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1.
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   

2.
Shiga toxin-producing Escherichia coli (STEC), particularly O157, are major food borne pathogens. Non-O157 STEC, particularly O26, O45, O103, O111, O121, and O145, have also been recognized as a major public health concern. Unlike O157, detection procedures for non-O157 have not been fully developed. Our objective was to develop a multiplex PCR to distinguish O157 and the 'top six' non-O157 serogroups (O26, O45, O103, O111, O121, and O145) and evaluate the applicability of the multiplex PCR to detect the seven serogroups of E. coli in cattle feces. Published sequences of O-specific antigen coding genes, rfbE (O157) and wzx and wbqE-F (non-O157), were analyzed to design serogroup-specific primers. The specificity of amplifications was confirmed with 138 known STEC strains and the reaction yielded the expected amplicons for each serogroup. In feces spiked with pooled 7 STEC strains, the sensitivity of the detection was 4.1 × 10(5)CFU/g before enrichment and 2.3 × 10(2) after 6h enrichment in E. coli broth. Additionally, 216 fecal samples from cattle were collected and tested by multiplex PCR and cultural methods. The multiplex PCR revealed a high prevalence of all seven serogroups (178 [O26], 108 [O45], 149 [O103], 30 [O111], 103 [O121], 5 [O145], and 160 [O157]) of 216 samples in fecal samples. Cultural procedures identified 33.1% (53/160) and 35.5% (11/31) of PCR-positive samples for E. coli O157 and non-O157 serogroups, respectively. Samples that were culture-positive were all positive by the multiplex PCR. The multiplex PCR can be used to identify serogroups of putative STEC isolates.  相似文献   

3.
Clinically healthy domestic animals can harbour Escherichia coli O157 and other verocytotoxigenic E. coli (VTEC) strains in their faeces. Milk filters can be used to microbiologically monitor direct milk secretion and environmental contamination for these pathogens. The aim of this study was to establish baseline data on the prevalence and characteristics of VTEC organisms in lactating animals (bovine, ovine and caprine) supplying milk to the farmhouse cheese sector, with particular emphasis on serogroups O157, O111 and O26. Fifty-six bovine, 13 caprine and 5 ovine herds/flocks, the majority of which supplying milk for farmhouse cheese production, were surveyed from May 2004 to July 2005. Milk filters were analysed by immunomagnetic separation followed by PCR, on a serogroup-specific basis for E. coli O157, O26 and O111. Positive isolates were examined using a multiplex PCR protocol, for their potential to produce verocytotoxins (vt1/vt2), the haemolysin-encoding gene (hlyA) and the gene encoding attaching and effacement (eae). Five verocytotoxigenic and 22 non-virulent E. coli O157 isolates were detected. Seventeen E. coli O26 isolates were also detected, four of which were verocytotoxigenic, seven isolates contained the eae gene only and six isolates were devoid of any of the virulence factors. The VTEC O157 and O26 isolates contained the hlyA and eae genes along with the verocytotoxin genes. No E. coli O111 isolates were detected. Some of the herds were positive on more than one occasion and multiple E. coli serogroups were isolated from the same milk filter sample. Although all food products tested were VTEC negative, routine surveillance for such pathogens in raw milk/raw milk products is of public health importance. Herd-level surveillance along with subsequent risk management action may be a cost-effective component of risk reduction strategies for food production, drinking water supplies and the protection of public health.  相似文献   

4.
Lee JH 《Veterinary microbiology》2009,135(3-4):401-405
The present study was to investigate antimicrobial resistance profiles of Escherichia coli O26 and O111 from cattle and to characterize the virulence genes of the resistant isolates. This paper reports the high prevalence of antimicrobial resistant E. coli O26 and O111 from cattle. Among 37 E. coli O26 and 25 E. coli O111 isolates from the fecal specimens obtained from cattle, 26 (70%) and 15 (60%) were resistant to at least one antibiotic, respectively. Forty (98%) of the 41 resistant isolates were resistant to two or more antibiotics. Among the 22 antibiotics tested in this study, ampicillin was the most common antibiotic that the isolates were resistant to, followed by tetracycline and streptomycin. None of the isolates were resistant to fluoroquinolones, such as ciprofloxacin, ofloxacin and norfloxacin, and to ceftriaxone, amikacin and imipenem. Eighteen different resistant types among the 41 isolates were observed by the cluster analysis. The most frequent antibiotic-resistance type was ampicillin-tetracycline-streptomycin-cephalothin-sulfisoxazole-ticarcillin-kanamycin-minocycline-piperacillin-chloramphenicol, which accounted for 9 (22%) of the resistant isolates. The observation of frequent and multiple resistances to antibiotics highlights the need for their careful use if their benefits are to be preserved. PCR analysis of the EHEC virulence markers showed that 25 of the resistant E. coli O26 and O111 isolates tested positive for stx2 or both stx1 and stx2. This suggests that the majority of these isolates can cause serious diseases in humans and may complicate the future therapeutic options under development.  相似文献   

5.
Verocytotoxigenic Escherichia coli (VTEC) are highly significant zoonotic threats to public health, and have been the causative agent implicated in numerous high-profile outbreaks affecting large numbers of people. Serovar O157 is most frequently linked with human illness; however, other serovars, such as O26, O103, O111 and O145, have also been implicated. This study aimed to characterize the prevalence and virulence determinants of these five serovars in Irish dairy farm herds, and their milk. Using real-time PCR (RTi-PCR), bovine rectal faecal swabs and raw milk samples, along with milk filters, were screened for the presence of vt genes. Positive samples were then screened for the five serovars using sero-specific PCR. Serovar-positive samples were subjected to immunomagnetic separation, to isolate viable VTEC strains. These isolates were subsequently screened for four virulence factors: vt1, vt2, eaeA and hlyA. Three hundred and eighty six of the 600 rectal faecal swabs, 85 of the 117 milk-filters and 43 of the 120 bulk-tank milk samples, were positive for vt genes. From these 514 total vt-positive samples, 58 O26, 162 O103, 1 O111, 324 O145 and 26 O157 positives were detected by sero-specific RTi-PCR. Immunomagnetic separation yielded 12 O26, 26 O103, 0 O111, 19 O145 and 10 O157 isolates. Ten of these isolates contained at least one of the four virulence determinants screened for (i.e. vt1, vt2, eaeA and hlyA). Of these 10 isolates, pulsed-field gel electrophoresis showed that two of the O26 isolates from different farms were indistinguishable. Two O157 isolates were also indistinguishable. This study found serovars O103 and O145 to be the most prevalent in samples tested. Apart from the occurrence of VTEC in dairy herds, this study shows a high occurrence of vt genes in the environment, creating the possibility of horizontal gene transfer and emergence of new VTEC strains.  相似文献   

6.
牛源大肠杆菌O157：H7的分离及毒力基因鉴定   总被引：1，自引：0，他引：1  
从2个牛场采集新鲜粪便,增菌后,免疫磁珠富集,涂布筛选性培养基,挑取可疑菌落用rfbE/fliC二重PCR和血清学方法鉴定。设计毒力基因stx1、stx2、eae、hlyA和tccp相应引物,针对O157：H7对分离株进行PCR鉴定。口服攻毒链霉素处理的BALB/c小鼠明确分离株致病性。结果显示,成功分离到7株出血性大肠杆菌O157：H7,并且有1株迟缓性发酵山梨醇麦康凯培养基。毒力基因检测显示,其中6株毒力因子表型为stx1-stx2＋eae＋hlyA＋tccp＋,另有1株表现型为stx1＋stx2＋eae＋hlyA＋tccp＋,各分离株tccp基因均为阳性,但携带的重复片段数量有差异。所采集样品中肠出血性大肠杆菌O157：H7的检出率高达12%。1×1010 CFU同剂量口服接种经PBS洗涤的5株O157：H7分离株全菌,小鼠存活率有差异分别为40%,50%,60%,20%,50%,各分离株在小鼠体内排菌时间也有差异分别为攻毒后7,9,13,13,15d。  相似文献   

7.
The aims of this study were: (1) to examine whether or not enterohemorrhagic Escherichia coli O26 and O111 (EHEC O26 and O111) are involved in neonatal calf diarrhea; (2) to determine the specific age periods at which the calves are vulnerable to these organisms, and (3) to reveal the biochemical, genetic and cytotoxic characteristics of the isolates. The study investigated the occurrence of EHEC O26 and O111 in calves associated with or without diarrhea. A total of 442 diarrheic and non-diarrheic young calves from 115 different farms were examined. Of the 257 calves with diarrhea, 37 (14.4%) and 32 (12.5%) tested positive for EHEC O26 and EHEC O111, respectively. Of the 185 non-diarrheic calves, 14 (7.6%) and 11 (5.9%) tested positive for EHEC O26 and EHEC O111, respectively. EHEC O26 and O111 were recovered from 14/69 (20%) and 11/69 (16%) diarrheic calves <2-weeks-old, respectively, and no EHEC O26 and O111 were detected in the non-diarrheic claves of this age group, suggesting that EHEC O26 and O111 are possible causes of the disease in infected neonatal calves. However, there were similar rates of occurrence in the diarrheic and non-diarrheic calves in the older animals (particularly, aged >10 weeks). PCR analysis showed that the isolates carried various virulence genes such as Ehly, eae, stx1 and stx2, which highlight the potential importance of these attributes for the infection, colonization and the possible pathogenesis of calf diarrhea. Cytotoxicity analysis revealed that many of the EHEC isolates showed high cytotoxicity to Vero cells, re-emphasizing the potential for cattle being a direct source of EHEC infections in humans.  相似文献   

8.
Cattle hides are an important source of enterohaemorrhagic Escherichia coli (EHEC) carcass contamination at slaughter. Seven EHEC serogroups are adulterants in raw, non‐intact beef: EHEC O26, O45, O103, O111, O121, O145 and O157. The objective of this study was to estimate the probability for hide contamination with EHEC among US market beef cows at slaughter and to test the effects of season and geographic region on prevalence of hide contamination. Hides (n = 800) of market cows were swabbed at slaughter immediately after exsanguination, prior to hide removal. Cows were sampled from two geographically distinct beef packing plants during four seasons of 2015. Cattle source was categorized by northern or southern region. Samples were tested for EHEC by a molecular screening assay. The effects of region, season and their interaction on the probability of hide contamination by each EHEC serogroup were tested in separate multilevel multivariable logistic regression models, accounting for the random effect of clustering by plant. Statistical significance was set α = .05. Of 800 total samples, at least one EHEC was detected on 630 (79%) hides. Enterohaemorrhagic E. coli O26 was detected on 129 (16%) of all hides sampled, EHEC O45 on 437 (55%), EHEC O103 on 289 (36%), EHEC O111 on 189 (24%), EHEC O121 on 140 (18%), EHEC O145 on 171 (21%) and EHEC O157 on 89 (11%). Detection of EHEC O26 and EHEC O121 was associated with season. Season and region were associated with detecting EHEC O45 and EHEC O157. Season‐by‐region interactions were associated with the outcome of detecting EHEC O103, EHEC O111 and EHEC O145. Season, region of origin and the interaction of these factors affect hide contamination of market beef cattle at slaughter by EHEC, and each serogroup responds to these factors uniquely.  相似文献   

9.
Enterohaemorrhagic Escherichia coli (EHEC) O26:H11 have emerged as the most important non-O157:H7 EHEC, with respect to their ability to cause diarrhoea and the haemolytic uraemic syndrome (HUS). HUS is a leading cause of acute renal failure in children, and is mainly caused by EHEC expressing Shiga toxins (Stx) 1 and/or 2. Since 1996, EHEC O26, which produce Stx2 only and appear to have enhanced virulence, have been increasingly isolated from HUS patients in Germany. In contrast, EHEC O26 found in cattle predominantly produce Stx1 as the sole Stx. Additional potential virulence factors of EHEC O26 include cytolysins (EHEC hemolysin), serine proteases (EspP), lymphotoxins (Efal) and adhesins (intimin). The genes encoding the virulence factors are located within pathogenicity islands (eae, efa1), bacteriophages (stx) or plasmids (EHEC-hlyA, espP). In addition, EHEC O26 possess, in contrast to other EHEC, the "high pathogenicity island" (HPI), which is also present in pathogenic Yersiniae.This island contains genes involved in the biosynthesis, regulation and transport of the siderophore yersiniabactin. Comparative genomic analyses between EHEC O26 and non-pathogenic E. coli, as well as investigations of mechanisms involved in the transfer of virulence genes, provide a deeper insight into the evolution of EHEC O26.These studies demonstrate how horizontal transfer of virulence genes, even from distantly related organisms, can lead in brief intervals to the rise of a highly virulent clone within a particular E. coli serotype.The classical bacteriological methods are no longer sufficient to determine the risk posed by EHEC O26. However, knowledge of the complete virulence profiles of these pathogens and understanding their stepwise evolution form a foundation for developing new strategies to prevent human infections and new methods for their laboratory diagnosis.  相似文献   

10.
A total of 136 Shiga toxin-producing Escherichia coli (STEC) isolated during a longitudinal survey of three Australian dairy farms were examined to determine their virulence factors, serotype and genomic relationships. This study aimed to assess the potential of these STEC to cause disease in humans and to analyse the on-farm ecology of STEC. Virulence factors (stx, eae, ehxA) were used as determinants of potential to be enterohaemorrhagic E. coli (EHEC) and were examined using polymerase chain reaction (PCR). Among the cattle groups tested, calves, both before and during weaning, shed the most putative EHEC and were the main source of serotypes commonly associated with human disease. E. coli O157:H7 and E. coli O26:H11 represented 9.4 and 7.8% of cattle STEC isolates respectively, with other putative EHEC serotypes reported for the first time from cattle. Based on serotype and virulence factors, 20% of STEC were putative EHEC. Pulsed-field gel electrophoresis (PFGE) was used to compare the genomic profiles of STEC from dairy farms. Isolates common to cattle and the farm environment were identified. Multiple strains of STEC with high clonal turnover were detected in the faeces of cattle, and isolates appeared to be specific to individual farms. To fully assess the pre-slaughter EHEC risk factors on-farm, examination of STEC virulence is as important as determination of STEC prevalence.  相似文献   

11.
Faecal samples were collected from 573 slaughtered cattle aged between three and 24 months in seven abattoirs. After enrichment (mTSB with novobiocin), samples were screened by real‐time PCR first for stx and if positive, tested for the top‐five Shiga toxin‐producing Escherichia coli (STEC) serogroups using PCR assays targeting genes specific for serogroups O26, O103, O111, O145 and O157. Of 563 samples with available results, 74.1% tested positive for stx genes. Amongst them, the serogroups O145, O103, O26, O157 and O111 were detected in 41.9%, 25.9%, 23.9%, 7.8% and 0.8%, respectively. From 95 O26, 166 O145 and 30 O157 PCR‐positive samples, 17 O26, 28 O145 and 12 O157 strains were isolated by colony hybridization after immunomagnetic separation. The 17 O26 strains were eae‐positive, but only nine strains harboured stx (eight possessing stx1 and one stx2). Of the 28 O145 strains, ten were eae‐positive including four harbouring stx1 or stx2, whereas 18 were negative for stx and eae. Five of the 12 O157 strains harboured stx2 and eae, did not ferment sorbitol, and were identified as STEC O157:H7/H?. The other seven O157 strains were negative for stx and eae or positive only for eae. Shiga toxin genes and the top‐five STEC serogroups were frequently found in young Swiss cattle at slaughter, but success rates for strain isolation were low and only few strains showed a virulence pattern of human pathogenic STEC.  相似文献   

12.
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   

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.
Domestic animals belonging to seven different species (cattle, sheep, dogs, cats, pigs, chicken and goats) were investigated as natural reservoirs for attaching and effacing Escherichia coli (AEEC). For this, 2165 E. coli strains from faeces of 803 animals were examined for the presence of the intimin -(eae) gene as a characteristic of AEEC strains. Ten percent of the animals were found to excrete AEEC, most frequently found in sheep (19.2%) and pigs (17.6), followed by cattle (10.4%), dogs (7.2%), cats (6.5%) and poultry (2.3%). The 97 AEEC strains from animals were grouped into 44 serotypes. Only four E. coli serotypes (O2:H8, O26:[H11], O109:[H25] and O145:[H28] were found in more than one animal host species. AEEC O26:[H11] strains were most frequently isolated (13.4%) being present in cattle, poultry, pigs and sheep. A search for virulence markers associated with enterohemorrhagic E. coli (EHEC) revealed Shiga-toxin genes in three (3.1%) AEEC strains from sheep. Bundle forming pili genes as a trait of typical enteropathogenic E. coli (EPEC) were detected in four (4.1%) strains from dogs and cats. The remaining 90 AEEC strains were classified as atypical EPEC. Typing of intimin genes revealed intimin beta being present in 51.5% of the strains, followed by intimins theta (23.7%), epsilon (6.2%), kappa (5.2%), zeta (5.2%), alpha, eta and iota (each 1.0%). Our data indicate that domestic animals and pets constitute an important natural reservoir of AEEC strains, and some of these (O26:[H11], O103:H2, O128:H2, O145:[H28] and O177:[H11]) are known to occur as pathogens in humans.  相似文献   

15.
This study identified potential virulence markers in 93 eae-positive and 179 eae-negative Shiga toxin-producing Escherichia coli (STEC), isolated from a random sampling of healthy cattle in southwestern Ontario. PCR amplification was used to identify genes for enterohemorrhagic E. coli (EHEC)-hemolysin, the EAF plasmid, and bundle-forming pili (Bfp); adherence to HEp-2 cells and to bovine colonocytes, and the fluorescent actin staining (FAS) test were used to characterize interaction of the bacteria with epithelial cells. The EHEC-hemolysin sequences were detected in 98% of eae-positive isolates compared with 34% of eae-negative isolates. All isolates were negative for EAF and bfp sequences. There was 100% correlation between localized adherence (LA) to HEp-2 cells and the FAS test. Forty-eight (52%) of the eae-positive isolates were LA/FAS-positive, whereas none of the 179 eae-negative isolates was positive in either test. Among the eae-negative isolates, 20 (11%) showed diffuse adherence and 5 (2.8%) showed enteroaggregative adherence to HEp-2 cells. Seventy-three percent of the eae-positive isolates adhered to bovine colonocytes, whereas only 26% of 120 eae-negative isolates that were tested adhered. All 13 O157:H7 isolates were positive for eae and EHEC-hemolysin gene sequences, LA/FAS, and adherence to bovine colonocytes. It is concluded that possession of genes for eae and EHEC hemolysin is correlated with the serotype of STEC, that production of EHEC hemolysin was highly correlated with serotypes implicated in human disease, and that none of the potential markers that were examined can be used to predict the potential virulence of an isolate.  相似文献   

16.
The study objectives were to determine the prevalence and serotypes of non-O157 Shiga toxin-producing Escherichia coli (STEC) in pens of feedlot cattle and on corresponding beef carcasses. We collected 25 fecal samples from 84 pens in 21 Alberta feedlots and 40 carcass swabs from each preslaughter pen for analysis by culture and polymerase chain reaction (PCR). Non-O157 STEC were recovered from feces from 12 (14%) of the 84 pens and 12 (57%) of the 21 feedlots by examination of 1 E. coli isolate positive for 4-methylumbelliferyl-beta-beta-glucuronide per sample. Twelve non-O157 serotypes were detected, but 7 of the 15 STEC isolates lacked the accessory virulence genes eae and hlyA. Although 115 (7%) of the carcass broths were PCR-positive, no STEC isolates were recovered from the 1650 carcasses sampled. Our data indicate that multiple non-O157 STEC serotypes may be present in cattle feces, yet are unlikely to be recovered from the corresponding beef carcasses when 20 colonies per sample from PCR-positive broth cultures are analyzed.  相似文献   

17.
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   

18.
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   

19.
The aims of this study were to investigate the incidence of Salmonella, verocytotoxigenic Escherichia coli (VTEC)/Escherichia coli O157 and Campylobacter on four mixed farms and to characterize the isolates in terms of a range of virulence factors. Eighty-nine composite (five different samples from the same animal species combined) faecal [cattle (24), pigs (14), sheep (4), poultry (4), horses (7), deer (4), dogs (9), rodents (2) and wild birds (20)] samples, 16 composite soil samples plus 35 individual water samples were screened using culture-based, immunomagnetic separation and molecular methods. Salmonella was detected in bovine faeces, cattle and poultry house water. Salmonella serotypes/phage types included Dublin, Kiel and Typhimurium DT193, and most isolates were spvC, invA and rck positive. The pefA and rck genes were found exclusively in the non-Typhimurium strains, while Salmonella Dublin and Salmonella Kiel strains carried Salmonella genomic island I marker(s). VTEC/E. coli O157 were found in deer and dog faeces only. The E. coli O157 isolate was an enteroinvasive E. coli, while the VTEC isolate was untypable but carried the vt1, eaeA, hlyA, tir and eptD genes. This article reports the first confirmed carriage of E. coli O157 in Irish deer. Campylobacter species were not detected over the course of this study. It was concluded that [1] Salmonella, VTEC and Campylobacter have low (<5%) prevalence or are absent on the farms in this study; [2] water was an important source of bacterial pathogens; [3] both dogs and deer may act as a source of pathogenic E. coli and [4] key virulence and resistance determinants are widespread in farm Salmonella strains. This study highlights the need to control water as a source of pathogens and suggests that the domestic pets and deer should be considered in any farm risk assessment.  相似文献   

20.
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   

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