. Prevalence of EHEC O157:H7 is probably underestimated. Carriage of EHEC O157:H7 by individual animals is typically short-lived, but pen and farm prevalence of specific isolates may extend for months or years and some carriers, designated as supershedders, may harbor high intestinal numbers of the pathogen for extended periods. The prevalence of EHEC O157:H7 in cattle peaks in the summer and is higher in postweaned calves and heifers than in younger and older animals. Virulent strains of EHEC O157:H7 are rarely harbored by pigs or chickens, but are found in turkeys. The bacteria rarely occur in wildlife with the exception of deer and are only sporadically carried by domestic animals and synanthropic rodents and birds. EHEC O157:H7 occur in amphibian, fish, and invertebrate carriers, and can colonize plant surfaces and tissues via attachment mechanisms different from those mediating intestinal attachment. Strains of EHEC O157:H7 exhibit high genetic variability but typically a small number of genetic types predominate in groups of cattle and a farm environment. Transmission to people occurs primarily via ingestion of inadequately processed contaminated food or water and less frequently through contact with manure, animals, or infected people.

Biochemical properties, enterohaemolysin production and plasmid carriage of Shiga toxin-producing Escherichia coli strains

Thirty-eight strains of Shiga toxin-producing Escherichia coli (STEC) were characterised in terms of biochemical properties, enterohaemolysin production and plasmid carriage. A wide variation in the biochemical properties was observed among the STEC, with 14 distinct biotypes identified. Biotype 1 was the most common, found in 29% of the strains. Enterohaemolysin production was detected in 29% of the strains. Most of the bacterial strains (95%) carried one or more plasmids and considerable heterogeneity in size and combinations was observed. Seven distinct plasmid profiles were identified. The most common profile, characterised by the presence of a single plasmid of ~90 kb, was found in 50% of these strains. These data indicate extensive diversity among STEC strains. No correlation was found among biotype, serotype, enterohaemolysin production and plasmid profile.

Temporal and spatial patterns of bovine Escherichia coli O157 prevalence and comparison of temporal changes in the patterns of phage types associated with bovine shedding and human E. coli O157 cases in Scotland between 1998-2000 and 2002-2004

Background

Escherichia coli O157 is an important cause of acute diarrhoea, haemorrhagic colitis and, especially in children, haemolytic uraemic syndrome (HUS). Incidence rates for human E. coli O157 infection in Scotland are higher than most other United Kingdom, European and North American countries. Cattle are considered the main reservoir for E. coli O157. Significant associations between livestock related exposures and human infection have been identified in a number of studies.

Results

Animal Studies: There were no statistically significant differences (P = 0.831) in the mean farm-level prevalence between the two studies (SEERAD: 0.218 (95%CI: 0.141-0.32); IPRAVE: 0.205 (95%CI: 0.135-0.296)). However, the mean pat-level prevalence decreased from 0.089 (95%CI: 0.075-0.105) to 0.040 (95%CI: 0.028-0.053) between the SEERAD and IPRAVE studies respectively (P < 0.001). Highly significant (P < 0.001) reductions in mean pat-level prevalence were also observed in the spring, in the North East and Central Scotland, and in the shedding of phage type (PT) 21/28. Human Cases: Contrasting the same time periods, there was a decline in the overall comparative annual reported incidence of human cases as well as in all the major PT groups except 'Other' PTs. For both cattle and humans, the predominant phage type between 1998 and 2004 was PT21/28 comprising over 50% of the positive cattle isolates and reported human cases respectively. The proportion of PT32, however, was represented by few (<5%) of reported human cases despite comprising over 10% of cattle isolates. Across the two studies there were differences in the proportion of PTs 21/28, 32 and 'Other' PTs in both cattle isolates and reported human cases; however, only differences in the cattle isolates were statistically significant (P = 0.002).

Conclusion

There was no significant decrease in the mean farm-level prevalence of E. coli O157 between 1998 and 2004 in Scotland, despite significant declines in mean pat-level prevalence. Although there were declines in the number of human cases between the two study periods, there is no statistically significant evidence that the overall rate (per 100,000 population) of human E. coli O157 infections in Scotland over the last 10 years has altered. Comparable patterns in the distribution of PTs 21/28 and 32 between cattle and humans support a hypothesized link between the bovine reservoir and human infections. This emphasizes the need to apply and improve methods to reduce bovine shedding of E. coli O157 in Scotland where rates appear higher in both cattle and human populations, than in other countries.

Analysis of Escherichia coli isolated from bovine mastitic milk

Mastitis has been recognized for some time as the most costly disease in dairy herds. From February to November 2004, 670 samples of bovine mastitic milk from which 231 Escherichia coli strains were isolated, were collected from two Brazilian states. The strains were screened for the presence of Shiga toxin-producing (stx 1 and stx 2) and intimin (eae) genes. Twenty (8.6%) strains were detected by PCR to harbor the Shiga toxin genes (8 the stx 1 gene, 12 the stx 2 gene and none both of them). Two (0.8%) of the Escherichia coli strains studied were eae positive non Shiga toxin-producing. The strains were also examined for resistance to 12 antimicrobial agents. The predominantly observed resistance was to tetracycline (92.2%), streptomycin (90.4%), nalidixic acid (88.3%), amikacin (86.5%) and cephalothin (84.8%). Multidrug resistance was found among 152 isolates (65.8%).

Escherichia coli O157:H7 colonization in small domestic ruminants

Enterohaemorrhagic Escherichia coli O157:H7 was first implicated in human disease in the early 1980s, with ruminants cited as the primary reservoirs. Preliminary studies indicated cattle to be the sole source of E. coli O157:H7 outbreaks in humans; however, further epidemiological studies soon demonstrated that E. coli O157:H7 was widespread in other food sources and that a number of transmission routes existed. More recently, small domestic ruminants (sheep and goats) have emerged as important sources of E. coli O157:H7 human infection, particularly with the widespread popularity of petting farms and the increased use of sheep and goat food products, including unpasteurized cheeses. Although the colonization and persistence characteristics of E. coli O157:H7 in the bovine host have been studied intensively, this is not the case for small ruminants. Despite many similarities to the bovine host, the pathobiology of E. coli O157:H7 in small domestic ruminants does appear to differ significantly from that described in cattle. This review aims to critically review the current knowledge regarding colonization and persistence of E. coli O157:H7 in small domestic ruminants, including comparisons with the bovine host where appropriate.

Production and characterization of rabbit polyclonal sera against Shiga toxins Stx1 and Stx2 for detection of Shiga toxin-producing Escherichia coli

STEC has emerged as an important group of enteric pathogens worldwide. In this study, rabbit polyclonal Stx1 and Stx2 antisera were raised and employed in the standardization of immunoassays for STEC detection. Using their respective antisera, the limit of detection of the toxin was 35.0 pg for Stx1 and 5.4 pg for Stx2. By immunoblotting, these antisera recognized both toxin subunits. Cross-reactivity was observed in the A subunit, but only Stx2 antiserum was able to neutralize the cytotoxicity of both toxins in the Vero cell assay. Six stx-harboring E. coli isolates were analyzed for their virulence traits. They belonged to different serotypes, including the O48:H7, described for the first time in Brazil. Only three strains harbored eae, and the e-hly gene and hemolytic activity was detected in five strains. Three isolates showed new stx2 variants (stx(2v-ha) and stx(2vb-hb)). The ELISA assay detected all six isolates, including one VCA-negative isolate, while the immunodot assay failed to detect one isolate, which was VCA-positive. In contrast, the colony-immunoblot assay detected only one VCA-positive isolate. Our results demonstrate that among the immunoassays developed in this study, the immunodot, and particularly the ELISA, appear as perspective for STEC detection in developing countries.

Virulence properties and antimicrobial susceptibility of Shiga toxin-producing Escherichia coli strains isolated from healthy cattle from Paraná State, Brazil

The presence of Shiga toxin-producing Escherichia coli (STEC) strains in feces samples of cattle was determined using the cytotoxicity assay on Vero cells and a screening PCR system to detect stx genes. The STEC isolates were serotyped, tested for antimicrobial susceptibility, and analyzed for virulence genes using multiplex PCR. The verocytotoxin-producing E. coli - reverse passive latex agglutination (VTEC-RPLA) assay was also used to detect Shiga toxin production. The frequency of cattle shedding STEC was 36%. The isolates belonged to 33 different serotypes, of which O10:H42, O98:H41, and O159:H21 had not previously been associated with STEC. The most frequent serotypes were ONT:H7 (10%), O22:H8 (7%), O22:H16 (7%), and ONT:H21 (7%). Most of the strains (96%) were susceptible to all antimicrobial agents tested. Shiga toxin was detected by the VTEC-RPLA assay in most (89%) of the STEC strains. The frequency of virulence markers was as follows: stx1, 10%; stx2, 43%; stx1 plus stx2, 47%; ehxA, 44%; eae, 1%; and saa, 38%. Several strains belong to serotypes associated with human disease, and most of them carried a stx2-type gene, suggesting that they represent a risk to human health. The screening PCR assay showed fewer false-negative results for STEC than the Vero-cell assay and is suitable for laboratory routine.

Detecção de Escherichia coli O157:H7 inoculada experimentalmente em amostras de leite cru por método convencional e PCR multiplex

Padronizou-se um método de reação em cadeia da polimerase (PCR) multiplex para detecção de Escherichia coli O157:H7 e avaliou-se a eficiência da PCR e de um método de cultivo convencional em placas na detecção desse patógeno experimentalmente adicionado em leite estéril e em leite cru com baixa contagem bacteriana total (média de 4,01 x 10³ UFC/ml) e com alta contagem bacteriana (média de 2,10 x 10(6) UFC/ml). Foram padronizadas duas reações de PCR com o uso dos primers: "A" (RfbF; RfbR e FLICh7F/FLICh7R) e "B" (SLT-IF/SLTIR e SLT-IIF/SLT-IIR). A detecção de E. coli O157:H7 (1UFC/ml) a partir do leite estéril e do leite cru com baixa contaminação bacteriana foi possível quando se utilizou o método de contagem em placas e a PCR. A sensibilidade dos dois métodos foi menor quando se testou o leite cru com alta contaminação microbiana, sendo o método convencional mais sensível. Os resultados indicam que a presença de outros microrganismos, em alta quantidade no leite, dificulta a detecção de E. coli O157:H7 pelos métodos utilizados.

Genetic relatedness of a non-motile variant O157 enteropathogenic Escherichia coli (EPEC) strain and E. coli strains belonging to pathogenic related groups

The study was undertaken to determine the clonal relationship and the genetic diversity among Escherichia coli isolates by comparing a non-motile O157 variant with three O157:H7 EHEC isolates and one O55:H7 enteropathogenic E. coli (EPEC) strain. E. coli strains were characterized by sorbitol phenotype, multilocus enzyme electrophoresis, pulsed-field gel electrophoresis, random amplification polymorphic DNA, and the presence of specific virulence genes (stx, E-hly and LEE genes). Sorbitol fermentation was observed in O157:H- (strain 116I), O55:H7 and O157:H7 (strain GC148) serotypes. stx1 or stx2 and E-hly genes were only detected among O157:H7 isolates. LEE typing revealed specific allele distribution: eaegamma, tirgamma, espAgamma, espBgamma associated with EPEC O55:H7 and EHEC O157:H7 strains (B1/1 and EDL 933), eaealpha, tiralpha, espAalpha, espBalpha related to the 116I O157:H- strain and the GC148 strain presented non-typable LEE sequences. Multilocus enzyme profiles revealed two main clusters associated with specific LEE pathotypes. E. coli strains were discriminated by random amplification of polymorphic DNA-polymerase chain reaction and pulsed-field gel electrophoresis methodologies. The molecular approaches used in this study allowed the determination of the genetic relatedness among E. coli strains as well as the detection of lineage specific group markers.

Common epitopes in LPS of different Enterobacteriaceae are associated with an immune response against Escherichia coli O157 in bovine serum samples

Epidemiological studies in both humans and animals conducted in Mexico have shown that the isolation frequency of Escherichia coli O157 : H7 is low. In a previous study, IgG antibodies against E. coli O157, O7 and O116 LPS were found in serum samples from children and adults with no previous history of E. coli O157 : H7 infection. The present study was designed to determine whether a similar immune response against E. coli O157 : H7 and other antigenically related bacteria was present in bovine serum samples. A total of 310 serum samples from different herds in Mexico was analysed by microagglutination assays against different enterobacterial antigens, including E. coli O157. Microagglutination assays were positive against E. coli O7 (55 %), O116 (76 %) and O157 (36 %), Escherichia hermannii (15 %), Salmonella enterica serotype Urbana (14 %) and Salmonella enterica subsp. arizonae (40 %). These results were confirmed using a specific ELISA with purified LPS. A positive reaction was observed against the LPS of E. coli O7 (29 %), O116 (12 %) and O157 (22 %), E. hermannii (4 %), Salmonella Urbana (13 %) and S. enterica subsp. arizonae (12 %). Serum absorption studies of positive serum samples indicated the existence of at least three common epitopes shared by the LPS of E. coli O7, O116 and O157, and two others between E. coli O157 and Salmonella Urbana and S. enterica subsp. arizonae. A bactericidal assay against E. coli O157 : H7 using 31 bovine serum samples was performed, and 22 (71 %) of these serum samples gave positive results. The data demonstrated that bovine serum showed a response against different enterobacteria, including E. coli O157, and that this response could be due to the presence of shared epitopes in the LPS of these organisms.

Prevalence and genetic profiles of Shiga toxin-producing Escherichia coli strains isolated from buffaloes, cattle, and goats in central Vietnam

We investigated the prevalence of Shiga toxin-producing Escherichia coli (STEC) in 568 healthy domestic animals (buffaloes, cattle, and goats) from 98 farms in the central region of Vietnam. The aims of this study were to determine if the prevalence of STEC in South East Asia is similar to that in other parts of the world, to characterize the virulence gene profiles from the recovered STEC and to determine if the recovered STEC belong to serotypes commonly associated with human disease. STEC and intimin-positive strains were recovered from 27% of buffaloes, 23% of cattle, and 38.5% of goats. Seventy percent of buffalo farms, 60% of cattle farms and 100% goat farms were positive for STEC. Of 170 STEC strains, 99 carried both stx1 and stx2 genes, 36 carried the stx2 gene, and 35 carried the stx1 gene. The eae gene was found in six caprine isolates, but not in buffalo or bovine isolates. Among 173 E. coli strains (170 STEC and 3 intimin-positive), 110 carried the ehxA gene, 106 possessed the saa gene. Further characterization of stx subtypes demonstrated that among 134 stx1-containing isolates, 107 belonged to the stx1c subtype and 27 were the stx1 subtype. Of the 132 stx2-containing isolates, 36 were stx2, 34 were stx2c, 43 were stx2d subtype, 3 belonged to stx2g, and 16 strains were stx2d(act). The stx2c variant was dominant in strains isolated from buffalo while the stx2d variant occurred more frequently in caprine isolates. Only 9 (5%) STEC strains contained genes encoding for serotypes O26, O91, O121, O145, and O157 LPS, which are more frequently associated with human infections. The results of this study provide data for understanding of epidemiology of STEC among domestic animals in Vietnam and indicate that buffaloes are also an important reservoir of STEC.

Water buffaloes (Bubalus bubalis) identified as an important reservoir of Shiga toxin-producing Escherichia coli in Brazil

The presence of Shiga toxin-producing Escherichia coli (STEC) in water buffaloes is reported for the first time in South America. The prevalence of STEC ranged from 0 to 64% depending on the farm. STEC isolates exhibiting the genetic profiles stx(1)stx(2)ehxA iha saa and stx(2)ehxA iha saa predominated. Of the 20 distinct serotypes identified, more than 50% corresponded to serotypes associated with human diseases.

Virulence markers and serotypes of Shiga toxin-producing Escherichia coli, isolated from cattle in Rio Grande do Sul, Brazil

AIMS

To determine the prevalence of Shiga toxin-producing Escherichia coli (STEC) and serotypes and virulence markers of the STEC isolates from beef and dairy cattle in Rio Grande do Sul, Brazil.

METHODS AND RESULTS

Faecal samples from beef cattle were collected at slaughterhouses. The isolates were submitted to colony hybridization assay with specific DNA probes for stx1, stx2 and eae genes, and serotyped for the identification of O and H antigens. Thirty-nine per cent of beef cattle surveyed harboured at least one STEC strain. Among the distinct serotypes identified, 10 were shared by both beef and dairy cattle. Most of the strains isolated harboured stx2. Genotypic and phenotypic profiles allowed the identification of 34 and 31 STEC strains, isolated from beef and dairy cattle, respectively. Serotypes O10:H14, O15:H21, O96:H21, O119:H4, O124:H11, O128:H21, O137:H-, O141:H19, O159:H42, O160:H2 and O177:H11, identified in this study, have not been previously reported as STEC isolated from cattle.

CONCLUSIONS

Cattle are an important reservoir of STEC strains associated with human diseases in South America.

SIGNIFICANCE AND IMPACT OF THE STUDY

Determining the prevalence, genotypic profile and serotypes of STEC strains isolated from cattle enables the prediction of possible risk for public health.

Serotypes, virulence genes, and intimin types of Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) isolated from calves in São Paulo, Brazil

Shiga toxin-producing Escherichia coli (STEC), is the most important recently emerged group of foodborne pathogens. Ruminants, especially cattle, have been implicated as a principal reservoir of STEC, undercooked ground beef and raw milk being the major vehicles of foodborne outbreaks. Enteropathogenic E. coli (EPEC) strains are defined as eae-harboring diarrheagenic E. coli that possess the ability to form A/E lesions on intestinal cells and that do not possess Shiga toxin genes. In order to determine the occurrence, serotypes and virulence markers of STEC and EPEC strains, 546 fecal samples from 264 diarrheic calves and 282 healthy calves in beef farms in São Paulo, Brazil, were screened by PCR. STEC and EPEC were isolated in 10% and 2.7% of the 546 animals, respectively. Although IMS test was used, the STEC serotype O157:H7 was not detected. The most frequent serotypes among STEC strains were O7:H10, O22:H16, O111:H(-), O119:H(-) and O174:H21, whereas O26:H11, O123:H11 and O177:H11 were the most prevalent among EPEC strains. In this study, serotypes not previously reported were found among STEC strains: O7:H7, O7:H10, O48:H7, O111:H19, O123:H2, O132:H51, O173:H(-), and O175:H49. The eae gene was detected in 25% of the STEC and 100% of EPEC strains. The intimin type theta/gamma2 was the most frequent among STEC, whereas the intimin beta1 was the most frequent intimin type among EPEC strains. To our knowledge, this is the first report of the occurrence of the new intimin muB in one strain of animal origin. This new intimin was detected in one atypical EPEC strain of serotype O123:H? isolated from diarrheic cattle. The enterohemolysin (ehxA) was detected in 51% of the STEC and 80% of the EPEC strains, whereas STEC autoagglutinating adhesin (saa) virulence gene was detected only in those STEC strains negative for eae gene. All 15 bovine EPEC strains isolated in this study were negative for both eaf and bfp genes. Our data shows that in Brazil cattle are not only a reservoir of STEC and atypical EPEC, but also a potential source of infection in humans, since the important STEC serotypes previously described and associated with severe diseases in humans, such as O111:H(-), O113:H21, O118:H16, and O174:H21 were isolated.

Phenotypic and genotypic traits of Shiga toxin-producingEscherichia colistrains isolated from beef cattle from Paraná State, southern Brazil

AIMS

To investigate the prevalence and characteristics of Shiga toxin-producing Escherichia coli (STEC) in cattle from Paraná State, southern Brazil.

METHODS AND RESULTS

One hundred and seven faeces cattle samples were cultured on Sorbitol-MacConkey agar. Escherichia coli colonies were tested for production of Shiga toxin using Vero-cell assay. A high prevalence (57%) of STEC was found. Sixty-four STEC were serotyped and examined for the presence of stx(1), stx(2), eae, ehxA and saa genes and stx(2) variants. The isolates belonged to 31 different serotypes, of which three (O152:H8, O175:H21 and O176:H18) had not previously been associated with STEC. A high prevalence of stx(2)-type genes was found (62 strains, 97%). Variant forms found were stx(2), stx(2c), stx(2vhb), stx(2vO111v/OX393) and a form nonclassifiable by PCR-RFLP. The commonest genotypes were stx(2)ehxA saa and stx(1)stx(2)ehxA saa.

CONCLUSIONS

A high frequency of STEC was observed. Several strains belong to serotypes previously associated with human disease and carry stx(2) and other virulence factors, thus potentially representing a risk to human health.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study of STEC in Paraná State, and its findings emphasize the need for proper cattle handling to prevent human contamination.