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1.
为了探讨牛源产志贺毒素大肠杆菌（Shiga toxin-producing Escherichia coli,STEC）分离株在毒力基因分布和遗传进化方面与人源EHEC O157菌株之间的关系,本试验选择收集来自江苏某奶牛场的STEC菌株18株以及人源、羊源、猪源、禽源STEC参考菌株9株,参照美国疾病预防控制中心PulseNet推荐的方法,运用XbaⅠ酶进行酶切并完成脉冲肠凝胶电泳（PFGE）分型和聚类分析;同时对部分STEC菌株进行毒力基因检测。结果表明,经毒力基因检测,不同来源的O157菌株毒力基因分布不尽相同,其中牛源STEC O157与参考株EHEC O157∶H7（EDL933W）的基因排谱最为相近;牛源STEC O18和O26的基因排谱与参考株EHEC O157∶H7（EDL933W）类似,但存在部分基因的缺失。对27株不同来源的STEC分离株进行PFGE,产生了22种不同的酶切图谱。总体来看,不同来源的STEC Dice相似性系数在72%~100%之间。牛源O157分离株与猪源及禽源O157菌株的相似度偏低,而与两株人源O157分离株的相似度偏高,Dice相似性系数在83%~95%之间,牛源O26（克隆群Ⅶ、Ⅷ）与人源O157的相似性系数 > 82%。显然,从牛群中分离到的部分STEC菌株与人源EHEC O157具有较近的遗传进化关系。  相似文献   

2.
This study was aimed to understand the relationship of virulence gene distribution and genetic evolution between cattle originated Shiga toxin-producing Escherichia coli (STEC) and human originated enterohaemorrhagic Escherichia coli (EHEC) O157. This experiment collected 18 strains STEC in a dairy farm from Jiangsu province and 9 STEC reference strains (human, sheep, swine and avian), according to the method of U.S. Centers for Disease Prevention and Control Center (PulseNet), using the XbaⅠ enzyme digestion and pulsed field gel electrophoresis (PFGE) analysis, virulence genes were detected in some STEC isolates. The virulence gene distribution of O157 from different origin was remarkably different. The cattle originated STEC O157 and the human originated EHEC O157:H7 (EDL933W) had the most similar virulence gene distribution. In contrast, virulence genes were lack in cattle STEC O18 and O26, even though the cattle STEC O18 and O26 had the similar genotype as human EHEC O157:H7 (EDL933W). PFGE of Xba Ⅰ digested chromosomal DNA from 27 isolates of STEC exhibited 22 profiles. In general,the Dice coefficients of different originated STEC ranged from 72% to 100%.Cattle STEC O157 had a high similarity with two strains of human originated EHEC O157, while a low similarity was demonstrated between cattle STEC O157 and STEC O157 of swine and avian. The Dice coefficients of the cattle STEC O157 and the two strains of human EHEC O157 ranged from 83% to 95%. The Dice coefficients of cattle STEC O26 (Ⅶ,Ⅷ) and the two strains of human EHEC O157 were more than 82%. Therefore, it was concluded that the cattle STEC O157 and human EHEC O157 had a closer relationship in terms of virulence gene distribution and in genetic evolution.  相似文献   

3.
The goal of this study was to isolate and characterize phages that might be used in prevention and treatment of porcine post-weaning diarrhea due to O149 enterotoxigenic E. coli (ETEC). Serotype O149:H10:F4 was especially targeted because this is the dominant ETEC serotype. Mixtures of 10 strains of O149:H10:F4 ETEC and of 10 O149:H43:F4 ETEC were used as hosts for isolation of phages in sewage from 38 Ontario pig farms. Six phages (GJ1-GJ6) that lysed O149:H10:F4 ETEC and three (GJ7-GJ9) that lysed O149:H43:F4 ETEC were isolated. All phages produced large, clear plaques. All nine phages had necks and contractile tails and therefore belonged to the Myoviridae. Their estimated genome sizes were 48.3-50.7kb and their restriction enzyme fragments suggested that they were closely related. Phages GJ1-GJ6 lysed 99-100% of 85 O149:H10:F4 ETEC, 0-12% of 42 O149:H43:F4 ETEC, 3-35% of 37 non-O149 porcine ETEC, and 6-68% of the 72 strains of the ECOR collection. Phages GJ7-GJ9 lysed 86-98% of the O149:H43:F4 ETEC, 2-53% of the O149:H10:F4 ETEC, and 24-41% of the non-O149 porcine ETEC. Titres of the nine phages were unaffected by exposure for 16h to pH 5-9. Among phages GJ1-GJ6, resistance of O149:H10:F4 ETEC to one phage was generally not accompanied by resistance to other phages. It is concluded that the nine phages are suitable candidates for prophylaxis and therapy of porcine post-weaning diarrhea due to O149 ETEC.  相似文献   

4.
为拓宽噬菌体宿主谱,本研究通过将产肠毒素大肠杆菌(Enterotoxigenic Escherichia coli,ETEC)特异性噬菌体v B_Eco M_JS09与肠出血性大肠杆菌(Enterohemorrhagic Escherichia coli,EHEC)O157∶H7细菌进行多轮共培养,筛选到了6株能够同时裂解ETEC和EHEC O157∶H7的噬菌体,并多次传代和宿主谱鉴定,选择其中1株噬菌体Bp47-12鉴定其生物学特性。双层琼脂平板试验结果表明,噬菌体Bp47-12在平板上均呈现出了典型的裂解性噬菌体特征,空斑透亮,边缘整齐清晰,无晕环噬菌斑;宿主谱鉴定结果表明,ETEC和EHEC O157∶H7菌株均对噬菌体Bp47-12敏感,实现了噬菌体在ETEC和EHEC O157∶H7菌株之间的交叉裂解反应,拓宽了亲本噬菌体JS09的宿主谱;噬菌体Bp47-12能够耐受60℃左右高温,在p H值3~9时效价稳定;最佳感染复数为1;潜伏期为30 min,爆发期为70 min,平均爆发量分别为15;体外裂解试验结果表明,在5 h之内噬菌体Bp47-12能够有效裂解ETEC和EHEC O157∶H7菌株,OD600值下降约0.66;吸附曲线结果表明,在25 min之内,效价为105 PFU/mL的噬菌体Bp47-12能够完全吸附到宿主菌表面。本研究具有潜在的应用价值,也为拓宽裂解性噬菌体宿主谱和应用噬菌体提供了科学依据。  相似文献   

5.
为了研究重构融合蛋白Eae-Stx1/2B免疫特性及对出血性大肠杆菌感染的免疫保护作用,进行了细胞粘附抑制试验和免疫保护试验。结果证明Eae-Stx1/2B融合蛋白免疫血清在体外能降低出血性大肠杆菌对HEp-2细胞的粘附作用,这一特性在出血性大肠杆菌疫苗设计中具有重要价值。以纯化的融合蛋白Eae-Stx1/2B为抗原对小鼠进行腹腔注射免疫和滴鼻免疫,ELISA检测结果显示,2次免疫后7 d,免疫组抗Eae-Stx1/2B融合蛋白和抗出血性大肠杆菌O157血清IgG抗体显著高于未免疫组;用出血性大肠杆菌O157强毒株EDL933攻击免疫小鼠,免疫组小鼠排菌时间显著缩短,免疫组小鼠存活率均高于未免疫组,免疫组小鼠体质量恢复增长较快。上述试验结果表明,Eae-Stx1/2B融合蛋白对出血性大肠杆菌感染有保护作用。  相似文献   

6.
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   

7.
Long polar fimbriae (Lpf) are recently discovered adhesins and increasingly important genetic markers of pathogenic Escherichia coli strains. The presence and genotype diversity of Lpf operons was screened in a collection of 97 Escherichia coli O157 strains representing different pathotypes, isolated from healthy cattle (n = 43) and human patients (n = 54) in several countries. Individual structural genes of Lpf were scanned by PCR, and allelic variants were detected with a recently developed typing scheme. Ninety-five strains carried at least one whole Lpf operon (genes lpfABCD and/or lpfABCDE). The 64 enterohaemorrhagic (EHEC) and 24 enteropathogenic (EPEC) strains all carried two Lpf operons, allele 3 of lpfA1 and allele 2 of lpfA2, a combination characteristic of the O157:H7/NM serotype. Out of the 9 bovine atypical (AT; stx-, eae-) strains, 7 carried one complete Lpf operon, allele 1 of lpfA2. The atypical strains belonged to main phylogenetic groups A and B1, while the EHEC and EPEC strains were from group D. Lpf variants carried by the 72 strains of the Escherichia coli Reference Collection (ECOR) were determined with the same typing scheme. Alleles were detected in 25 strains, of which 6 were found negative for the respective Lpf operons in earlier studies. The marker value of the Lpf allelic combination for the O157:H7/NM serotype was confirmed, and further evidence was given for the presence of at least two different genetic lineages of atypical bovine E. coli O157 strains.  相似文献   

8.
These experiments determined the ability of Escherichia coli O157:H7 to colonize and persist in pigs simultaneously inoculated with other pathogenic E. coli strains. Three-months-old pigs were inoculated with a mixture of five E. coli strains. The mixture included two Shiga toxigenic E. coli (STEC) O157:H7 strains, two enterotoxigenic E. coli (ETEC) strains and one enteropathogenic E. coli (EPEC) strain. A high dose mixture with all five strains at 10(10)CFU/animal (CFU: colony forming units) and a low dose mixture with the STEC strains at 10(7)CFU and the EPEC and ETEC strains remaining at 10(10)CFU were used. The STEC strains persisted in the alimentary tracts of some pigs at 2 months post-inoculation, following inoculation with both the high and low dose mixtures. When all strains were given at 10(10)CFU (high dose) the STEC strains persisted in greater numbers and in more pigs than did the other E. coli strains. The results demonstrated that persistent colonization (> or =2 months) by E. coli O157:H7 can occur in pigs. These findings were similar to those reported from sheep inoculated with the same mixture of E. coli strains. The results are consistent with reports suggesting that pigs have the potential to be reservoir hosts for STEC O157:H7.  相似文献   

9.
Escherichia (E.) coli serotype O157:H7 is a globally distributed human enteropathogen and is comprised of microorganisms with closely related genotypes. The main reservoir for this group is bovine bowels, and infection mainly occurs after ingestion of contaminated water and food. Virulence genetic markers of 28 O157:H7 strains were investigated and multilocus enzyme electrophoresis (MLEE) was used to evaluate the clonal structure. O157:H7 strains from several countries were isolated from food, human and bovine feces. According to MLEE, O157:H7 strains clustered into two main clonal groups designated A and B. Subcluster A1 included 82% of the O157:H7 strains exhibiting identical MLEE pattern. Most enterohemorrhagic E. coli (EHEC) O157:H7 strains from Brazil and Argentina were in the same MLEE subgroup. Bovine and food strains carried virulence genes associated with EHEC pathogenicity in humans.  相似文献   

10.
Besides the well-known O157:H7 clone causing enterohaemorrhagic colitis and haemolytic uraemic syndrome in Europe, Japan and North America, the number of Escherichia coli isolates with non-motile (NM) phenotype has considerably increased. We supposed that spontaneous antibiotic resistance mutation could cause this phenotypic change. To model our hypothesis we isolated rifampicin--(Rif) and ampicillin--(Amp) resistant mutants from E. coli O157:H7 prototype strains 7785 and EDL933. Among Rifr mutants we could isolate strains with no or reduced motility, while the Ampr mutants became hypermotile. The biochemical profile of the mutants had not changed but phage sensitivity and generation time of the mutants were altered. Among the representative strains we did not find polymorphism with Southern blot analysis and no polymorphism was found in the fliC gene of the mutants. The described characteristics have proven to be stable. In a mice virulence assay by intravenous infections the virulence of the derivatives was also found to be changed. In summary, we found that the antibiotic-resistant phenotype in E. coli O157:H7 was coexpressed with several other phenotypic changes including motility and virulence. It can be assumed that expression of the involved phenotypes may be under the influence of a common regulatory cascade. Further work is needed to identify the components and mechanism of this regulatory system.  相似文献   

11.
The aims of the study were to determine the prevalence of enterohemorrhagic Escherichia coli O157:H7 (EHEC O157) and other Shiga toxin-producing E. coli (STEC) in feces of white veal calves in an operation in Ontario, to evaluate exposure of the calves to EHEC O157, and to investigate the milk replacer diet and antimicrobial resistance as factors that might influence the prevalence of EHEC O157. Feces from three cohorts of 20-21 calves were collected weekly for 20 weeks and processed for isolation of EHEC O157:H7 and detection of STEC by an ELISA. Exposure to EHEC O157 was also investigated by measuring IgG and IgM antibodies to the O157 lipopolysaccharide (O157 Ab) in sera by ELISA. The prevalences of EHEC O157 were 0.17% of 1151 fecal samples and 3.2% of 62 calves, and for STEC were 68% of 1005 fecal samples and 100% of 62 calves. Seroconversion to active IgG and IgM O157 Ab responses in some calves was not associated with isolation of EHEC O157. The milk replacer contained low levels of antibodies to EHEC antigens and without antimicrobial drugs, it did not inhibit the growth of EHEC O157 in vitro. Two E. coli O157:H7 that were isolated were totally drug sensitive whereas 60 commensal E. coli isolates that were examined were highly resistant. Antibodies in milk replacer that might be protective in vivo, and susceptibility to antimicrobial agents in the milk replacer may contribute to the low prevalence of EHEC O157 in white veal calves.  相似文献   

12.
The outcome of experimental intestinal infections with enterotoxigenic Escherichia coli (ETEC) is dependent on several factors. An important factor is adhesion of the challenge strain to the intestinal mucosa. The test for susceptibility towards ETEC adhesion has so far been made by an intestinal adhesion test made after slaughter of piglets. However, in an experimental infection study with the purpose to obtain diarrhoeic piglets, it would be an advantage to test for susceptibility prior to experimentation. The Mucin 4 gene on porcine chromosome 13 has been proposed as a candidate gene for the production of the specific ETEC F4ab/ac receptor, and a DNA marker-based test has been developed to allow genotyping for ETEC F4ab/ac resistance/susceptibility [J?rgensen, C.B., Cirera, S., Archibald, A.L., Anderson, L., Fredholm, M., Edfors-Lilja, I., 2004. Porcine polymorphisms and methods for detecting them. International application published under the patent cooperation treaty (PCT). PCT/DK2003/000807 or WO2004/048606-A2]. The aim of this study was to test an experimental model for ETEC O149:F4ac-induced diarrhoea in piglets, selected for susceptibility towards ETEC O149:F4ac adhesion prior to experimentation using a DNA marker-based test. Sixty-two healthy 25-32 days old recently weaned Danish crossbred piglets were used. All piglets were tested prior to experimentation for susceptibility or resistance towards ETEC O149:F4ac adhesion. Thirty-nine piglets, both susceptible and resistant, were oro-gastric intubated with 10(9)CFU of ETEC O149:F4ac and 23 age-matched piglets, both susceptible and resistant, were used as non-infected controls. Of susceptible piglets, challenged with ETEC O149:F4ac, 74% had ETEC O149:F4ac-associated diarrhoea first day after first challenge, which were significantly higher relatively to the resistant and challenged piglets where 20% had diarrhoea (p=0.04). This study suggests a model for experimental ETEC induced diarrhoea.  相似文献   

13.
Little is known of the association of enterohemorrhagic Escherichia coli O157:H7/NM (EHEC O157) with disease in naturally infected calves, although cattle have been known as a major source for EHEC O157 outbreaks in humans. In this study, we investigated the occurrence of EHEC O157 in calves associated with/without diarrhoea to examine if EHEC O157 is involved in calf diarrhoea and to characterize the isolates. Four hundred and ninety eight diarrhoeic and non-diarrhoeic young calves from 115 different farms were examined. Of 244 diarrhoeic calves, 24 (9.8%) were positive for EHEC O157, and of 254 non-diarrhoeic calves, 7 (2.8%) were positive. EHEC O157 was recovered from 12/76 (15.79%) of diarrhoeic calves less than 2-week-old, and no EHEC O157 was detected in this age group of non-diarrhoeic calves. This implicates EHEC O157 as a possible cause of the disease in naturally infected neonatal calves. The occurrence of EHEC O157 was relatively lower in the older calves (aged older than 8 weeks) and no significant difference was found in the occurrence rates between these diarrhoeic and non-diarrhoeic calves. PCR analysis of virulence markers revealed that the isolates carried various virulence genes such as Ehly, eae, stx1 and stx2, which underlines the potential importance of these attributes for the infection, colonization and possible pathogenesis of calf diarrhoea.  相似文献   

14.
Enterohaemorrhagic Escherichia coli (EHEC) infections in humans are an important public health concern and are commonly acquired via contact with ruminant faeces. Cattle are a key control point however cross-protective vaccines for the control of EHEC in the bovine reservoir do not yet exist. The EHEC serogroups that are predominantly associated with human infection in Europe and North America are O157 and O26. Intimin and EHEC factor for adherence (Efa-1) play important roles in intestinal colonisation of cattle by EHEC and are thus attractive candidates for the development of subunit vaccines. Immunisation of calves with the cell-binding domain of intimin subtypes beta or gamma via the intramuscular route induced antigen-specific serum IgG1 and, in some cases salivary IgA responses, but did not reduce the magnitude or duration of faecal excretion of EHEC O26:H- (Int(280)-beta) or EHEC O157:H7 (Int(280)-gamma) upon subsequent experimental challenge. Similarly, immunisation of calves via the intramuscular route with the truncated Efa-1 protein (Efa-1') from EHEC O157:H7 or a mixture of the amino-terminal and central thirds of the full-length protein (Efa-1-N and M) did not protect against intestinal colonisation by EHEC O157:H7 (Efa-1') or EHEC O26:H- (Efa-1-N and M) despite the induction of humoral immunity. A portion of the serum IgG1 elicited by the truncated recombinant antigens in calves was confirmed to recognise native protein exposed on the bacterial surface. Calves immunised with a mixture of Int(280)-gamma and Efa-1' or an EHEC O157:H7 bacterin via the intramuscular route then boosted via the intranasal route with the same antigens using cholera toxin B subunit as an adjuvant were also not protected against intestinal colonisation by EHEC O157:H7. These studies highlight the need for further studies to develop and test novel vaccines or treatments for control of this important foodborne pathogen.  相似文献   

15.
The contribution of urease activity to the pathogenesis of Actinobacillus pleuropneumoniae was investigated using 2 different urease-negative transposon mutants of the virulent serotype 1 strain, CM5 Nalr. One mutant, cbiK::Tn10, is deficient in the uptake of nickel, a cofactor required for urease activity. The other mutant, ureG::Tn10, is unable to produce active urease due to mutation of the urease accessory gene, ureG. In aerosol challenge experiments, pigs developed acute pleuropneumonia following exposure to high doses (10(6) cfu/mL) of the parental strain, CM5 Nalr, and to the cbiK::Tn10 mutant. When low dose (10(3) cfu/mL) challenges were used, neither urease-negative mutant was able to establish infection, whereas the parental strain was able to colonize and cause lesions consistent with acute pleuropneumonia in 8 of the 20 pigs challenged. These findings suggest that urease activity may be needed for A. pleuropneumoniae to establish infection in the respiratory tract of pigs.  相似文献   

16.
Two strains of E. coli O139:K12 (B):H1 were compared in vitro and in the intestinal environment. Both strains colonized the small intestines of experimentally inoculated pigs and exhibited in vivo a similar relationship to the microvillus border as enterotoxigenic E. coli (ETEC). Strain 107/86 grown on blood agar expressed numerous long flexible non-haemagglutinating fimbriae which were antigenically distinct from the known fimbriae of porcine ETEC. It adhered in vitro to porcine enterocyte brush border fragments. Strain 124/76 grown on blood agar was devoid of fimbriae and did not adhere to brush border fragments. However, fimbriae morphologically and antigenically indistinguishable from those of strain 107/86 were detected in the intestinal environment by direct immunofluorescence and by immuno electron microscopy.  相似文献   

17.
The prevalence of enterohaemorrhagic Escherichia coli (EHEC) O157 in poultry is considered minimal compared with other species, especially ruminants. However, deliberate inoculation studies have shown that poultry are readily and persistently infected by this organism but that the mechanism of colonisation is independent of intimin, a recognised factor in host-EHEC interactions in mammalian species, and may be dependent upon flagella. Few strains of EHEC O157 have been tested in poultry and here 1-day-old and 6-week-old chicks were inoculated with seven non-toxigenic E. coli O157 strains in separate experiments. Persistence was measured semi-quantitatively by bacteriological assessment of E. coli O157 cultured from cloacal swabs (shedding score). In the 1-day-old chick model that was monitored for 43 days, all seven strains established well after inoculation. In the 6-week-old chicken model, one strain established and gave consistently high shedding for the duration of the experiment (156 days). Whereas of the remaining six strains, two persisted for 113 days, two persisted for 43 days, one persisted for 22 days and one strain was never detected.  相似文献   

18.
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   

19.
Hemolytic uremic syndrome (HUS) is caused by enterohemorrhagic E. coli (EHEC) belonging to a few serovars embracing strains of O26, O103, O111, O118, O145 and O157 serogroup, respectively. In own investigations 3.791 food specimen of animal origin were investigated by use of an enzyme-immuno-assay (EIA) and the polymerase chain reaction (PCR). All E. coli isolates (n = 459) of food as well as isolates from cattle feces (n = 440), from HUS patients (n = 50) and asymptomatic human carriers (n = 16) were investigated by means of the PCR using primer pairs for verocytotoxin genes (vtx1, vtx2, vtx2c, vtx2d, vtx2e), the E. coli attaching und effacing gene (eae), the enterohemolysin-gene (ehlyA) and the vt2 transporter protein-gene (ile X tRNA). Differences were found in respect to the eae- and the ile X tRNA genes, which could be detected in significantly higher ratios in the isolates from patients and human carriers. Furthermore vtx2d strains were exclusively analyzed to each 25% in food and cattle strains. In six food samples pathogenic strains of serovar O157 were detected whereas some of the cattle strains were estimated to belong to EHEC serovars O26:H11, O118:H- and O157:H7. The own data support the thesis that the risk for human beings is affiliated to a great extent by direct contact with ruminants, followed by person-to-person transmission. Regarding the epidemiological data the thesis that each VTEC strain ist potentially an EHEC strain can not longer be substantiated.  相似文献   

20.
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   

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