Serotypes and virulence markers of Shiga toxin-producing Escherichia coli (STEC) isolated from dairy cattle in São Paulo 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.

Characterization of Shiga Toxin-producing Escherichia coli Isolated from Cattle Around Ulaanbaatar City, Mongolia

Shiga toxin-producing Escherichia coli (STEC) are associated with severe infections including hemorrhagic colitis and hemolytic uremic syndrome in humans. Ruminants are known as reservoirs of STEC; however, no data are available on STEC in ruminants in Mongolia, where more than 5 million cattle and 25 million sheep are raised. To disclose the existence and characteristics of STEC in Mongolia, in this study, we isolated and characterized STEC from cattle in Mongolia. We collected 350 rectal swabs of cattle from 30 farms near Ulaanbaatar city and isolated 45 STEC from 21 farms. Rectal swabs were precultured with modified Escherichia coli broth and then inoculated to Cefixime-Tellurite Sorbitol MacConkey agar plate and/or CHROMagar STEC agar plate for the isolation of STEC. The isolation ratios in each farm were from 0% to 40%. Multiplex PCR for the estimation of O- and H-serotypes identified 12 O-genotypes (Og-types) and 11 H-genotypes (Hg-types) from 45 isolates; however, Og-types of 19 isolates could not be determined. Stx gene subtyping by PCR identified 2 stx1 subtypes (1a and 1c) and 4 stx2 subtypes (2a, 2c, 2d, and 2g). Forty-five isolates were divided into 21 different groups based on the Og- and Hg-types, stx gene subtypes and the existence of virulence factors, ehxA, eae, and saa, which includes several major serotypes associated with human illness such as O26:H11 and O157:H7. The most dominant isolate, OgUT:H19 [stx1a (+), stx2a (+), ehxA (+) and saa (+)], was isolated from eight farms. This is the first report on the characterization of STEC in cattle in Mongolia, and the results suggest the importance of further monitoring of STEC contamination in the food chains as well as STEC infection in humans.

Pathogenomes and variations in Shiga toxin production among geographically distinct clones of Escherichia coli O113:H21

Infections with globally disseminated Shiga toxin-producing Escherichia coli (STEC) of the O113:H21 serotype can progress to severe clinical complications, such as hemolytic uremic syndrome (HUS). Two phylogeographically distinct clonal complexes have been established by multi locus sequence typing (MLST). Infections with ST-820 isolates circulating exclusively in Australia have caused severe human disease, such as HUS. Conversely, ST-223 isolates prevalent in the US and outside Australia seem to rarely cause severe human disease but are frequent contaminants. Following a genomic epidemiology approach, we wanted to gain insights into the underlying cause for this disparity. We examined the plasticity in the genome make-up and Shiga toxin production in a collection of 20 ST-820 and ST-223 strains isolated from produce, the bovine reservoir, and clinical cases. STEC are notorious for assembly into fragmented draft sequences when using short-read sequencing technologies due to the extensive and partly homologous phage complement. The application of long-read technology (LRT) sequencing yielded closed reference chromosomes and plasmids for two representative ST-820 and ST-223 strains. The established high-resolution framework, based on whole genome alignments, single nucleotide polymorphism (SNP)-typing and MLST, includes the chromosomes and plasmids of other publicly available O113:H21 sequences and allowed us to refine the phylogeographical boundaries of ST-820 and ST-223 complex isolates and to further identify a historic non-shigatoxigenic strain from Mexico as a quasi-intermediate. Plasmid comparison revealed strong correlations between the strains' featured pO113 plasmid genotypes and chromosomally inferred ST, which suggests coevolution of the chromosome and virulence plasmids. Our pathogenicity assessment revealed statistically significant differences in the Stx_2a-production capabilities of ST-820 as compared to ST-223 strains under RecA-induced Stx phage mobilization, a condition that mimics Stx-phage induction. These observations suggest that ST-820 strains may confer an increased pathogenic potential in line with the strain-associated epidemiological metadata. Still, some of the tested ST-223 cultures sourced from contaminated produce or the bovine reservoir also produced Stx at levels comparable to those of ST-820 isolates, which calls for awareness and for continued surveillance of this lineage.

Antimicrobial susceptibility of Salmonella spp and Staphylococcus aureus isolated from beef sold in Campo Grande, Mato Grosso do Sul, Brazil

Abstract Hygiene failures in meat can be identified based on the evaluation of pathogenic microorganisms, which compromise the microbiological quality of food and can transmit food-borne diseases. The aim of the present study was to evaluate the hygienic quality of beef sold at supermarkets, butcher shops and public markets in the city of Campo Grande, state of Mato Grosso do Sul, Brazil, through the phenotypic and genotypic characterization of Salmonella spp. and Shiga toxin-producing Escherichia coli (STEC) as well as the investigation and quantification of Staphylococcus aureus. Seventy-one samples of beef from 17 commercial establishments were evaluated. Isolates were tested for antimicrobial susceptibility using the disk diffusion method recommended by the Clinical & Laboratory Standards Institute. Salmonella was found in 7.04% of the samples and 70.0% of the isolates were sensitive to the antimicrobials tested. A total of 25.35% of the samples were positive for Staphylococcus aureus, with counts ranging from 1.0 x 102 to 4.3 x 104 CFU/g; these isolates exhibited resistance to penicillin (87.5%), tetracycline (18.75%) and chloramphenicol (6.25%). None of the samples was positive for STEC. The detection of these pathogens in food poses a danger to public health, mainly due to the presence of antimicrobial-resistant isolates. These findings underscore the need for good hygiene and manufacturing practices at retail establishments.

Characterisation of Early Positive mcr-1 Resistance Gene and Plasmidome in Escherichia coli Pathogenic Strains Associated with Variable Phylogroups under Colistin Selection

An antibiotic susceptibility monitoring programme was conducted from 2004 to 2010, resulting in a collection of 143 Escherichia coli cultured from bovine faecal samples (diarrhoea) and milk-aliquots (mastitis). The isolates were subjected to whole-genome sequencing and were distributed in phylogroups A, B1, B2, C, D, E, and G with no correlation for particular genotypes with pathotypes. In fact, the population structure showed that the strains belonging to the different phylogroups matched broadly to ST complexes; however, the isolates are randomly associated with the diseases, highlighting the necessity to investigate the virulence factors more accurately in order to identify the mechanisms by which they cause disease. The antimicrobial resistance was assessed phenotypically, confirming the genomic prediction on three isolates that were resistant to colistin, although one isolate was positive for the presence of the gene mcr-1 but susceptible to colistin. To further characterise the genomic context, the four strains were sequenced by using a single-molecule long read approach. Genetic analyses indicated that these four isolates harboured complex and diverse plasmids encoding not only antibiotic resistant genes (including mcr-1 and bla) but also virulence genes (siderophore, ColV, T4SS). A detailed description of the plasmids of these four E. coli strains, which are linked to bovine mastitis and diarrhoea, is presented for the first time along with the characterisation of the predicted antibiotic resistance genes. The study highlighted the diversity of incompatibility types encoding complex antibiotic resistance elements such as Tn6330, ISEcp1, Tn6029, and IS5075. The mcr-1 resistance determinant was identified in IncHI2 plasmids pCFS3273-1 and pCFS3292-1, thus providing some of the earliest examples of mcr-1 reported in Europe, and these sequences may be a representative of the early mcr-1 plasmidome characterisation in the EU/EEA.

Molecular surveillance of shiga toxigenic Escherichia coli in selected beef abattoirs in Osun State Nigeria

Shiga toxigenic strains of E. coli (STEC) known to be etiological agents for diarrhea were screened for their incidence/occurrence in selected abattoirs sources in Osogbo metropolis of Osun State, Nigeria using a randomized block design. Samples were plated directly on selective and differential media and E. coli isolates. Multiplex PCR analysis was used to screen for the presence of specific virulence factors. These were confirmed serologically as non-O157 STEC using latex agglutination serotyping kit. Sequence analysis of PCR products was performed on a representative isolate showing the highest combination of virulence genes using the 16S gene for identification purposes only. Results showed that the average cfu/cm2 was significantly lower in the samples collected at Sekona-2 slaughter slab compared with those collected at Al-maleek batch abattoir and Sekona-1 slaughter slab in ascending order at P = 0.03. Moreover, the average cfu/cm2 E. coli in samples collected from butchering knife was significantly lower when compared with that of the workers' hand (P = 0.047) and slaughtering floor (P = 0.047) but not with the slaughter table (P = 0.98) and effluent water from the abattoir house (P = 0.39). These data suggest that the abattoir type may not be as important in the prevalence and spread of STEC as the hygiene practices of the workers. Sequence analysis of a representative isolate showed 100% coverage and 96.46% percentage identity with Escherichia coli O113:H21 (GenBank Accession number: CP031892.1) strain from Canada. This sequence was subsequently submitted to GenBank with accession number MW463885. From evolutionary analyses, the strain from Nigeria, sequenced in this study, is evolutionarily distant when compared with the publicly available sequences from Nigeria. Although no case of E. coli O157 was found within the study area, percent occurrence of non-O157 STEC as high as 46.3% at some of the sampled sites is worrisome and requires regulatory interventions in ensuring hygienic practices at the abattoirs within the study area.

Multiplex PCR Assays for the Detection of One Hundred and Thirty Seven Serogroups of Shiga Toxin-Producing Escherichia coli Associated With Cattle

Escherichia coli carrying prophage with genes that encode for Shiga toxins are categorized as Shiga toxin-producing E. coli (STEC) pathotype. Illnesses caused by STEC in humans, which are often foodborne, range from mild to bloody diarrhea with life-threatening complications of renal failure and hemolytic uremic syndrome and even death, particularly in children. As many as 158 of the total 187 serogroups of E. coli are known to carry Shiga toxin genes, which makes STEC a major pathotype of E. coli. Seven STEC serogroups, called top-7, which include O26, O45, O103, O111, O121, O145, and O157, are responsible for the majority of the STEC-associated human illnesses. The STEC serogroups, other than the top-7, called “non-top-7” have also been associated with human illnesses, more often as sporadic infections. Ruminants, particularly cattle, are principal reservoirs of STEC and harbor the organisms in the hindgut and shed in the feces, which serves as a major source of food and water contaminations. A number of studies have reported on the fecal prevalence of top-7 STEC in cattle feces. However, there is paucity of data on the prevalence of non-top-7 STEC serogroups in cattle feces, generally because of lack of validated detection methods. The objective of our study was to develop and validate 14 sets of multiplex PCR (mPCR) assays targeting serogroup-specific genes to detect 137 non-top-7 STEC serogroups previously reported to be present in cattle feces. Each assay included 7–12 serogroups and primers were designed to amplify the target genes with distinct amplicon sizes for each serogroup that can be readily identified within each assay. The assays were validated with 460 strains of known serogroups. The multiplex PCR assays designed in our study can be readily adapted by most laboratories for rapid identification of strains belonging to the non-top-7 STEC serogroups associated with cattle.

Interactions of Shiga toxin-producing Escherichia coli with leafy green vegetables

Shiga toxin-producing Escherichia coli (STEC) are important foodborne pathogens responsible for a wide spectrum of diseases including diarrhea, bloody diarrhea, and hemolytic uremic syndrome (HUS). A considerable number of outbreaks and sporadic cases of HUS have been associated with ingestion of fresh ready-to-eat products. Maintenance and persistence of STEC in the environment and foods can be related to its ability to form biofilm. A non-O157 STEC strain isolated from bovine feces was distinguished by its great ability to form biofilm in abiotic surfaces. In the present study, we aimed to investigate the ability of this strain to adhere to rocket leaves (Eruca sativa). Adherence assays were carried out for 3 h at 28 °C and analyzed by scanning electron microscopy. The non-O157 STEC strain adhered to leaf surface and inside the stomata forming several bacterial aggregates. The number of adherent bacteria per square millimeter of leaf was eightfold higher compared with an O157 STEC strain. Deletion of the STEC autotransporter protein contributing to biofilm (Sab) reduced the adherence ability of the non-O157 strain in almost 50%, and deletion of antigen 43 (Ag43) almost abolished this interaction. Very few bacteria were seen on the leaf surface, and these differences were statistically significant, suggesting the role of both proteins and especially Ag43 in the interaction of the non-O157 STEC strain with leaves. The risk posed by non-O157 STEC adherence to leaves on fresh produce contamination should not be neglected, and measures that effectively control adherence should be included in strategies to control non-O157 STEC.

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.

Comment on "Shiga-Toxin Producing Escherichia coli in Brazil: A Systematic Review. Microorganisms 2019, 7, 137"

A recent article by Castro et al. describes a systematic review of Shiga-toxin producingEscherichia coli (STEC) in Brazil. [...].

Shiga-Toxin Producing Escherichia Coli in Brazil: A Systematic Review

Shiga-toxin producing E. coli (STEC) can cause serious illnesses, including hemorrhagic colitis and hemolytic uremic syndrome. This is the first systematic review of STEC in Brazil, and will report the main serogroups detected in animals, food products and foodborne diseases. Data were obtained from online databases accessed in January 2019. Papers were selected from each database using the Mesh term entries. Although no human disease outbreaks in Brazil related to STEC has been reported, the presence of several serogroups such as O157 and O111 has been verified in animals, food, and humans. Moreover, other serogroups monitored by international federal agencies and involved in outbreak cases worldwide were detected, and other unusual strains were involved in some isolated individual cases of foodborne disease, such as serotype O118:H16 and serogroup O165. The epidemiological data presented herein indicates the presence of several pathogenic serogroups, including O157:H7, O26, O103, and O111, which have been linked to disease outbreaks worldwide. As available data are concentrated in the Sao Paulo state and almost completely lacking in outlying regions, epidemiological monitoring in Brazil for STEC needs to be expanded and food safety standards for this pathogen should be aligned to that of the food safety standards of international bodies.

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.

Characterization of Diarrheagenic Strains of Escherichia coli Isolated From Cattle Raised in Three Regions of Mexico

Intestinal infections represent an important public health concern worldwide. Escherichia coli is one of the main bacterial agents involved in the pathogenesis of different diseases. In 2011, an outbreak of hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) in Germany was related to a non-O157 STEC strain of O104:H4 serotype. The difficulty in identifying the origin of the bacteria related to the outbreak showed the importance of having epidemiological information from different parts of the world. The aim of this study was to perform a retrospective analysis to determine if E. coli strains isolated from cattle from different locations in Mexico have similar characteristics to those isolated in other countries. Samples obtained in different years from 252 cows belonging to 5 herds were analyzed. A total of 1,260 colonies were selected from the 252 samples, 841 (67%) of which corresponded to E. coli and 419 (33%) to other enterobacteria. In total, 78% (656) of the E. coli strains could be serotyped, of which 393 (59.9%) belonged to 5 diarrheagenic (DEC) pathotypes. Serotyping showed STEC (40.7%) and ETEC (26.7%) strains were more common. PCR assays were used to determine the presence of STEC (eae, stx1, stx2, and ehxA) and EAEC (aatA, aggR, and aapA) genes, and phylogenetic groups. The results showed that 70 strains belonging to 23 serogroups were stx1 and stx2 positive, while 13 strains from the O9 serogroup were ehxA, aggR, and eae positive. Phylogenetic analysis showed 58 (82.9%) strains belonged to A and B1 commensal phylogroups and 12 (17.1%) to B2, D and E virulent phylogroups. An assay to evaluate cross-antigenic reactivity in the serum of cattle between K9 capsular antigen and O104 LPS by ELISA showed similar responses against both antigens (p > 0.05). The antimicrobial sensitivity assay of the strains showed resistance to AM, CEP, CXM, TE, SXT, cephalosporins and fluoroquinolones. The results show that cattle are carriers and potential transmitters of STEC and ETEC strains containing virulence genes. Epidemiological retrospective studies in different countries are of great help for identifying virulent bacterial strains with the potential to cause outbreaks that may have epidemiological impact in susceptible countries.

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.

Toxins of Locus of Enterocyte Effacement-Negative Shiga Toxin-Producing Escherichia coli

Studies on Shiga toxin-producing Escherichia coli (STEC) typically examine and classify the virulence gene profiles based on genomic analyses. Among the screened strains, a subgroup of STEC which lacks the locus of enterocyte effacement (LEE) has frequently been identified. This raises the question about the level of pathogenicity of such strains. This review focuses on the advantages and disadvantages of the standard screening procedures in virulence profiling and summarizes the current knowledge concerning the function and regulation of toxins encoded by LEE-negative STEC. Although LEE-negative STEC usually come across as food isolates, which rarely cause infections in humans, some serotypes have been implicated in human diseases. In particular, the LEE-negative E. coli O104:H7 German outbreak strain from 2011 and the Australian O113:H21 strain isolated from a HUS patient attracted attention. Moreover, the LEE-negative STEC O113:H21 strain TS18/08 that was isolated from minced meat is remarkable in that it not only encodes multiple toxins, but in fact expresses three different toxins simultaneously. Their characterization contributes to understanding the virulence of the LEE-negative STEC.

Virulence genes, Shiga toxin subtypes, major O-serogroups, and phylogenetic background of Shiga toxin-producing Escherichia coli strains isolated from cattle in Iran

The aim of this study was to investigate the virulence potential of the isolated bovine STEC for humans in Iran. In this study a collection of STEC strains (n = 50) had been provided via four stages, including sampling from feces of cattle, E. coli isolation, molecular screening of Shiga toxin (stx) genes, and saving the STEC strains from various geographical areas in Iran. The STEC isolates were subjected to stx-subtyping, O-serogrouping, and phylo-grouping by conventional polymerase chain reaction (PCR). Occurrence of stx1 (52%) and stx2 (64%) was not significantly different (p = 0.1), and 16% of isolates carried both stx1 and stx2, simultaneously. In addition, 36% and 80% of the isolates were positive for eae and ehxA, respectively. Molecular subtyping showed that stx1a (52%), stx2a (44%), stx2c (44%), and stx2d (30%) were the most prevalent subtypes; two combinations stx2a/stx2c and stx2c/stx2d coexisted in 18% and 10% of STEC strains, respectively. Three important non-O157 serogroups, including O113 (20%), O26 (12%), and O111 (10%), were predominant, and none of the isolates belonged to O157. Importantly, one O26 isolate carried stx1, stx2, eae and ehxA and revealed highly virulent stx subtypes. Moreover, all the 21 serogrouped strains belonged to the B1 phylo-type. Our study highlights the significance of non-O157 STEC strains carrying highly pathogenic virulence genes in cattle population as the source of this pathogen in Iran. Since non-O157 STEC strains are not routinely tried in most diagnostic laboratories, majority of the STEC-associated human infections appear to be overlooked in the clinical settings.

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.

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.

In silico serotyping of E. coli from short read data identifies limited novel O-loci but extensive diversity of O:H serotype combinations within and between pathogenic lineages

The lipopolysaccharide (O) and flagellar (H) surface antigens of Escherichia coli are targets for serotyping that have traditionally been used to identify pathogenic lineages. These surface antigens are important for the survival of E. coli within mammalian hosts. However, traditional serotyping has several limitations, and public health reference laboratories are increasingly moving towards whole genome sequencing (WGS) to characterize bacterial isolates. Here we present a method to rapidly and accurately serotype E. coli isolates from raw, short read WGS data. Our approach bypasses the need for de novo genome assembly by directly screening WGS reads against a curated database of alleles linked to known and novel E. coli O-groups and H-types (the EcOH database) using the software package srst2. We validated the approach by comparing in silico results for 197 enteropathogenic E. coli isolates with those obtained by serological phenotyping in an independent laboratory. We then demonstrated the utility of our method to characterize isolates in public health and clinical settings, and to explore the genetic diversity of >1500 E. coli genomes from multiple sources. Importantly, we showed that transfer of O- and H-antigen loci between E. coli chromosomal backbones is common, with little evidence of constraints by host or pathotype, suggesting that E. coli ‘strain space’ may be virtually unlimited, even within specific pathotypes. Our findings show that serotyping is most useful when used in combination with strain genotyping to characterize microevolution events within an inferred population structure.

Identification of Extended-Spectrum β-Lactamases Escherichia coli Strains Isolated from Market Garden Products and Irrigation Water in Benin

The present study aimed at biochemical and molecular characterization of Escherichia coli strains isolated from horticultural products and irrigation water of Cotonou. The samples were collected from 12 market gardeners of 4 different sites. Rapid' E. coli medium was used for identification of E. coli strains and the antimicrobial susceptibility was performed by the agar disk diffusion method. The β-lactamases production was sought by the liquid acidimetric method. The genes coding for β-lactamases and toxins were identified by PCR method. The results revealed that about 34.95% of the analyzed samples were contaminated by E. coli. Cabbages were the most contaminated by E. coli (28.26%) in dry season. All isolated strains were resistant to amoxicillin. The penicillinase producing E. coli carried blaTEM (67.50%), blaSHV (10%), and blaCTX-M (22.50%) genes. The study revealed that the resistance genes such as SLTI (35.71%), SLTII (35.71%), ETEC (7.15%), and VTEC (21.43%) were carried. Openly to the found results and considering the importance of horticultural products in Beninese food habits, it is important to put several strategies aiming at a sanitary security by surveillance and sensitization of all the actors on the risks of some practices.

Characterization of Shiga Toxigenic Escherichia coli O157 and Non-O157 Isolates from Ruminant Feces in Malaysia

Shiga toxigenic Escherichia coli (STEC) O157 and several other serogroups of non-O157 STEC are causative agents of severe disease in humans world-wide. The present study was conducted to characterize STEC O157 and non-O157 serogroups O26, O103, O111, O121, O45, and O145 in ruminants in Malaysia. A total of 136 ruminant feces samples were collected from 6 different farms in Peninsular Malaysia. Immunomagnetic beads were used to isolate E. coli O157 and non-O157 serogroups, while PCR was used for the detection and subtyping of STEC isolates. STEC O157:H7 was isolated from 6 (4%) feces samples and all isolates obtained carried stx 2c, eaeA-γ1, and ehxA. Non-O157 STEC was isolated from 2 (1.5%) feces samples with one isolate carrying stx 1a, stx 2a, stx 2c, and ehxA and the other carrying stx 1a alone. The presence of STEC O157 and non-O157 in a small percentage of ruminants in this study together with their virulence characteristics suggests that they may have limited impact on public health.

Dynamics of Escherichia coli Virulence Factors in Dairy Herds and Farm Environments in a Longitudinal Study in the United States

Pathogenic Escherichia coli or its associated virulence factors have been frequently detected in dairy cow manure, milk, and dairy farm environments. However, it is unclear what the long-term dynamics of E. coli virulence factors are and which farm compartments act as reservoirs. This study assessed the occurrence and dynamics of four E. coli virulence factors (eae, stx1, stx2, and the gamma allele of the tir gene [γ-tir]) on three U.S. dairy farms. Fecal, manure, water, feed, milk, and milk filter samples were collected from 2004 to 2012. Virulence factors were measured by postenrichment quantitative PCR (qPCR). All factors were detected in most compartments on all farms. Fecal and manure samples showed the highest prevalence, up to 53% for stx and 21% for γ-tir in fecal samples and up to 84% for stx and 44% for γ-tir in manure. Prevalence was low in milk (up to 1.9% for stx and 0.7% for γ-tir). However, 35% of milk filters were positive for stx and 20% were positive for γ-tir. All factors were detected in feed and water. Factor prevalence and levels, expressed as qPCR cycle threshold categories, fluctuated significantly over time, with no clear seasonal signal independent from year-to-year variability. Levels were correlated between fecal and manure samples, and in some cases autocorrelated, but not between manure and milk filters. Shiga toxins were nearly ubiquitous, and 10 to 18% of the lactating cows were potential shedders of E. coli O157 at least once during their time in the herds. E. coli virulence factors appear to persist in many areas of the farms and therefore contribute to transmission dynamics.

Shiga-toxin genes and genetic diversity of Escherichia coli isolated from pasteurized cow milk in Brazil

This study evaluated the genetic similarity and prevalence of the stx1, stx2, eae, and ehxA genes in Escherichia coli isolated from pasteurized cow milk. Eighty-seven E. coli isolates from pasteurized cow milk from 22 dairies located in northwestern Paraná state, Brazil, were analyzed. Genetic similarity was evaluated using enterobacterial repetitive intergenic consensus sequence polymerase chain reaction (ERIC-PCR) and repetitive extragenic palindromic sequence PCR (REP-PCR). E. coli isolates were also analyzed by PCR to investigate the presence of the stx1, stx2, eae, and ehxA genes. ERIC-PCR and REP-PCR clustered 87 bacterial isolates in 76 and 81 genomic profiles, respectively. Both techniques revealed high genetic diversity among the E. coli isolates, confirming the possibility of their use in epidemiological studies. The stx1, stx2, eae, and ehxA virulence genes were not detected in E. coli isolates, indicating a low prevalence of Shiga toxin-producing E. coli in milk produced in the region studied.

PRACTICAL APPLICATION

Knowledge about the presence of diarrheagenic Escherichia coli in pasteurized milk is important developing and implementing control measures in milk and dairy production.

Characterization of buffalo interleukin 8 (IL-8) and its expression in endometritis

River buffalo (Bubalus bubalis bubalis) with a population over 135 million heads is an important livestock. Interleukin 8 (IL-8) is a member of the chemokine family and is an important chemoattractant for neutrophils associated with a wide variety of inflammatory diseases such as endometritis. Tissue samples from the mammary gland, uterus and ovary were obtained from river buffalo (Mediterranean type) with and without endometritis. Bacteriological examination showed the presence of both gram positive and negative in all buffalo with endometritis. RNA extraction and complementary DNA (cDNA) synthesis were conducted from all tissues. Specific primer for IL8 full coding regions was designed using known cDNA sequences of Bubalus bubalis, Genbank accession number AY952930.1. IL-8 gene expression was investigated in buffalo tissues. Expression of IL-8 in buffalo with endometritis was found to increase significantly over buffalo without endometritis only in the uterus (P = 0.0159). PCR products from uterus tissues (target organs) of buffalo with and without endometritis, were purified and sequenced. No polymorphic sites were detected in the investigated samples. IL-8 cDNA nucleotide sequences of buffalo with and without endometritis were 100% identical (accession number JX413057). Buffalo IL8 cDNAs were compared with corresponding sequences of member of subfamily Bovinae (buffalo and cattle) and subfamily Caprinae (sheep and goat). IL-8 species specific differences were identified.

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.

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.

Genetic diversity and virulence potential of shiga toxin-producing Escherichia coli O113:H21 strains isolated from clinical, environmental, and food sources

Shiga toxin-producing Escherichia coli strains of serotype O113:H21 have caused severe human diseases, but they are unusual in that they do not produce adherence factors coded by the locus of enterocyte effacement. Here, a PCR microarray was used to characterize 65 O113:H21 strains isolated from the environment, food, and clinical infections from various countries. In comparison to the pathogenic strains that were implicated in hemolytic-uremic syndrome in Australia, there were no clear differences between the pathogens and the environmental strains with respect to the 41 genetic markers tested. Furthermore, all of the strains carried only Shiga toxin subtypes associated with human infections, suggesting that the environmental strains have the potential to cause disease. Most of the O113:H21 strains were closely related and belonged in the same clonal group (ST-223), but CRISPR analysis showed a great degree of genetic diversity among the O113:H21 strains.

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.

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.

Shiga toxin-producing Escherichia coli in Central Greece: prevalence and virulence genes of O157:H7 and non-O157 in animal feces, vegetables, and humans

In Greece, Shiga toxin-producing Escherichia coli (STEC) have only been sporadically reported. The objective of this study was to estimate the prevalence of STEC and Escherichia coli O157:H7 in farm animals, vegetables, and humans in Greece. A total number of 1,010 fecal samples were collected from farm animals (sheep, goats, cattle, chickens, pigs), 667 diarrheal samples from humans, and 60 from vegetables, which were cultured in specific media for STEC isolates. Enzyme-linked immunosorbent assay (ELISA) was used to detect toxin-producing colonies, which, subsequently, were subjected to a multiplex polymerase chain reaction (PCR) for stx1, stx2, eae, rfbE O157, and fliC h7 genes. Eighty isolates (7.9 %) from animal samples were found to produce Shiga toxin by ELISA, while by PCR, O157 STEC isolates were detected from 8 (0.8 %) samples and non-O157 STEC isolates from 43 (4.2 %) samples. STEC isolates were recovered mainly from sheep and goats, rarely from cattle, and not from pigs and chickens, suggesting that small ruminants constitute a potential risk for human infections. However, only three human specimens (0.4 %) were positive for the detection of Shiga toxins and all were PCR-negative. Similarly, all 60 vegetable samples were negative for toxin production and for toxin genes, but three samples (two roman rockets and one spinach) were positive by PCR for rfbE O157 and fliC h7 genes. These findings indicate that sheep, goats, cattle, and leafy vegetables can be a reservoir of STEC and Escherichia coli O157:H7 isolates in Greece, which are still rarely detected among humans.

Incidence of Shiga toxin-producing Escherichia coli serogroups in ruminant's meat

To assess the presences of Escherichia coli, its serogroups, virulence factors and antibiotic resistance properties in ruminant's meat, a total of 820 raw meat samples were collected and then evaluated using culture, PCR and disk diffusion methods. Totally, 238 (29.02%) samples were positive for presence of Escherichia coli. All of the isolates had more than one virulence gene including Stx1, Stx2, eaeA and ehly. All investigated serogroups were found in beef and sheep and all except O145, O121 and O128 were found in goat. The O91, O113, O111, O103, O26 and O157 serogroups were found in camel. Totally, aadA1-blaSHV combination was the most predominant antibiotic resistance gene. The highest resistance of STEC strains was seen against penicillin while resistance to nitrofurantoin and ciprofloxacin was minimal. These findings showed that health care and meat inspection should be reconsidered in Iranian slaughterhouses and butchers.

[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.

Quantification of bacterial indicators and zoonotic pathogens in dairy wastewater ponds

Zoonotic pathogens in land-applied dairy wastewaters are a potential health risk. The occurrence and abundance of 10 pathogens and 3 fecal indicators were determined by quantitative real-time PCR (qPCR) in samples from 30 dairy wastewaters from southern Idaho. Samples tested positive for Campylobacter jejuni, stx(1)- and eaeA-positive Escherichia coli, Listeria monocytogenes, Mycobacterium avium subsp. paratuberculosis, and Salmonella enterica, with mean recoveries of genomic DNA corresponding to 10(2) to 10(4) cells ml(-1) wastewater. The most predominant organisms were C. jejuni and M. avium, being detected in samples from up to 21 and 29 of 30 wastewater ponds, respectively. The qPCR detection limits for the putative pathogens in the wastewaters ranged from 16 cells ml(-1) for M. avium to 1,689 oocysts ml(-1) for Cryptosporidium. Cryptosporidium and Giardia spp., Yersinia pseudotuberculosis, and pathogenic Leptospira spp. were not detected by qPCR.

Caracterização molecular e fenotípica de estirpes de Escherichia coli produtoras de shiga-toxina (STEC) não-O157 de fezes e carcaças bovinas

Foram coletados 100 suabes retais e 100 suabes de carcaças bovinas em matadouros do estado de São Paulo, e um total de 326 estirpes de E. coli foram identificadas, sendo 163 de amostras retais e 163 de amostras de carcaça. Todos os isolados submetidos à PCR para detecção dos genes das toxinas Stx1 e Stx2 foram identificados como não-O157 e fenotipados pelo teste da citotoxicidade em células Vero. Das 26 estirpes que apresentaram apenas o gene stx1, das 56 que apresentaram apenas o gene stx2 e das 30 estirpes que apresentaram ambos os genes, 17 (65,4%), 42 (75%) e 22 (73,3%), respectivamente, foram positivas ao teste de citotoxicidade. Não houve diferença estatística entre os três perfis genéticos e na positividade ao teste de citotoxicidade. Os resultados mostram a alta frequência de expressão dos fatores de virulência das STEC de bovinos.

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.

Virulence characterization of Shiga-toxigenic Escherichia coli isolates from wholesale produce

The 13 Shiga-toxigenic Escherichia coli (STEC) strains isolated from wholesale spinach and lettuce consisted mostly of serotypes that have not been implicated in illness. Among these strains, however, were two O113:H21 that carried virulence genes common to this pathogenic serotype (stx(2), ehxA, saa, and subAB), suggesting that their presence in ready-to-eat produce may be of health concern.

Molecular typing of antimicrobial-resistant Shiga-toxin-producing Escherichia coli strains (STEC) in Brazil

Antimicrobial resistance patterns and molecular characteristics were determined in thirty-two Shiga-toxin-producing Escherichia coli (STEC) strains previously identified in São Paulo State associated with human infections (n = 21) and in cattle feces (n = 11). The highest resistance rates were identified for tetracycline (100%), streptomycin (78%) and trimethoprim-sulfamethoxazole (56%). Eleven STEC strains showed resistance to ampicillin and carried bla(TEM) that was confirmed as bla(TEM-1) in one representative isolate. The class 1 integrase gene (intI1) was detected in seven (22%) strains, and most of them belonged to the O111:H8 serotype. The class 1 integron was located on plasmids in five of the seven STEC strains, and conjugation assays confirmed the plasmid support of those resistant determinants. STEC strains were genetically classified into the B1 group, and PFGE analysis showed that most of the strains in each serogroup were grouped into the same cluster (80-97% similarity). The presence of a class 1 integron and bla(TEM-1) genes is described for the first time among STEC isolates in Brazil and clearly represents a public health concern.

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.

Set of virulence genes and genetic relatedness of O113 : H21 Escherichia coli strains isolated from the animal reservoir and human infections in Brazil

Escherichia coli strains of serotype O113 : H21 are commonly described as belonging to a Shiga toxin (Stx)-producing E. coli (STEC) pathotype worldwide. Albeit this STEC serotype is frequently identified among cattle and other domestic animals, to the best of our knowledge no human infections associated with STEC O113 : H21 have been registered in Brazil to date. Here, we report the virulence profile and genetic relatedness of a collection of O113 : H21 E. coli strains mainly isolated from the animal reservoir aimed at determining their potential as human pathogens. The strains from the animal reservoir (n=34) were all classified as STEC, whereas the few isolates recovered so far from human diarrhoea (n=3) lacked stx genes. Among the STEC, the stx 2d-activatable gene was identified in 85 % of the strains that also carried lpfA O113, iha, saa, ehxA, subAB, astA, cdt-V, espP, espI and epeA; the human strains harboured only lpfA O113, iha and astA. All the strains except one, isolated from cattle, were genetically classified as phylogenetic group B1. High mass plasmids were observed in 25 isolates, but only in the STEC group were these plasmids confirmed as the STEC O113 megaplasmid (pO113). Many closely related subgroups (more than 80 % similarity) were identified by PFGE, with human isolates clustering in a subgroup separate from most of the animal isolates. In conclusion, potentially pathogenic O113 : H21 STEC isolates carrying virulence markers in common with O113 : H21 clones associated with haemolytic uraemic syndrome cases in other regions were demonstrated to occur in the natural reservoir in our settings, and therefore the risk represented by them to public health should be carefully monitored.

Subtilase cytotoxin-encoding subAB operon found exclusively among Shiga toxin-producing Escherichia coli strains

The presence of subAB was investigated for 3,453 Escherichia coli strains of various pathogenic categories. The occurrence of other virulence genes in subAB-positive strains was investigated. The subAB operon was detected among some Shiga toxin-producing E. coli (STEC) serotypes devoid of eae and carrying ehxA. Most subAB-positive strains also harbored stx2, iha, saa, and lpfA(O113).