首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 93 毫秒
1.
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   

2.
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   

3.
AIMS: To serotype a subset of Shiga toxin-producing Escherichia coli (STEC) isolates from cattle and sheep to determine whether any corresponding serotypes have been implicated in human diarrhoeal disease, both in New Zealand and worldwide, and to examine the distribution of STEC and enteropathogenic Escherichia coli (EPEC) amongst cattle (calves, heifers and dairy) and sheep (lambs, rams and ewes), to assess whether carriage of identified bacterial genotypes may be associated with a particular age of animal. METHODS: Recto-anal mucosal swabs (RAMS) were taken from 91 calves, 24 heifers and 72 dairy cattle, and 46 lambs, 50 ewes and 36 rams, from four sites in the Manawatu and Rangitikei regions of New Zealand. Strains of E. coli selected from primary isolation plates were subjected to a multiplex polymerase chain reaction (PCR), to determine the presence of Shiga toxin genes (stx1 and stx2) and the E. coli attaching and effacing gene (eae). RESULTS: Overall, 186/319 (58.3%) animals sampled were positive for stx1, stx2, or eae isolates. More sheep (43.9%) were stx1-positive than cattle (2.7%; p = 0.036), and amongst sheep more lambs and ewes were stx1-positive than rams (p = 0.036). Amongst cattle, more calves and heifers were eae-positive than dairy cows (p = 0.030). Two or more different STEC were isolated from at least 28 (9%) animals (three cattle and 25 sheep), based on their stx/eae genotype. Enterohaemolysin genes were found in 39/51 (76%) isolates serotyped. Twenty-one different serotypes were detected, including O5:H-, O9:H51, O26:H11, O84:H-/H2 and O149:H8 from cattle, and O26:H11, O65:H-, O75:H8, O84:H-, O91:H-, O128:H2 and O174:H8 from sheep; O84:H-, O26:H11, O5:H-, O91:H- and O128:H2 serotypes have been associated with human disease. CONCLUSIONS: If nationally representative, this study confirms that cattle and sheep in New Zealand may be a major reservoir of STEC serotypes that have been recognised as causative agents of diarrhoeal disease in humans. Distribution of STEC and EPEC in cattle and sheep indicates that direct contact with, in particular, calves or their faeces, or exposure to environments cross contaminated with ruminant faeces, may represent an increased risk factor for human disease in New Zealand.  相似文献   

4.
Thirty-one shiga toxin-producing (STEC) and 6 enteropathogenic Escherichia coli (EPEC) were isolated from 87 raw yak milk and 63 'churpi' samples. Of 18 stx(1) positive isolates (48.6%), 14 carried stx(1c) (77.7%). Subtyping of 28 stx(2) positive isolates (75.7%) revealed the presence of stx(2c) (9, 32.1%), stx(2d) (3, 10.7%), stx(2e) (1, 3.57%) and stx(2f) (3, 10.7%) variants. Furthermore, intimin (eaeA), enterohaemolysin (ehxA), autoagglutinating adhesin (saa), iha (adherence conferring protein), efa1 (EHEC factor for adherence), bundle forming pilli (bfpA) and toxB (type III secreted protein encoded on LEE Island, similar to toxin B of Clostridium difficile) genes were detected in 14, 16, 12, 4, 3, 2 and 2 isolates, respectively. Univariate and multivariate analysis depicted that both stx(1) and stx(2) or their variants were more likely to occur in isolates from Arunachal Pradesh (p<0.04) rather than Sikkim. Dendogram constructed on the basis of RAPD and ERIC PCR profile distributed the STEC and EPEC isolates in separate clusters irrespective of their sources and serotypes. The STEC and EPEC isolates exhibited resistance against erythromycin, amikacin, azithromycin, amoxicillin, ampicillin+cloxacillin, cephalothin, furazolidone, gentamicin, kanamycin, streptomycin and tetracycline. This is the first ever report on occurrence and characterization of STEC and EPEC isolated from yak milk and milk products.  相似文献   

5.
AIM: To genotype Escherichia coli cultured from the faeces of healthy cattle and sheep in the lower North Island, in order to investigate the possible role of ruminants as a reservoir for Shiga toxin-producing E. coli (STEC) in New Zealand. METHODS: A total of 952 strains of E. coli were isolated on selective media, from faecal swabs from 319 animals (187 cattle and 132 sheep) from four sites in the Manawatu and Rangitikei regions of New Zealand. A multiplex polymerase chain reaction (PCR) was used to genotype the E. coli isolates, using amplification of Shiga toxin genes (stx1 and stx2) and the E. coli attaching and effacing gene (eae). RESULTS: Isolates of E. coli were cultured from swabs from 178/187 (95.2%) cattle and all 132 (100%) sheep. Ninety-nine (10.4%) of the isolates were stx1 only, 83 (8.7%) stx2 only, 33 (3.5%) stx1 and stx2, 23 (2.4%) stx1 and eae, one (0.1%) stx2 and eae, and 115 (12.1%) were eae only. Overall, 51 (27.3%) cattle and 87 (65.9%) sheep were stx-positive, whereas 69 (36.9%) cattle and 36 (27.3%) sheep were eae-positive. CONCLUSIONS: Both healthy cattle and sheep are asymptomatic reservoirs of STEC in New Zealand. Direct contact with cattle and sheep or consumption of water or foodstuffs contaminated with cattle of sheep faeces may represent a significant source of infection for humans.  相似文献   

6.
A total of 50 Escherichia coli strains isolated in a Libyan hospital (20 from children with diarrhoea and 30 from healthy children) were investigated for their pathotypes and virulence traits. Altogether nine eae-positive (enteropathogenic E. coli, EPEC) and nine aggR-positive (entero-aggregative E. coli, EAEC) strains were identified. Significantly (P=0.001) more EPEC strains were identified from diarrhoeal patients (n=8) than from healthy controls (n=1), while six EAEC strains were identified from diarrhoeal and three from healthy children. Typical (eae(+), EAF(+), bfp(+)) EPEC strains (n=6) belonged to classical EPEC serogroups O55, O114, O127 and showed localized adherence on Hela cells. EAEC strains revealed genetic heterogeneity but uniformly adhered to HeLa cultures in an entero-aggregative adherence pattern. Antibiotic resistance frequently, characterized the strains. Sixty-eight percentage of the strains were resistant against at least one antibiotic and 30% harbored a class 1 integron independently of their clinical background. This is the first report from North Africa demonstrating the significance of EPEC and EAEC.  相似文献   

7.
DNA-DNA hybridization, cultured cell lines, and transmission electron microscopy were used to study pathogenicity traits of 64 Escherichia coli isolated from apparently healthy chickens from 18 small-scale farms in Thika District, Kenya. A total of 39 (60.9%) isolates hybridized with the eae gene probe for enteropathogenic E. coli (EPEC) whereas another 16 (25%) hybridized with the lt and st gene probes and were categorized as enterotoxigenic E. coli. Electron microscopic examination of the eae probe-positive E. coli cultures with the HT-2919A cell line confirmed that they were able to attach intimately and produced effacement typical of EPEC. In addition, negative stain electron microscopy showed that the EPEC strains produced pili that have previously been associated with increased virulence of E. coli infections in chickens. This study has also demonstrated that apparently healthy chickens may carry enteropathogenic E. coli strains.  相似文献   

8.
Bovine faecal samples were collected during June-December 1997 at 14 major abattoirs slaughtering cattle in Finland. Escherichia coli O157 was isolated from 19 of the 1448 samples (1.31%) after enrichment and immunomagnetic separation (IMS). The positive faecal isolates originated from 16 farms and eight abattoirs. The occurrence of E. coli O157 was highest in July (8/204; 3.92%) and September (6/244; 2.46%). No E. coli O157 was detected in November and December, nor from the faecal samples from the northernmost region where cattle density is low. All of the isolates carried the eae gene and showed the enterohaemolytic phenotype. All except one were motile and had the flagella antigen H7. Seventeen of the isolates were positive for stx(2) gene and one carried both the stx(1) and stx(2) genes. Of the 17 isolates with stx genes, 16 were verocytotoxin-positive in a reversed passive latex agglutination test after polymyxin extraction but only eight without extraction. The isolates belonged to 10 different pulsed-field gel electrophoresis (PFGE) patterns. The most common PFGE pattern (1.42) was detected in eight isolates (42.1%). Four PFGE patterns (1.1; 1.6; 1.12; 1.14) were identical with those isolated from humans in Finland, suggesting that at least some human E. coli O157 infections may be of bovine origin.  相似文献   

9.
A longitudinal study (cohort study) elaborating 1,224 rectal swabs from 221 calves aging between 1 and 12 weeks was conducted on 11 dairy farms (i) to ascertain associations between diarrhea and shedding of diarrheagenic E. coli and (ii) to facilitate the zoonotic potential assessment of E. coli strains shed by young calves. Calves were screened weekly by PCR of swab cultures for shedding of enterotoxigenic E coli [ETEC; by detection of heat stable (est) and heat labile enterotoxin genes (elt)], diffusely adhering E. coli [DAEC; diffuse adhesion (daa)], typical enteropathogenic E. coli [EPEC; bundle-forming pili (bfpA) and intimin (eae)] as well as enterohemorrhagic E. coli [EHEC, intimin (eae) and Shiga toxin (stx)]. In addition, EHEC-hemolysin- (Hly(EHEC)) and alpha-hemolysin- (alpha-Hly) producing E. coli were detected by inoculation of blood agar plates. Within the 221 calves, prevalences were 69.7% (25.2% of the 1,224 samples) for Hly(EHEC)-producing E. coli, 55.3% (19.3%) for eae, and 18.2% (4.5%) for stx. E. coli strains exhibiting an alpha-Hly phenotype were detected in 66.5% of the calves and 21.9% of fecal samples. The est gene was detectable in 31.7% of the calves from only 9 of 11 herds and in 7.8% of the samples. Calves shedding DAEC or typical EPEC were not identified. The detection frequency of virulence traits significantly depended on the calves' age and shedding dynamics differed between the traits. A significant correlation between calf diarrhea and shedding of EHEC virulence traits was determined for several postnatal periods (1 week: Hly(EHEC); 1st & 10th week: eae; 4th week stx). Shedding of ETEC (est) was associated with diarrhea in newborn calves (1st week) only. Hly(EHEC)- and alpha-Hly-producing E. coli were shed significantly more frequently by diarrheic calves in 1st and 8th week of life, respectively. The knowledge gained in this study highlights the high prevalence of zoonotic E. coli already in calves.The age-dependent shedding dynamic of the various E. coli pathovars has to be considered regarding prophylaxis as well as planning intervention studies, both for calves and humans.  相似文献   

10.
OBJECTIVE: To determine the prevalence and characteristics of attaching and effacing Escherichia coli (AEEC) in diarrheic and healthy small ruminants. ANIMALS: 502 lambs and kids with diarrhea and 511 healthy sheep and goats. PROCEDURE: Fecal samples from diarrheic and healthy sheep and goats were screened for the eae gene. In addition, E coli isolates with positive results for the eae gene (E coli eae+) were analyzed for the espB gene, production of verotoxins (VT), and serogroup. RESULTS: A significantly higher prevalence of healthy lambs and kids were infected with AEEC, compared with diarrheic lambs and kids and healthy adult sheep and goats. Some differences in the characteristics of E coli eae strains isolated from diarrheic and healthy animals were detected. Thus, the espB gene was detected more frequently among E coli eae+ strains isolated from healthy animals than in those isolated from diarrheic animals, and VT production was only detected in E coli eae+ strains isolated from healthy lambs and kids. The E coli eae+ isolates belonged to several O serogroups. However, 17 of 40 (42.5%) isolates from diarrheic lambs and only 4 of 168 (2.4%) isolates from healthy sheep belonged to serogroup 026. CONCLUSIONS AND CLINICAL RELEVANCE: Our results suggest that E coli eae+ 026 strains may play a role in diarrheal disease in lambs, whereas E coli eae+ strains that also had VT production and eae+ strains that had positive results for the espB gene did not appear to be associated with diarrhea in small ruminants.  相似文献   

11.
Strains of Escherichia coli (n = 390) isolated from 132 healthy, 4-8-week old calves, were tested by polymerase chain reaction (PCR) for the eae (intimin) gene and shiga toxin genes (stx1 and stx2). All strains were also analysed for F5, F17 and F41 fimbriae and for the heat-labile (LT) and heat-stable (STI and STII) genetic markers. Overall, the eae gene was detected in 84 (21.5%) of the strains tested. Only 21 (5.4%) isolates were positive for stx1 (18 strains) or stx2 (three strains); nine of the stx1-positive isolates also possessed the eae gene. A high percentage (29.2%) of the isolates tested expressed F17 but no enterotoxin genes were detected. None of the eae- or stx-positive strains belonged to the O157 serogroup.  相似文献   

12.
《Veterinary microbiology》1997,54(2):145-153
Nineteen Escherichia coli strains belonging to enteropathogenic (EPEC) serogroups were isolated from calves with diarrhea in Paraná State, Brazil, and studied for virulence markers associated with EPEC or enterohemorrhagic E. coli (EHEC). The 19 isolates belonged to 12 serotypes with isolates of O26:H11, O119:H25 and O114:H− being the most prevalent. Localized adherence (LA) was demonstrated for 37% of the isolates, consisting of all four O26:H11, both O114:H− and one O114:H40 isolates. All the LA strains were positive in the fluorescent-actin staining (FAS) test and possessed attaching-effacing E. coli (eae) sequences, but only O114 strains hybridized with the EPEC adherence factor (EAF) probe. None of the strains produced Shiga-like toxins (Verotoxin). Only the O26:H11 strains hybridized with the EHEC plasmid specific (CVD419) probe and were enterohemolytic, properties associated with EHEC strains. This investigation demonstrates that among the bovine strains isolated only those of serogroup O114 behaved as typical EPEC.  相似文献   

13.
Escherichia coli isolates from calves were investigated by multiplex PCR assays for the presence of genes encoding K99, F41, F17-related fimbriae, heat-stabile enterotoxin a (STa), intimin (eae) and Shiga toxins (stx1 and stx2). A total of 120 E. coli isolates, 75 isolated from diarrhoeic or septicemic calves and 45 from clinically healthy calves aged between 1 day and 2 months were tested. Each isolate was obtained from different calves in different herds. Among the isolates from diseased animals, 12 (16%) isolates from 1- to 7-day-old diarrhoeic calves were detected as enterotoxigenic E. coli which possessed K99, F41 and STa in combination; F17-related fimbriae genes were detected in 33 (44%) isolates and they were found in combination with K99 + F41 + STa in two isolates. Of 120 isolates, 16 carried eae, eight stx1 and five stx2 genes alone or in combination. None of the eae- or stx-positive strains was identified as O157:H7. However, results indicate that calves may be carrier of Shiga toxin-producing E. coli which have potential as a human pathogen. Antimicrobial susceptibility of 75 isolates from diseased calves was determined by agar disk diffusion method for 14 antimicrobial agents. In 77.3% of the isolates, multiresistance was detected. Higher resistance rates were detected for cephalothin (72%), tetracycline (69.3%), kanamycin (69.3%), ampicillin (65.3%), nalidixic acid (53.3%), trimethoprim-sulphamethoxazole (52%) and enrofloxacin (41.3%), respectively. No resistance was found for ceftiofur and cefoxitin.  相似文献   

14.
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   

15.
The purpose of this study was to determine the presence of stx genes in avian pathogenic Escherichia coli (APEC). We examined 97 APEC isolates: 34 from lesions of avian cellulitis, 31 from avian septicemia, 13 from swollen head syndrome (SHS) in chickens, and 19 from diseased turkeys. We also examined five isolates from the feces of healthy chickens. All 102 E. coli isolates were tested for the presence of stx genes by PCR amplification and by colony blots using probes specific for stx1 and stx2. Fifty-three percent (52) of the 97 APEC carried stx gene sequences: one isolate carried stx2 sequences, two carried both stx1 and stx2 sequences, and the remaining 49 isolates carried only stx1 sequences. Twenty-six isolates were positive by both hybridization and PCR amplification, 10 were positive by PCR only, and 16 were positive by hybridization only. All the stx-positive isolates were negative by PCR for the eae and E-hlyA genes. The five isolates from healthy chickens were all negative for stx. All 13 SHS isolates were positive for the stx1 gene and had low titres for cytotoxicity in the Vero cell assay (VCA). Other stx-positive isolates were negative in the VCA. The stx1 gene from one SHS E. coli isolate was cloned and sequenced and shown to be identical to that of the stx gene of Shigella dysenteriae. The observations indicate that stx1 gene sequences are widespread among APEC but that cytotoxicity on Vero cells is uncommon.  相似文献   

16.
A total of 178 Escherichia coli isolates from diarrheic and healthy rabbits in the S?o Paulo State (Brazil) were serobiotyped and investigated by PCR for the presence of virulence genes. Among the 90 (50.6%) isolates which possessed the eae gene, 74 were from diarrheic animals and all but one encoded intimin beta. Sixty five (72.2%) of the eae+ isolates had insertion of the locus of enterocyte effacement locus in the pheU locus, 11 (12.2%) in the selC and 14 (15.6%) did not insert in either of these loci. All isolates were negative for genes of the E. coli enterotoxins, Stx1, Stx2, CNF1, CNF2 and EHEC hemolysin. The O132:H2 serotype was dominant, being present in 63 isolates (70%) of the 90 eae+ isolates, and 57 of the 63 isolates of this serotype belonged to biotype 30. PCR detected the gene for AF/R2 fimbriae in 75 (83.3%) of the 90 eae+ isolates. Adherence to HeLa cells was best detected following 6h incubation and a positive fluorescence actin staining (FAS) test was given by 52 isolates. These data show that isolates of E. coli associated with diarrhea in rabbits in Brazil possess the genotype and phenotype typically associated with rabbit enteropathogenic E. coli (EPEC). We conclude that EPEC that possess the eae gene are a common cause of diarrhea in Brazilian rabbit farms and that the pathogenic eae+ AF/R2+ isolates of O132:H2:B30 serobiotype are especially predominant.  相似文献   

17.
Escherichia coli isolates recovered from 182 fecal specimens from dogs up to five months old from the cities of S?o Paulo and Campinas, SP, Brazil, were examined by polymerase chain reaction (PCR) for several virulence factors and properties. The eae gene was found in 23 isolates of E. coli from 22 dogs, 19 of 146 (13%) from dogs with diarrhea and 3 of 36 (8.3%) from dogs with no diarrhea. Two different eae+ isolates were recovered from one dog with diarrhea. Isolates from two dogs with diarrhea harbored the bfpA gene, and none of the isolates possessed genes for enterotoxins, the EAF plasmid or Shiga toxins. PCR showed that, among the 23 isolates, eight were positive for beta intimin, six for gamma, two for, one for alpha, one for kappa, and five showed no amplification with any of the nine pairs of specific intimin primers used. PCR also showed that the LEE (locus of enterocyte effacement) was inserted in selC in four isolates, likely in pheU in seven isolates, and in undetermined sites in twelve isolates. Fifteen isolates adhered to HEp-2 cells and were fluorescence actin staining (FAS) positive. The predominant adherence pattern was the localized adherence-like (LAL) pattern. The eae-positive isolates belonged to a wide diversity of serotypes, including O111:H25, O119:H2 and O142:H6, which are serotypes that are common among human EPEC. These results confirmed the presence of EPEC in dogs (DEPEC) with and without diarrhea. The virulence factors found in these strains were similar to those in human EPEC, leading to the possibility that EPEC may move back and forth among human and canine populations.  相似文献   

18.
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   

19.
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   

20.
Enteropathogenic Escherichia coli (EPEC) that are known to cause severe diarrhoea in children and young rabbits are well characterized, but there are few reports on the serotypes and intimin (eae) types of EPEC in weaned pigs. Based on detection of the eae gene by PCR and by DNA-hybridisation with LEE specific gene probes, 20 intestinal and 17 faecal eae(+) strains from diarrhoeal (164) and non-diarrhoeal (57) weaned pigs from 13 Hungarian farms, representing 12.8% of diarrhoeal and 14.0% of non-diarrhoeal pigs, were identified. The dominant serotype was O123:H11 (40%) among intestinal, and O108:H9 (23%) among faecal strains. The majority (85%) of the intestinal strains possessed eae-beta and 10% carried eae-gamma gene. In contrast, significantly (p<0.025) fewer faecal strains (53%) harboured the eae-beta gene, and 23% were eae-gamma positive. In vitro adhesion tests of intestinal and faecal eae(+) strains indicated adhesion of 20/37 of the strains to PK15 (porcine kidney) cells while only 3/37 strains adhered to HeLa cells. The ultrastructure of intimate bacterial attachment of representative porcine eae(+) strains to PK15 cells showed no pedestal formation, in contrast to the human EPEC (O127:H5, eae-alpha) strain. In conclusion, the data do not demonstrate a significant role for the eae(+)E. coli in porcine post-weaning diarrhoea, but provide new information on a dominant porcine serotype (O123:H11, eae-beta), and on differences of serotypes and intimin types of porcine eae(+) strains according to their site of isolation. Furthermore there was an indication that the PK15 cell line could be used as a model to study in vitro adherence of eae(+)E. coli of some human and porcine origin.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号