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1.
A total of 42 Shiga toxin-producing (STEC) strains from slaughtered healthy cattle in Switzerland were characterized by phenotypic and genotypic traits. The 42 sorbitol-positive, non-O157 STEC strains belonged to 26 O:H serotypes (including eight new serotypes) with four serotypes (O103:H2, O113:H4, O116:H-, ONT:H-) accounting for 38.1% of strains. Out of 16 serotypes previously found in human STEC (71% of strains), nine serotypes (38% of strains) were serotypes that have been associated with hemolytic-uremic syndrome (HUS). Polymerase chain reaction (PCR) analysis showed that 18 (43%) strains carried the stx1 gene, 20 strains (48%) had the stx2 gene, and four (9%) strains had both stx1 and stx2 genes. Of strains encoding for stx2 variants, 63% were positive for stx2 subtype. Enterohemolysin (ehxA), intimin (eae), STEC autoagglutinating adhesin (saa) were detected in 17%, 21%, and 19% of the strains, respectively. Amongst the seven intimin-positive strains, one possessed intimin type beta1 (O5:H-), one intimin gamma1 (O145:H), one intimin gamma2/theta, (O111:H21), and four intimin epsilon (O103:H2). The strains belonged to 29 serovirotypes (association between serotypes and virulence factors). O103:H2 stx1eae-epsilon ehxA, O116:H- stx2, and ONT:H- stx2c were the most common accounting for 29% of the strains. Only one strain (2.4%) of serovirotype O145:H- stx1stx2eae-gamma1ehxA showed a pattern of highly virulent human strains. This is the first study providing characterization data of bovine non-O157 STEC in Switzerland, and underlining the importance of the determination of virulence factors (including intimin types) in addition to serotypes to assess the potential pathogenicity of these strains for humans.  相似文献   

2.
Shiga toxin-producing Escherichia coli (STEC) O128:H2 is recognised worldwide to be an important non-O157 STEC associated with human illness and in particular with causing haemolytic uraemic syndrome. This serotype is commonly isolated from sheep and is being increasingly isolated from deer. We determined the virulence profile and genetic relationships of one human, six sheep and five deer intimin-negative STEC O128:H2 strains isolated in Spain over a 7-year period. Our goals were to establish the presence of other virulence-associated factors, such as SubAB, in intimin-negative STEC O128:H2 strains involved in human disease and in that case, to determine if sheep and/or deer represent a reservoir of SubAB-positive STEC O128:H2. All the strains lacked the eae gene and carried subtilase cytotoxin (SubAB) encoding genes (subAB) and tia genes, but not saa gene, suggesting the presence of the recently identified new variant of SubAB, encoded on a putative pathogenicity island together with tia. We report for the first time the presence of subtilase cytotoxin encoding genes in intimin-negative STEC O128:H2 strains pathogenic for humans and how this finding might explain their clinical relevance despite neither carrying eae nor stx subtypes associated with severe clinical outcomes, but only stx1c and stx2b. Multilocus sequence typing analysis revealed that STEC O128:H2 strains from sheep and deer belong to the clonal lineage of STEC O128:H2 strains involved in diarrhoeal and haemorrhagic diseases in humans. Our results indicate that sheep and deer represent a reservoir of SubAB-positive STEC O128:H2 strains and thus a potential source of human infection.  相似文献   

3.
Shiga toxin (Stx)-producing Escherichia coli (STEC) strains isolated from animals and food in Argentina (n=44) and Brazil (n=20) were examined and compared in regard to their phenotypic and genotypic characteristics to evaluate their pathogenic potential. The clonal relatedness of STEC O157 isolates (n=22) was established by phage typing (PT) and pulsed-field gel electrophoresis (PFGE). All O157 strains studied carried eae and enterohemorrhagic E. coli (EHEC)-hly sequences. In Argentina, these strains occurred both in cattle and meat, and 50% of them carried stx2/stx2vh-a genes, whereas in Brazil the O157 strains were isolated from animals, and most harbored the stx2vh-a sequence. At least 13 different O:H serotypes were identified among the non-O157 strains studied, with serotype O113:H21 being found in both countries. All but one non-O157 strains did not carry eae gene, but EHEC-hlyA gene was found in 85.7% of them, and the stx2 genotype was also more prevalent in Argentina than in Brazil (P<0.01), where stx1 alone or in association was most common (68.8%). One STEC strain isolated from a calf in Brazil harbored the new variant referred to as stx2-NV206. PFGE analysis showed that STEC O157 strains were grouped in four clusters. One Brazilian strain was considered possibly related (> or =80%) to Argentinean strains of cluster I. Differences in the pathogenic potential, especially in regard to serotypes and stx genotypes, were observed among the STEC strains recovered from animals and food in both countries.  相似文献   

4.
AIMS: To serotype a subset of Shiga toxin-producing Escherichia coli (STEC) isolates from cattle and sheep to determine whether any corresponding serotypes have been implicated in human diarrhoeal disease, both in New Zealand and worldwide, and to examine the distribution of STEC and enteropathogenic Escherichia coli (EPEC) amongst cattle (calves, heifers and dairy) and sheep (lambs, rams and ewes), to assess whether carriage of identified bacterial genotypes may be associated with a particular age of animal. METHODS: Recto-anal mucosal swabs (RAMS) were taken from 91 calves, 24 heifers and 72 dairy cattle, and 46 lambs, 50 ewes and 36 rams, from four sites in the Manawatu and Rangitikei regions of New Zealand. Strains of E. coli selected from primary isolation plates were subjected to a multiplex polymerase chain reaction (PCR), to determine the presence of Shiga toxin genes (stx1 and stx2) and the E. coli attaching and effacing gene (eae). RESULTS: Overall, 186/319 (58.3%) animals sampled were positive for stx1, stx2, or eae isolates. More sheep (43.9%) were stx1-positive than cattle (2.7%; p = 0.036), and amongst sheep more lambs and ewes were stx1-positive than rams (p = 0.036). Amongst cattle, more calves and heifers were eae-positive than dairy cows (p = 0.030). Two or more different STEC were isolated from at least 28 (9%) animals (three cattle and 25 sheep), based on their stx/eae genotype. Enterohaemolysin genes were found in 39/51 (76%) isolates serotyped. Twenty-one different serotypes were detected, including O5:H-, O9:H51, O26:H11, O84:H-/H2 and O149:H8 from cattle, and O26:H11, O65:H-, O75:H8, O84:H-, O91:H-, O128:H2 and O174:H8 from sheep; O84:H-, O26:H11, O5:H-, O91:H- and O128:H2 serotypes have been associated with human disease. CONCLUSIONS: If nationally representative, this study confirms that cattle and sheep in New Zealand may be a major reservoir of STEC serotypes that have been recognised as causative agents of diarrhoeal disease in humans. Distribution of STEC and EPEC in cattle and sheep indicates that direct contact with, in particular, calves or their faeces, or exposure to environments cross contaminated with ruminant faeces, may represent an increased risk factor for human disease in New Zealand.  相似文献   

5.
Faecal samples from 76 diarrhoeic calves belonging to 36 farms located in the Pampas plain, Argentina, were examined for Shiga toxin-producing Escherichia coli (STEC). A total of 15 STEC strains were isolated from 12 (15.8%) calves which came from six different farms. All stx positive strains assayed by PCR were also positives in the Vero cell cytotoxicity test. The majority (60.0%) of the STEC strains carried the stx(1) gene. Twelve (80.0%) of the STEC isolates which belonged to serotypes O5:H- (n = 4), O26:H11 (n = 4), O26:H- (n = 1), O111:H- (n = 2), and O123:H38 (n = 1) were also enterohaemolysin (EHly) positive and carried the gene encoding for intimin (eae). All the stx positive strains were negative for the bfpA gene. Localized adherence to HEp-2 cells were observed in 83.3% of the eae+ STEC strains. STEC belonging to serotype O5:H- showed atypical biochemical properties, including urease production. Urease was also produced by two strains belonging to serotypes O153:H? and non-typeable, respectively. Resistance to three or more antibiotics was observed in 12 (80.0%) of the STEC isolates. Most of the serotypes of STEC recovered in this survey carried virulence traits that are associated with increased human and bovine pathogenicity. The present study shows that highly virulent STEC strains are being shed by diarrhoeic calves from farms located in a high incidence area of human STEC infections.  相似文献   

6.
Three-hundred and forty-five herds (17 swine, 122 dairy sheep, 124 beef and 82 dairy cattle) were investigated for prevalence of Shiga toxin-producing Escherichia coli (STEC). Rectal faecal samples were selectively enriched and then examined by immunodetection techniques (Immunomagnetic Separation with anti-E. coli O157 Dynabeads, ImmunoMagnetic cell Separation (IMS) and automated enzyme-linked fluorescent immunoassay using VIDAS) and polymerase chain reaction (PCR) (rfbE and fliC genes) to assess the prevalence of E. coli O157:H7. Prevalence of non-O157 STEC was estimated by PCR screening for stx genes of 10 lactose-positive colonies grown on MacConkey agar after enrichment. PCR was used on all STEC isolates to detect stx(1), stx(2), eaeA and E-hlyA genes. Both immunodetection methods showed a moderate-good level of agreement (kappa = 0.649) but IMS showed 87.5% complementary sensitivity. Prevalence of positive herds for E. coli O157:H7 was estimated at 8.7% for sheep and 3.8% for cattle, whereas all the porcine herds tested negative. Non-O157 STEC were also absent from swine, but were isolated more frequently from ovine (50.8%) than bovine herds (35.9%). Within-herd prevalences of excretion of E. coli O157:H7 established by individual testing of 279 sheep (six herds) and 30 beef cattle (one herd) were 7.3% and 6.7% respectively. PCR analysis of 49 E. coli O157:H7 and 209 non-O157 isolates showed a different distribution of virulence genes. All E. coli O157:H7 were stx(2) gene-positive, eaeA was detected in 95.9%, and the toxigenic profile stx(2)/eaeA/E-hlyA was present in 75.5% of the isolates. Among the non-O157 STEC, prevalence of eaeA was significantly lower (5.3%) and E-hlyA was present in 50.2% of the isolates but only sporadically associated with eaeA. stx(2) was predominant in non-O157 isolates from cattle, whereas in sheep the combination stx(1)/stx(2) was more prevalent. This study demonstrated the wide distribution of STEC in ruminant herds, which represent an important reservoir for strains that pose a potential risk for human infections.  相似文献   

7.
Recently, virulence patterns of Stx2e-producing Escherichia coli from pigs with edema disease and from humans were compared and strains from diseased pigs were reported to be unlikely human pathogens [Sonntag, A.K., Bielaszewska, M., Mellmann, A., Dierksen, N., Schierack, P., Wieler, L.H., Schmidt, M.A., Karch, H., 2005. Shiga toxin 2e-producing Escherichia coli isolates from humans and pigs differ in their virulence profiles and interactions with intestinal epithelial cells. Appl. Environ. Microbiol. 71, 8855-8863]. In the present study, 31 Shiga toxin-producing E. coli (STEC) strains harboring stx2e, which were previously isolated out of fecal samples from healthy pigs at slaughter [Kaufmann, M., Zweifel, C., Blanco, M., Blanco, J.E., Blanco, J., Beutin, L., Stephan, R., 2006. Escherichia coli O157 and non-O157 Shiga toxin-producing Escherichia coli in fecal samples of finished pigs at slaughter in Switzerland. J. Food Prot. 69, 260-266], were characterized by phenotypic and genotypic traits. Nine of the thirty-one sorbitol-positive non-O157 STEC (stx2e) isolated from healthy pigs belonged to serotypes found in STEC isolated from humans, including two serotypes (O9:H-, O26:H-) reported in association with hemolytic-uremic syndrome. Otherwise, the serotypes were different from those isolated from cases of edema disease in pigs. The eae (intimin) gene, which is strongly correlated with severe human disease, was not detected. Moreover, all strains were lacking the genes for enterohemolysin (ehxA), porcine A/E associated protein (paa), STEC autoagglutinating adhesin (saa) and the serin protease EspI (espI). Nine strains tested positive for astA (EAST1), one O141:H17 strain for fedA (F18 fimbrial adhesin) and one O159:H- strain for terF (tellurite resistance). Similar to the Stx2e-producing E. coli isolated from humans, which are mainly lacking further virulence factors, genes of an iron uptake system on the high-pathogenicity island (irp2, fyuA) were detected in three ONT:H10 and ONT:H19 strains from healthy pigs. Consequently, although the isolated strains are unlikely to be associated with severe human diseases, healthy pigs cannot be excluded as a potential source of human infection with Stx2e-producing STEC.  相似文献   

8.
Shiga toxin-producing Escherichia coli (STEC) are a public health concern. Bacterial culture techniques commonly used to detect E. coli O157:H7 will not detect other STEC serotypes. Feces from cattle and other animals are a source of O157:H7 and other pathogenic serotypes of STEC. The objective of this study was to estimate the pen-level prevalence of Shiga toxins and selected STEC serotypes in pre-slaughter feedlot cattle. Composite fecal samples were cultured and a polymerase chain reaction (PCR) was used to detect genes for Shiga toxins (stx1 and stx2) and genes for O157:H7, O111:H8, and O26:H11 serotypes. Evidence of Shiga toxins was found in 23 pens (92%), O157:H7 in 2 (8%), O111:H8 in 5 (20%), and O26:H11 in 20 (80%) of the 25 pens investigated. Although pen-level prevalence estimates for Shiga toxins and non-O157 serotypes seem high relative to O157:H7, further effort is required to determine the human health significance of non-O157 serotypes of STEC in feedlot cattle.  相似文献   

9.
A multiplex real-time PCR (R-PCR) assay was designed and evaluated on the ABI 7700 sequence detection system (TaqMan) to detect enterohemorrhagic Escherichia coli (EHEC) O157:H7 in pure cultures, feces, and tissues. Three sets of primers and fluorogenic probes were used for amplification and real-time detection of a 106-bp region of the eae gene encoding EHEC O157:H7-specific intimin, and 150-bp and 200-bp segments of genes stx1 and stx2 encoding Shiga toxins 1 and 2, respectively. Analysis of 67 bacterial strains demonstrated that the R-PCR assay successfully distinguished EHEC O157:H7 serotype from non-O157 serotypes and provided accurate profiling of genes encoding intimin and Shiga toxins. Bacterial strains lacking these genes were not detected with this assay. The detection range of the R-PCR assay for the three genes was linear over DNA concentrations corresponding from 10(3) to 10(8)CFU/ml of EHEC O157:H7. The R-PCR allowed construction of standard curves that facilitated quantification of EHEC O157:H7 in feces and intestinal tissues. Detection sensitivity of the R-PCR assay ranged from 10(4) to 10(8)CFU/g of feces or tissues without enrichment. Enrichment of feces in a non-selective broth for 4 and 16h resulted in the detection of levels (from 10(0) to 10(3)CFU/g of feces) considered sufficient for infection in humans. The R-PCR assay for eae(O157:H7), stx1, and stx2 proved to be a rapid test for detection of EHEC O157:H7 in complex biological matrices and could also potentially be used for quantification of EHEC O157:H7 in foods or fecal samples.  相似文献   

10.
In order to determine the occurrence, serotypes and virulence markers of Shiga toxin-producing Escherichia coli (STEC) strains, 153 fecal samples of cattle randomly selected from six dairy farms in Sao Paulo State, Brazil, were examined for Shiga toxin (Stx) production by the Vero cell assay. Feces were directly streaked onto MacConkey Sorbitol Agar and incubated at 37 degrees C overnight. Sorbitol-negative colonies (maximum 20) and up to 10 sorbitol-positive colonies from each plate were subcultured onto presumptive diagnostic medium IAL. Sorbitol-negative isolates were screened with O157 antiserum for identification of O157:H7 E. coli. Isolates presenting cytotoxic activity were submitted to colony hybridization assays with specific DNA probes for stx1, stx2, eae, Ehly and astA genes. The isolation rate of STEC ranged from 3.8 to 84.6% depending on the farm analysed. STEC was identified in 25.5% of the animals, and most of them (64.1%) carried a single STEC serotype. A total of 202 STEC isolates were recovered from the animals, and except for the 2 O157:H7 isolates all the others expressed cytotoxic activity. The great majority of the STEC isolates carried both stx1 and stx2 genes (114/202, 56.4%) or stx2 (82/202, 40.6%); and whereas the Ehly sequence occurred in most of them (88%) eae was only observed in O157:H7 and O111:HNM isolates. Serotypes O113:H21, O178:H19 and O79:H14 were the most frequent STEC serotypes identified and widely distributed among animals from different farms, while others such as O77:H18, O88:H25 and O98:H17 occurred only in particular farms. This is the first report on the occurrence of STEC in dairy cattle in Sao Paulo State, and the results point to substantial differences in rate of isolation, serotypes and genetic profile of STEC that has been previously described among beef cattle in our community. Moreover, to our knowledge O79:H14 and O98:H17 represent new STEC serotypes, while O178:H19 has only been recently reported in Spain.  相似文献   

11.
The virulence properties of Shiga toxin-producing Escherichia coli (STEC) strains isolated from diarrhoeic and non-diarrhoeic calves were compared. The strains were also tested for O157:H7, O111 and O26 serotypes, using PCR and conventional serotyping methods. E coli strains isolated from 297 faecal samples, from 200 diarrhoeic and 97 non-diarrhoeic calves, were screened by multiplex PCR assay for the stx1, stx2, eae and Ehly virulence genes. STECs were recovered from 8 per cent of diarrhoeic calves and 10.3 per cent of non-diarrhoeic calves. The predominant virulence gene profile was stx1/eae/Ehly (47.3 per cent) among isolates from diarrhoeic calves and eae/Ehly (36.8 per cent) among isolates from non-diarrhoeic calves. Among three tested serogroups, the predominant serogroup was O26 (18.4 per cent), and O157:H7 was not detected. Intimin subtyping by restriction fragment length polymorphism analysis revealed only three intimin subtypes (β, γ and ). A significant difference was observed in the distribution of Int- between two groups. Int- was present in 50 per cent of the isolates from diarrhoeic calves and in 11.1 per cent of the isolates from non-diarrhoeic calves; this difference was statistically significant (P=0.01).  相似文献   

12.
Some Shiga toxin-producing Escherichia coli strains (STEC), and in particular E. coli O157:H7, are known to cause severe illness in humans. STEC have been responsible for large foodborne outbreaks and some of these have been linked to dairy products. The aim of the present study was to determine the dissemination and persistence of STEC on 13 dairy farms in France, which were selected out of 151 randomized dairy farms. A total of 1309 samples were collected, including 415 faecal samples from cattle and 894 samples from the farm environment. Bacteria from samples were cultured and screened for Shiga toxin (stx) genes by polymerase chain reaction (PCR). STEC isolates were recovered from stx-positive samples after colony blotting, and characterized for their virulence genes, serotypes and XbaI digestion patterns of total DNA separated by pulsed-field gel electrophoresis (PFGE). Stx genes were detected in 145 faecal samples (35%) and 179 (20%) environmental samples, and a total of 118 STEC isolates were recovered. Forty-six percent of the STEC isolates were positive for stx1, 86% for stx2, 29% for intimin (eae-gene) and 92% for enterohemolysin (ehx), of which 16% of the STEC strains carried these four virulence factors in combination. Furthermore, we found that some faecal STEC strains belonged to serotypes involved in human disease (O26:H11 and O157:H7). PFGE profiles indicated genetic diversity of the STEC strains and some of these persisted in the farm environment for up to 12 months. A large range of contaminated samples were collected, in particular from udders and teats. These organs are potential sources for contamination and re-contamination of dairy cattle and constitute an important risk for milk contamination.  相似文献   

13.
《Veterinary microbiology》2015,175(1):150-156
Sheep constitute an important source of zoonotic pathogens as Shiga toxin-producing Escherichia coli (STEC). In this study, the prevalence, serotypes and virulence profiles of STEC were investigated among 130 healthy sheep from small and medium farms in southern Brazil. STEC was isolated from 65 (50%) of the tested animals and detected in all flocks. A total of 70 STEC isolates were characterized, and belonged to 23 different O:H serotypes, many of which associated with human disease, including hemolytic-uremic syndrome (HUS). Among the serotypes identified, O76:H19 and O65:H– were the most common, and O75:H14 and O169:H7 have not been previously reported in STEC strains. Most of the STEC isolates harbored only stx1, whereas the Stx2b subtype was the most common among those carrying stx2. Enterohemolysin (ehxA) and intimin (eae) genes were detected in 61 (87.1%) and four (5.7%) isolates, respectively. Genes encoding putative adhesins (saa, iha, lpfO113) and toxins (subAB and cdtV) were also observed. The majority of the isolates displayed virulence features related to pathogenesis of STEC, such as adherence to epithelial cells, high cytotoxicity and enterohemolytic activity. Ovine STEC isolates belonged mostly to phylogenetic group B1. PFGE revealed particular clones distributed in some farms, as well as variations in the degree of genetic similarity within serotypes examined. In conclusion, STEC are widely distributed in southern Brazilian sheep, and belonged mainly to serotypes that are not commonly reported in other regions, such as O76:H19 and O65:H–. A geographical variation in the distribution of STEC serotypes seems to occur in sheep.  相似文献   

14.
为了了解新疆伊犁地区肉牛屠宰过程中大肠杆菌的污染情况,检测非O157致病性产志贺毒素大肠杆菌(Shiga toxin-producing Escherichia coli,STEC)的感染情况,本试验采集新疆伊犁地区某定点肉牛屠宰场中屠宰肉牛的粪样和屠宰后的胴体表面拭子,并对样品进行了大肠杆菌的分离鉴定、毒力基因(eae、stx1、stx2)的PCR检测、O157鉴定(rfbE)、ERIC-PCR基因分型和小鼠致病性试验。结果显示,在采集的45份样品中分离鉴定出42株大肠杆菌,分离率为93.3%。其中2株菌株同时编码了毒力基因stx1和stx2,检出率为4.8%,毒力基因eae未被检出。PCR鉴定均为非O157 STEC。ERIC-PCR基因分型检测发现,2株菌的基因型非常相似,同源关系密切。对小鼠进行腹腔注射攻毒,攻菌6 h后,小鼠开始出现死亡,立即解剖死亡小鼠发现,其肠道出血,肝脏、脾脏、肾脏明显出血肿大,解剖对照小鼠表现正常,表明菌株具有一定的致病性。综上所述,在肉牛屠宰过程中存在大肠杆菌污染,其中粪便中非O157 STEC菌株对胴体造成了污染,需要加强控制肉牛的屠宰加工关键环节的环境卫生。  相似文献   

15.
Grazing-fed cattle were previously demonstrated to be reservoir of non-O157 Shigatoxigenic Escherichia coli (STEC) serotypes in Argentina. The acid-resistance of some STEC strains makes it reasonable to assume the presence in feedlot of particular STEC serotypes. Fifty-nine animals were sampled every 2 weeks during 6 months by rectal swabs. Twenty-seven of 59 animals (45.8%) were shown to be Stx2(+); 3/59 (5.1%) carried Stx1(+) and 7/59 (11.9%) were Stx1(+) Stx2(+). Among 44 STEC isolates, 31 isolates were associated to 10 O serogroups (O2, O15, O25, O103, O145, O146, O157, O171, O174, O175) and 13 were considered non-typable (NT). Six H antigens (H2, H7, H8, H19, H21, H25) were distributed in 21 isolates whereas 23 were non-mobile (H-). Seventeen of 44 strains (38.6%) were eaeA(+) and 14 (31.8%) harbored the 60MDa plasmid. The megaplasmid (Mp) and eaeA gene were simultaneously found in a limited number of serotypes belonging to the enterohaemorrhagic E. coli (EHEC). E. coli O157:H7 strains, isolated from four (6.8%) animals, corresponded to the Stx2(+), eaeA(+), Mp(+) pattern. Three O157:H7 strains belonged to phage type 4 and the other strain was atypical. Many serotypes isolated from grain-fed cattle (O2:H25, O15:H21, O25:H19, O145:H-, O146:H-, O146:H21, O157:H7, O175:H8) also differed from those isolated by us previously from grazing animals. The serotypes O15:H21, O25:H19 and O175:H8 had not been identified at present as belonging to STEC. This work provides new data for the understanding of the ecology of STEC in grain-fed cattle and confirms that cattle are an important reservoir of STEC.  相似文献   

16.
Shiga toxin producing-Escherichia coli (STEC) is an important emerging pathogen, and ruminants are recognized as their main natural reservoir. The aim of this work was to establish the frequency of STEC in non-domestic mammals of the Zoo and Botanical Garden of La Plata City, Argentina, and to pheno-genotypically characterize STEC isolates. By polymerase chain reaction (PCR), Shiga toxin (stx) gene sequences were detected in 50.8% of 65 fecal samples. Twenty-five STEC strains were isolated from 38.5% of the Zoo's animals. Ten species of order Cetartiodactyla and one species of order Rodentia were recognized as new STEC carriers. STEC strains belonged to 7 different serotypes including new serotypes O12:H25 and O13:H6. Serotype O146:H28, previously associated with human infections, represented 24% of STEC isolates. The most frequent Shiga toxin identified were type 1c and type 2c. Nineteen strains were positive for iha gene, 8 strains were positive for ehxA gene. Moreover, all strains were positive for lpfAO113 and negative for rfbO157, eae, saa, lpfAO157/OI-141, lpfAO157/OI-154, efa1, and toxB genes. Results obtained by XbaI-pulsed-field gel electrophoresis (XbaI-PFGE) confirmed the transmission of STEC strains among different animal species and suborders. In addition, we observed a potential association between STEC-harboring animal and factors such as belonging to order Cetartiodactyla, living in a pit, and belonging to a non-autochthonous species. This is the first work developed with zoological mammals and STEC in Argentina.  相似文献   

17.
The aims of this study were to determine the prevalence of Shiga toxin-producing Escherichia coli (STEC) strains in pigs as a possible STEC reservoir in India as well as to characterize the STEC strains and to determine the antimicrobial resistance pattern of the strains. A total of 782 E. coli isolates from clinically healthy (n?=?473) and diarrhoeic piglets (309) belonging to major pig-producing states of India were screened by the polymerase chain reaction (PCR) assay for the presence of virulence genes characteristic for STEC, that is, Shiga toxin-producing gene(s) (stx1, stx2), intimin (eae), enterohemolysin (hlyA) and STEC autoagglutinating adhesin (Saa). Overall STEC were detected in 113 (14.4 %) piglets, and the prevalence of E. coli O157 and non-O157 STEC were 4 (0.5 %) and 109 (13.9 %), respectively. None of the O157 STEC isolates carried gene encoding for H7 antigen (fliCh7). The various combinations of virulence genes present in the strains studied were stx1 in 4.6 %, stx1 in combination with stx2 gene in 5.1 %, stx1 in combination with stx2 and ehxA in 0.6 %, stx1 in combination with stx2 and eae in 0.2 % and stx2 alone in 3.7 %. All STEC isolates were found negative for STEC autoagglutinating adhesin (Saa). The number of STEC isolates which showed resistance to antimicrobials such as ampicillin, tetracycline, streptomycin, lincomycin, nalidixic acid, sulfadiazine, penicillin, gentamicin, kanamycin and ceftriaxone were 100, 99, 98, 97, 95, 94, 92, 88, 85 and 85, respectively. Ninety-seven isolates showed resistance to more than 2 antimicrobials, and 8 resistance groups (R1 to R8) were observed. This study demonstrates that pigs in India harbour both O157 and non-O157 STEC, and this may pose serious public health problems in future.  相似文献   

18.
The importance of latent zoonoses has increased in recent years in view of foodborne diseases: (i) the "healthy" animal repesents a reservoir for specific pathogens; () no pathological-anatomical changes in the carcass and its organs show the presence of these pathogens; and (iii) these pathogens may enter the food chain via hygienic weak points in the slaughtering process. To estimate the risks involved and to take appropriate measures, analysis of the slaughtering process should be complemented by collecting data relating to the carriage of the animals of latent zoonotic pathogens. From October 2004 to June 2005, fecal samples from 630 slaughtered sheep were enriched and then examied by IMS technique and by PCR to assess the prevalence of E. coli O157 (OE). Seven samples (1.1%), distributed throughout the whole examination period, were found to be positive. To assess the potential pathogenicity for humans, E. coli O157 strains were isolated by colony hybridization and further characterized. The isolated strains fermented Sorbitol, showed four different H tys (H7, H12, H38, H48), and were all negative for stx. One O157:H7 strain harbored the gene for intimin (eae) in combination with ehxA, and paa. In consequence, the potential health hazard from sheep meat related to O157 STEC seems current not to be of particular importance in Switzerland. Results emphasize the fact that E. coli O157 are not always STEC but may belong to other pathotypes as nontraditional EPEC.  相似文献   

19.
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.  相似文献   

20.
Pets can be reservoirs of Shiga toxin-producing Escherichia coli (STEC) strains. The aim of this study was to examine nine strains belonging to several serotypes (O91:H21, O91:H16, O178:H19, O8:H19, O22:H8, O22:HNT, ONT:H8), previously recovered from cats or dogs. To this end, we assessed a set of additional virulence genes (stx(2) subtype, subAB, ehxA, eae and saa), cytotoxic activity, and genetic relationships with strains isolated from cattle, meat and humans using pulsed-field gel electrophoresis (PFGE). Most of the isolates carried the stx(2) and/or stx(2vh-b) sequences, while only the O91:H21 isolate presented the mucus-activatable stx(2d) variant, as confirmed by sequencing the genes of subunits A and B. All the strains showed cytotoxic activity in cultured cells. One of the two O178:H19, selected for its high level of cytotoxicity in Vero cells, showed the ability to cause functional alterations in the human colon mucosa in vitro. None of the strains possessed the subAB, eae or saa genes and only the strains belonging to serotype O8:H19 carried the ehxA gene. The isolates shared 90-100% similarity by PFGE to epidemiologically unrelated strains of the corresponding serotypes recovered from cattle, meat or humans. Our results demonstrate that dogs and cats may have a role in the infection of humans by STEC, probably serving as a vehicle for bovine strains in the cycle of human infection, and thus emphasize the health risks for owners and their families.  相似文献   

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