共查询到20条相似文献，搜索用时 312 毫秒
1.
Best A La Ragione RM Clifford D Cooley WA Sayers AR Woodward MJ 《Veterinary microbiology》2006,113(1-2):63-72
Isolation of Shiga-toxin (Stx) positive Escherichia coli O157:H7 from commercially grown pigs has been reported. Furthermore, experimental infection studies have demonstrated that Stx-positive E. coli O157:H7 can persist in 12-week-old experimentally orally inoculated conventional pigs for up to 2 months and that persistence was not dependent upon intimin. We have shown that the flagellum of Stx-negative E. coli O157:H7 does not have a role to play in pathogenesis in ruminant models whereas, in poultry, the flagellum of E. coli O157:H7 was important for long-term persistent infection. The contribution of the flagellum of Stx-negative E. coli O157 in the colonisation of pigs was investigated by adherence assays on a porcine (IPI-21) cell line, porcine in vitro organ culture (IVOC) and experimental oral inoculation of conventional 14-week-old pigs. E. coli O157:H7 NCTC12900nal(r) and isogenic aflagellate and intimin deficient mutants adhered equally well to IPI-21 cells. In porcine IVOC association assays, E. coli O157:H7 NCTC12900nal(r) was associated in significantly higher numbers to tissues from the caecum and the terminal rectum than other sites. The aflagellate and intimin deficient mutants significantly adhered in greater numbers to more IVOC gastrointestinal tissues than the parent. Groups of 14-week-old pigs were dosed orally with 10(10)CFU/10ml of either E. coli O157:H7 NCTC12900nal(r) or isogenic aflagellate and intimin deficient mutants and recovery of each test strain was similar. Histological analysis of pig tissues at post mortem examination revealed that E. coli O157 specifically stained bacteria were associated with the mucosa of the ascending and spiral colon. These data suggest that colonisation and persistence of Stx-negative E. coli O157:H7 in pigs, involves mechanisms that do not require the flagellum or intimin. 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.
Padola NL Sanz ME Blanco JE Blanco M Blanco J Etcheverria AI Arroyo GH Usera MA Parma AE 《Veterinary microbiology》2004,100(1-2):3-9
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
4.
5.
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
6.
Colonization of the small intestine of weaned pigs by enterotoxigenic Escherichia coli that lack known colonization factors. 总被引：2，自引：0，他引：2
Intestinal colonization of 3-week-old weaned pigs by enterotoxigenic Escherichia coli (ETEC) strains that were originally isolated from weaned pigs with fatal diarrhea and that lacked K88, K99, F41, and 987P adhesins (4P- ETEC) was studied by histologic, immunofluorescent, and electron microscopic techniques. In the first experiment, 16 principal pigs were inoculated orogastrically with ETEC strain 2134 (serogroup O157: H19) or 2171 (serogroup 0141:H4), and eight control pigs were not inoculated. In the second experiment, 24 principals were inoculated with ETEC strain 2134, and 12 controls were inoculated with a nonenterotoxigenic strain of E. coli. Principal and control pigs were necropsied at intervals from 24 to 72 hours after inoculation of principals to provide the tissues used for this report. Results from the two experiments and with both ETEC strains were similar and therefore were combined. Adhesion by 4P- ETEC was demonstrated in ileum but not in cecum or colon in 22/40 principal pigs sampled at 24 to 72 hours after orogastric inoculation. Adherent bacteria were most apparent on the intestinal villi covering Peyer's patches. Only occasional adherent bacteria were detected in ileal sections from a few (4/20) of the control pigs. Adherence by 4P- ETEC was characterized by "patches" of bacteria closely associated with the lateral surfaces and less frequently with the tips and the bases of intact villi. In most cases, the adherent bacteria were separated from epithelial cell microvilli and other bacterial cells by a 50-400-nm space. Filamentous bacterial appendages bridged this space and formed a network among adjacent bacteria.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
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
8.
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
9.
Enteropathogenic Escherichia coli (EPEC) bacteria frequently cause severe enteric diseases primarily in children and in young rabbits. Their pathogenicity for pigs has been tested by oral infection of colostrum-deprived newborn, and of severely immunosuppressed weaned pigs, but colonisation of conventional weaned pigs by porcine EPEC has not been experimentally studied. EPEC show similarities to enterohaemorrhagic E. coli (EHEC) additionally carrying shiga toxin genes integrated into the chromosome by lambdoid phages. We have demonstrated earlier that the porcine EPEC prototype strain P86-1390 (O45) could be transduced in vivo (in ligated loops of weaned pigs), by Stx2 phage derived from a human EHEC. Thus, the ability of this porcine EPEC strain to colonise conventional weaned pigs under farming conditions became a question of relevance to human health. To clarify this question, four intragastric infection experiments were performed on a total of 95 conventional weaned pigs. The EPEC P86-1390 and other well-characterised porcine EPEC strains were applied to 54 pigs, leaving 41 weaned pigs as negative controls. In three experiments moderate predispositions were applied: coinfections with enterotoxigenic E. coli (ETEC) or with low-virulence TGE coronavirus, application of fumonisin B1 with a normal therapeutic dose of dexamethasone, and the increase of soybean protein concentration in the feed. A total of 41 weaned pigs served as negative controls inoculated with a commensal porcine E. coli. Housing conditions simulated the farm environment. As an overall result, ileal segments of 18.5% of infected pigs were shown to be colonised by EPEC, while no EPEC were detected in the ilea of controls. Among predisposing factors occurring on farms, feed protein content increased by 20% (26.3% crude protein, provided by 48% soybean meal) seemed to enhance EPEC colonisation and resulted in the mobilisation of spontaneous latent EPEC/ETEC infection. The results indicate that under normal farm conditions porcine EPEC may colonise conventional weaned pigs by inducing ileal attaching effacing (AE) lesions with reasonable frequency, without clinical signs. The results also suggest that conventional weaned pigs may represent undetected reservoirs of porcine EPEC, potentially giving rise to the emergence of new types of EHEC due to natural transduction by Stx phages. 相似文献
10.
The aim of this study was to evaluate a Chemiluminescence Enzyme Immunoassay (CLIA) developed for the detection of E. coli O157:H7, using different E. coli O157 serotypes. The sensitivity and specificity of the kit were determined from the tenfold dilutions of the 24-hour broth cultures of the test strains. According to the results obtained in this trial, the sensitivity of the kit is 10(3)-10(4) cells ml-1, and it is specific for E. coli O157. Twenty-five g ground raw beef samples were prepared and inoculated with E. coli O157:H7 at different CFU g-1. The samples were incubated in 225 ml of modified E. coli broth with novobiocin (mEC + n) at 42 degrees C for 4 h and the immunoassays were performed following the instructions of the manufacturer. According to the results obtained by the CLIA test 10(1)-10(2) E. coli O157 g-1 can be detected from the sample. So this kit seems to be suitable for screening the samples before selective cultivation of E. coli O157:H7. 相似文献
11.
Serotypes,phage types and virulence genes of shiga-producing Escherichia coli isolated from sheep in Spain 总被引：3，自引：0，他引：3
Rey J Blanco JE Blanco M Mora A Dahbi G Alonso JM Hermoso M Hermoso J Alonso MP Usera MA González EA Bernárdez MI Blanco J 《Veterinary microbiology》2003,94(1):47-56
PROBLEM ADDRESSED: Shiga toxin-producing Escherichia coli (STEC), have emerged as food poisoning pathogens which can cause severe diseases in humans. OBJECTIVE: The aim of this study was to determinate the serotypes and virulence genes of STEC strains isolated from sheep in Spain, with the purpose of determining whether sheep represent a potential source of STEC pathogenic for humans. METHODS AND APPROACH: Faecal swabs obtained from 697 healthy lambs on 35 flocks in Spain during the years 2000 and 2001 were examined for STEC using phenotypic (Vero cells) and genotypic (PCR) methods. RESULTS: STEC O157:H7 strains were isolated from seven (1%) animals in six flocks, whereas non-O157 STEC strains were isolated from 246 (35%) lambs in 33 flocks. A total of 253 ovine STEC strains were identified in this study. PCR showed that 110 (43%) strains carried stx(1) genes, 10 (4%) possessed stx(2) genes and 133 (53%) both stx(1) and stx(2). Enterohaemolysin (ehxA) and intimin (eae) virulence genes were detected in 120 (47%) and in 9 (4%) of the STEC strains. STEC strains belonged to 22 O serogroups and 44 O:H serotypes. However, 70% were of one of these six serogroups (O6, O91, O117, O128, O146, O166) and 71% belonged to only nine serotypes (O6:H10, O76:H19, O91:H-, O117:H-, O128:H-, O128:H2, O146:H21, O157:H7, O166:H28). A total of 10 new O:H serotypes not previously reported in STEC strains were found in this study. Seven strains of serotype O157:H7 possessed intimin type gamma1, and two strains of serotype O156:H- had the new intimin zeta. STEC O157:H7 strains were phage types 54 (four strains), 34 (two strains) and 14 (one strain). CONCLUSIONS: This study confirms that healthy sheep are a major reservoir of STEC pathogenic for humans. However, because the eae gene is present only in a very small proportion of ovine non-O157 STEC, most ovine strains may be less pathogenic. 相似文献
12.
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
13.
Domestic farm animals represent an important reservoir of infection for Shiga toxin-producing Escherichia coli (STEC). Nevertheless the bacterial factors required to colonise these hosts are poorly defined. In this study, the prevalence of a recently described fimbrial gene cluster, lpfO113, among human and animal isolates of STEC was investigated. lpfO113 has been shown to play a role in the adherence of STEC O113:H21 to epithelial cells. Here the presence of the lpfAO113 gene (predicted to encode a major fimbrial subunit) was examined by PCR in E. coli of serogroups O157 and O26 isolated from pigs (n=38), cattle (n=10), and humans (n=9). In addition, we tested for several other genetic virulence markers including Shiga toxin (stx), intimin (eae), the translocated intimin receptor (tir), EHEC-hemolysin (ehx) and F18 fimbriae (fedA). Overall 45 of the 57 strains (79%) possessed the lpfAO113 gene as determined by the presence of a 573 bp PCR product. Moreover, there was a close correlation between the presence of the lpfAO113 marker and the absence of the eae gene. lpfAO113 was found in all of pig isolates, suggesting a possible role in colonisation of the porcine host. In addition, several E. coli strains isolated from pigs had two fimbrial gene markers, fedA and lpfAO113. lpfAO113 was not present in strains of E. coli O157:H7 as described previously. Overall these results show that lpfAO113 is widely distributed among eae-negative E. coli isolates and thus may represent an important adherence factor in this group of pathogens. 相似文献
14.
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
15.
Over a 12 month period, 588 cattle faecal samples and 147 farm environmental samples from three dairy farms in southeast Queensland were examined for the presence of Shiga-toxigenic Escherichia coli (STEC). Samples were screened for Shiga toxin gene (stx) using PCR. Samples positive for stx were filtered onto hydrophobic grid membrane filters and STEC identified and isolated using colony hybridisation with a stx-specific DNA probe. Serotyping was performed to identify serogroups commonly associated with human infection or enterohaemorrhagic Escherichia coli (EHEC). Shiga-toxigenic Escherichia coli were isolated from 16.7% of cattle faecal samples and 4.1% of environmental samples. Of cattle STEC isolates, 10.2% serotyped as E. coli O26:H11 and 11.2% serotyped as E. coli O157:H7, and the E. coli O26:H11 and E. coli O157:H7 prevalences in the cattle samples were 1.7 and 1.9%, respectively. Prevalences for STEC and EHEC in dairy cattle faeces were similar to those derived in surveys within the northern and southern hemispheres. Calves at weaning were identified as the cattle group most likely to be shedding STEC, E. coli O26 or E. coli O157. In concurrence with previous studies, it appears that cattle, and in particular 1-14-week-old weanling calves, are the primary reservoir for STEC and EHEC on the dairy farm. 相似文献
16.
S. M. Markland K. L. Shortlidge D. G. Hoover S. Yaron J. Patel A. Singh M. Sharma K. E. Kniel 《Zoonoses and public health》2013,60(8):563-571
The contamination of lettuce, spinach and basil with pathogenic E. coli has caused numerous illnesses over the past decade. E. coli O157:H7, E. coli O104:H4 and avian pathogenic E. coli (APECstx‐ and APECstx+) were inoculated on basil plants and in promix substrate using drip and overhead irrigation. When overhead inoculated with 7 log CFU/ml of each strain, E. coli populations were significantly (P = 0.03) higher on overhead‐irrigated plants than on drip‐irrigated plants. APECstx‐, E. coli O104:H4 and APECstx+ populations were recovered on plants at 3.6, 2.3 and 3.1 log CFU/g at 10 dpi (days post‐inoculation), respectively. E. coli O157:H7 was not detected on basil after 4 dpi. The persistence of E. coli O157:H7 and APECstx‐ were similar when co‐inoculated on lettuce and spinach plants. On spinach and lettuce, E. coli O157:H7 and APEC populations declined from 5.7 to 6.1 log CFU/g and 4.5 log CFU/g, to undetectable at 3 dpi and 0.6–1.6 log CFU/g at 7 dpi, respectively. The detection of low populations of APEC and E. coli O104:H4 strains 10 dpi indicates these strains may be more adapted to environmental conditions than E. coli O157:H7. This is the first reported study of E. coli O104:H4 on a produce commodity. 相似文献
17.
Ohya T Ito H 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》1999,61(10):1187-1189
Three 3-month-old Japanese Black calves were experimentally infected with Escherichia coli O157:H7 to define the magnitude (CFU/g) and duration of fecal shedding of the organism. In two of the three calves, fecal shedding of E. coli O157:H7 ceased in 5 and 9 weeks. The remaining calf continued shedding E. coli O157:H7 for more than 31 weeks, and the magnitude of the shedding ranged from 10(1) to 10(4) CFU/g of feces. The possibility is suggested that a percentage of animals naturally infected with E. coli O157:H7 on farms may become long-term shedders, transmitting the organism to other animals in the herd and to the proximate environment. 相似文献
18.
Verocytotoxin-producing Escherichia coli O157:H7 (VTEC O157:H7) was detected in two of 2446 individual faecal samples collected from pigs slaughtered at five Swedish slaughterhouses, indicating a prevalence of 0.08 per cent, with a 95 per cent confidence interval from 0 to 0.16 per cent Four Swedish VTEC O157:H7-positive farms which kept ruminants and pigs were studied by repeated faecal sampling; VTEC O157:H7 was isolated from the ruminants and pigs on all the farms and the same strains were present in the pigs and the ruminants. On one of the farms, the organism persisted in the pig population for 11 months. On all four farms, management practices which might have influenced the isolation rate in pigs were identified. A group of young VTEC O157:H7-positive pigs was moved from one of the VTEC O157:H7-positive farms to a fattening herd where there were no ruminants. The number of VTEC O157:H7-positive faecal samples decreased gradually and after nine weeks the pigs were all negative; at slaughter none of the pigs was VTEC O157:H7-positive. 相似文献
19.
L Beutin 《Veterinary research》1999,30(2-3):285-298
Certain strains of Escherichia coli behave as pathogens in dogs and cats causing gastro-intestinal and extra-intestinal diseases. Among the five known groups of diarrhoeagenic E. coli, namely enteropathogenic E. coli (EPEC), enterotoxigenic E. coli (ETEC), enteroinvasive E. coli (EIEC), shiga-toxin producing E. coli (STEC) and enteroaggregative E. coli (EAggEC), only EPEC and ETEC were clearly associated with enteric disease in young dogs. ETEC isolates from diarrhoeic dogs were found to be positive for the heat-stable enterotoxins STa and STb but negative for heat-labile enterotoxin (LT). Canine ETEC were found to be different from those of other animals and humans by their serotypes, production of alpha-haemolysin and adhesive factors and by the production of uncharacterized types of enterotoxins by some ETEC. Canine EPEC could be distinguished from EPEC of humans or other animals by their serotypes and by the eae-protein intimin which mediates intimate adherence of EPEC to intestinal mucosa cells. STEC were occasionally isolated from faeces of healthy and diarrhoeic dogs but their role in canine diarrhoea is not yet well known. EIEC and EAggEC were not reported to occur in dogs or cats. Very little is known on diarrhoegenic E. coli in cats and further epidemiological investigations on this subject are needed. Besides its role in gastro-intestinal infections, E. coli can cause infections of the urogenital tract and systemic disease in dogs and cats. Extra-intestinal pathogenic E. coli strains from dogs and cats belong to a limited number of serotypes and clonal groups and are frequently found as a part of the normal gut flora of these animals. Many of these E. coli strains carry P-fimbriae and produce alpha-haemolysin and a necrotizing cytotoxin (CNF1). Some of the frequently isolated types of extra-intestinal pathogenic E. coli from dogs, cats and humans were found to be highly genetically related but showed differences in their P-fimbrial adhesins which determine host specificity. Transmission of extra-intestinal and enteral pathogenic E. coli between dogs and humans was reported. Further research is needed, however, to determine the role of dogs and cats as transmission vectors of pathogenic E. coli strains to other animals and humans. 相似文献
20.
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