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1.
Escherichia coli strains producing a variant of Shiga toxin 2 (Stx2), designated Stx2f, have been recently described in the stools of feral pigeons. During 1997-1998, 649 pigeons were trapped and examined in three different squares of Rome. Stool samples were collected from each bird and enrichment cultures were examined for the presence of Stx by the vero cell assay. Stx-producing E. coli (STEC) were isolated from the positive cultures and characterized by serotyping and PCR analysis of stx and other virulence-related genes. Stx was detected in 10.8% of the stool enrichment cultures. The percentage of positive birds did not differ significantly for the three flocks considered and the season of sample collection. Conversely, STEC carriage was significantly more frequent in young than in adult birds (17.9 versus 8.2%). None of the birds examined showed signs of disease. STEC strains were isolated from 30 of 42 Stx-positive cultures examined. All the strains produced Stx2f, and most of them possessed genes encoding for intimin and the cytolethal distending toxin (CLDT). Six serogroups were identified, but most of the isolates belonged to O45, O18ab, and O75. Molecular typing indicated that most of the isolates within a flock were clonally-related. This work confirms that pigeons represent a natural reservoir of STEC strains characterized by the production of the toxin variant Stx2f, and by the frequent presence of eae and cldt genes. Further work is needed to clarify whether these STEC may represent a cause of avian disease or even a potential health hazard for humans.  相似文献   

2.
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   

3.
The role of birds as sources of Shiga toxin-and intimin-producing Escherichia coli was studied. Fecal samples from live gulls (n=86), pigeons (n=33) and broiler chickens (n=199) from 23 flocks were analyzed for stx and eae by PCR. No stx positive samples were detected. In contrast, eae E. coli were highly prevalent among gulls (40%), and was also found in pigeons (7%) and chickens (57% of the flocks contaminated). The eae positive isolates were analyzed genetically and O-serogrouped. One isolate from a pigeon was found to have stx (2f). The isolates of gulls differed from those of pigeons and chickens, and all eae E. coli isolates from birds differed from human pathogenic strains by the lack of EHEC-hlyA and bfp/EAF as well as distribution of O-serogroups. Thus, birds cannot be regarded as important carriers of zoonotic stx or eae E. coli in Finland.  相似文献   

4.
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   

5.
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6.
One hundred and ten clinical Escherichia coli isolates of serovar O157 (n = 102) and O26 (n = 8) were characterized for the presence of putative virulence genes by PCR. All but one of these isolates contained the eae gene. The EHEC-hly gene could be detected in all E. coli O157 and in 50% of E. coli O26 isolates. Forty-five (40.9%) of the 110 E. coli were positive for both stx(1) and stx(2) genes, 2 (1.8%) isolates were positive for stx(1) and 57 isolates (51.8%) were positive for stx(2) only. Among the 102 stx(2) positive isolates, 14 (13.7%) E. coli O157 contained also the stx(2c) variant gene. No other stx(2) variant was identified. Six clinical isolates (five E. coli O157:H7 and one E. coli O26) did not contain stx genes. Ten non-pathogenic E. coli isolates which were amplified as controls didn't contain any stx and eae gene but two of the ten strains contained the EHEC-hly gene. By their growth on chromogenic media, all but two of 50 E. coli O157 could be differentiated from eight E. coli O26 and 10 non-pathogenic E. coli. Sixty-one of the O157:H7 isolates were further subjected to pulsed-field gel electrophoresis (PFGE) which identified 49 distinguishable patterns. In five cases where contact infection among family members was suspected, indistinguishable PFGE patterns confirmed the epidemiological relatedness of the isolates. Moreover, two PFGE clusters were identified which comprised five and three strains, respectively. These findings indicate the occurrence of both family and diffuse outbreaks of E. coli O157 infections in Austria during recent years and demonstrate the need for molecular subtyping of these pathogens.  相似文献   

7.
In order to evaluate the prevalence of Shiga toxin-producing Escherichia coli (STEC) strains, 197 fecal samples of healthy cattle from 10 dairy farms, four beef farms and one slaughterhouse at Rio de Janeiro State, Brazil, were examined for Shiga toxin (Stx) gene sequences by polymerase chain reaction (PCR). For presumptive isolation of O157:H7 E. coli, the Cefixime-potassium tellurite-sorbitol MacConkey Agar (CT-SMAC) was used. A high occurrence (71%) of Stx was detected, and was more frequently found among dairy cattle (82% vs. 53% in beef cattle), in which no differences were observed regarding the age of the animals. Dot blot hybridization with stx1 and stx2 probes revealed that the predominant STEC type was one that had the genes for both stx1 and stx2 in dairy cattle and one that had only the stx1 gene for beef cattle. Three (1.5%) O157:H7 E. coli strains were isolated from one beef and two dairy animals by the use of CT-SMAC. To our knowledge, this is the first report of O157:H7 isolation in Brazil. A PCR-based STEC detection protocol led to the isolation of STEC in 12 of 16 randomly selected PCR-positive stool samples. A total of 15 STEC strains belonging to 11 serotypes were isolated, and most of them (60%) had both stx1 and stx2 gene sequences. Cytotoxicity assays with HeLa and Vero cells revealed that all strains except two of serotype O157:H7 expressed Stx. The data point to the high prevalence of STEC in our environment and suggest the need for good control strategies for the prevention of contamination of animal products.  相似文献   

8.
The objectives of the research were to determine the presence of the gene sequences for Shiga Toxin 2e (Stx2e), enterotoxins (ST-I, ST-II and LT-I), and F18 fimbriae in 144 Escherichia coli strains isolated from pigs with edema disease; to assess the ability of stx2e(+) strains to produce Stx2e; and to determine the O serogroups of the E. coli strains. Presence of the genes was determined by polymerase chain reaction (PCR), production of Stx2e was assessed by cytotoxicity for Vero and Hela cells, O serogroups were identified by agglutination with specific antisera. Of the 144 strains tested, 99 were stx2e(+) by PCR, but only 45 of these were Stx2e(+) in the cell culture assays. Among the 99 stx2e(+) strains, PCR detected the genes for F18ab, ST-I, ST-II, LT-I in 76, 40, 31 and 16 strains, respectively. Forty-one of the 99 sxt2e(+) strains belonged to O group 139; the rest did not belong to the classical edema disease O serogroups. It is likely that the enterotoxins, whose genes were detected at high frequency, are responsible for diarrhea seem in pigs with edema disease in Brazil.  相似文献   

9.
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   

10.
为了解2009－2010年间在河南、甘肃地区分离鉴定的5株大肠埃希菌O157(E.coli O157)携带stx的情况及不同分离株间stx分子进化与变迁的情况,本研究利用PCR方法对分离株进行了stx基因检测,并完成了序列测定与系统演化分析。结果表明,5株不同动物源的分离株均含有stx1及stx2基因。序列分析结果显示5株分离株间stx1、stx2的核苷酸及氨基酸同源性均较高;stx1基因均与参考株中的山羊源和食品源E.coli O157菌株的同源性较高,进化树中遗传距离最近;分离株的stx2基因与多株牛源及少数人源参考株也具有较高的同源性,进化树中虽然5株分离菌均在一个大主干分支中,但分离株27与其他各分离株及参照株遗传距离最远,独自处于一次级分支中;分离株L37与W、12与50分别分布于牛源、人源E.coli O157小次级分支中;由此可推测,分离株所携带的stx1很有可能是经食品源或羊源E.coli O157传递而来;分离株L37与W、分离株12与50的stx2可能是由牛源、人源E .coli O157菌株传递而来,分离株27的stx2来源不清楚。研究结果表明,5株E.coli O157分离株均含有stx1、stx2基因,但两个基因的起源存在差异。  相似文献   

11.
Cattle are a primary reservoir of Escherichia coli O157:H7, a major foodborne pathogen. The organism causes haemorrhagic colitis which can lead to serious complications, including haemolytic–uraemic syndrome. Although E. coli O157:H7 is widely prevalent in cattle and cattle environments, the number of human cases remain relatively low, suggesting possible strain diversity and differences in virulence between human and bovine strains. Shiga toxins, Stx1 and Stx2, are the major virulence factors. Differences in Stx2 production between human and bovine strains have been demonstrated previously, and isolates possessing the stx2 gene, but not producing Stx2 [toxin non‐producing (TNP) strains] have been identified. In this study, 150 isolates (56 human, 94 bovine) were tested by PCR for stx2 upstream regions associated with TNP and the Q933 gene, which has been previously associated with toxin production. A reverse passive latex agglutination test was used to evaluate 107 isolates (50 human, 57 bovine) for Stx1 and Stx2 production. The percentages of human and bovine isolates positive for presence of the TNP regions were similar (57.1% and 53.1% respectively), while a higher percentage of human isolates was positive for Q933 gene (89.3% versus 54.3%). Stx2 production of ≥1 : 8 was found in 86.0% of human isolates compared with 26.3% of bovine isolates. Bovine isolates with the presence of the TNP regions were associated with significantly lower Stx2 production (P < 0.05), while the Q933 gene was associated with higher Stx2 production (P < 0.05). However, the presence of the TNP region was not associated (P > 0.05) with low Stx2 production in human isolates. Therefore, Q933 was a better indicator of high Stx2 production by human and bovine isolates and may be a useful screening method to assess their potential to cause human disease.  相似文献   

12.
Ten Escherichia coli O157 strains isolated from cattle and children in Poland were investigated by the use of molecular biological methods. All strains possessed the intimin and enterohaemolysin genes and harboured the genetic determinants for Stx2 toxin (five isolates), Stx1 toxin (two strains) or both (three isolates). The genetic relatedness of the strains was examined by restriction fragment length polymorphism (RFLP) of chromosomal DNA digested with Xbal and Notl. Nine closely related RFLP patterns were observed. Comparison of bovine and human E coli O157 isolates based on the analysis of Xbal and Notl digested profiles showed that all strains belonged to one genetic cluster. These results indicate that cattle must be considered as a possible source of human E coli O157 infection in Poland.  相似文献   

13.
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   

14.
This study was undertaken to determine the present distribution of serogroups, hemolytic activity and virulence factors among Escherichia coli strains isolated from pigs with postweaning diarrhoea from eight provinces in eastern China. Two hundred and fifteen E. coli isolates were serogrouped with O-antisera, investigated for hemolytic activity, assessed for F4, F5, F6, F18 and F41 fimbrial antigens by monoclonal antibodies and detected for genes of enterotoxins and shiga-toxin-two-variant (Stx2e) by a multiplex polymerase chain reaction (PCR). Among these E. coli isolates, 140 were determined to be placed in serogroups, 52 were unable to be serogrouped and the rest 23 auto-agglutinated. These isolates distributed in 45 serogroups and 64.3% (90/140) belonged to 12 O serogroups: O8, O9, O11, O20, O32, O91, O93, O101, O107, O115, O116 and O131. Hemolytic activity was detected in 11.6% (25/215) of all isolates. Several uncommon O serogroups were discovered in this study. Agglutination tests showed that 50.2% (108/215) of these isolates were positive for one or more of the five fimbrial antigens. Seventy-two E. coli strains expressed single fimbria and 36 strains expressed two or more fimbriae. Among these 215 E. coli isolates, strains expressing F18, F4, F6, F6 + F18 or F5 + F41 occurred more frequently. PCR analysis showed that 60.5% (130/215) of the isolates only harboured the gene of estI (STI) while 6.0% (13/215) strains possessed the genes of stx2e, estI and estII and 5.6% (12/215) of strains had the genes of estI/estII. Of all these isolates, 107 (49.8%) were negative for the fimbrial antigens examined. The fimbria-negative isolates usually possessed genetic determinant of estI (78, 72.9%).  相似文献   

15.
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   

16.
Shiga toxin producing Escherichia coli (STEC) harbouring the stx(2d-activatable) gene and expressing the mucus- and elastase-activatable phenotype have been associated with severe outcomes of human disease. However, there is limited data available on the occurrence of such strains in livestock reservoirs. In this study, we analyzed 11 STEC strains isolated from healthy cattle and sheep at slaughter that were originally detected to contain the stx(2c) allele, for the presence of the stx(2d-activatable) genotype. Ten of the eleven strains displayed the stx(2d-activatable) genotype as determine by PstI restriction fragment length polymorphism (RFLP) of 890-bp fragments of their stx genes. However, only in 6 of the 10 strains whose stx genes were sequenced, the presence of stx(2d-activatable) could be confirmed based on the predicted amino acid sequence of their StxA subunits; the remaining four strains contained Stx2c A subunit. Five of the six strains which contained stx(2d-activatable) displayed the activatable phenotype on Vero cells. Genes for adhesins such as the outer membrane protein intimin (eae), which is essential for the intimate attachment and the formation of attaching-and-effacing lesions on intestinal epithelial cells, or the STEC autoagglutinating adhesin (saa), potentially important in eae-negative STEC, were not detected. Moreover, all the strains tested negative for EHEC-hlyA encoding enterohaemorrhagic E. coli (EHEC) hemolysin. To our knowledge, this is the first study that reports the presence of STEC harbouring stx(2d-activatable) and producing the activatable Stx2d in fecal samples of sheep. Therefore both cattle and sheep are reservoirs of such strains and potential sources of human infections. This is of particular importance, because in contrast to other eae-negative STEC, strains producing Stx2d(activatable) may cause severe diseases such as bloody diarrhoea and haemolytic uremic syndrome in humans.  相似文献   

17.
E. coli strains isolated from pigs with postweaning diarrhea or edema disease were tested by phenotypic and genotypic methods for the presence of virulence antigens and genes, respectively. The slide agglutination and ELISA analyses were used for determination of F4, F5, F6, F17, and F41 fimbriae whereas the prevalence of fimbrial fedA and toxin eltI, estI, estII, stx1, stx2 and stx2e genes were recorded by the means of PCR. Only F4 antigen (ac variant) was found in strains of the serogroup O149:K91 isolated from pigs with diarrhea. PCR analyses showed that the fedA gene encoding F18 fimbriae was present in 61.9% of strains isolated from pigs with diarrhea and in 84.2% of strains isolated from pigs with edema disease. The eltI genes encoding heat-labile toxin I (LTI) were present only in 9 out of 21 strains recovered from pigs with diarrhea. Shiga toxin 2 variant (stx2e) genes were found in six isolates from edema disease and also in one strain from diarrhea. The PCR test used in the study was a sensitive and valuable method for determination of virulence factors of E. coli strains.  相似文献   

18.
The relationship of the urease operon in the highly virulent O149 porcine enterotoxigenic Escherichia coli (ETEC) strain Ro8 to a genomic island (GI) homologous to O island (OI) 48 of O157 enterohemorrhagic E. coli (EHEC) strain EDL933 was investigated. Eighty-four of 84 O149:H10 strains were urease positive whereas 44 of 44 O149:H43 porcine ETEC strains were urease-negative. Seventeen of 17 O149:H10 strains that were tested possessed the OI-48 homolog whereas 24 of 24 O149:H43 strains lacked this OI. Transposon insertions in lipB or guaA genes in strain Ro8 eliminated urease activity while insertions in the caiF gene increased urease activity. When the O149 ure operon was cloned on a high copy number plasmid, urease expression was increased approximately 11-fold in Ro8 and 83-fold in O157 strain EDL933 compared with that in the wild type Ro8. The O149 urease activity was expressed despite the presence of the same premature stop codon in ureD that is present in ure+ O157:H7 strains that are urease-negative. The ure operon in Ro8 consists of 4 893 nucleotides with 99% identity with the ure operons in EHEC O157:H7 strains EDL933 and Sakai, and is part of a GI similar to GI-48 of strain EDL933. This OI, designated OI-48149 , is inserted in the serX tRNA gene in strain Ro8 and contains genes for urease, tellurite resistance, iha and an AIDA-I-like adhesin. The presence of a homolog of the O157:H7 OI-48 in highly virulent O149 porcine ETEC suggests that this OI may contribute to establishment of the bacteria in the intestine.  相似文献   

19.
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   

20.
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   

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