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1.
Cephalexin is a first generation cephalosporin commonly used in dogs for treatment of pyoderma. The objective of this study was to evaluate the in vivo effects of cephalexin on selection of Escherichia coli resistant to extended-spectrum cephalosporins. A cohort study was conducted on 13 dogs presenting clinical signs of pyoderma and treated with cephalexin and 22 healthy dogs that had not been treated with antibiotics during the previous six months. Selective plating of faeces on MacConkey agar plates containing cefotaxime (CTX) yielded growth of CTX-resistant E. coli for eight of the 13 treated dogs (62%), whereas no growth was observed for any of the control dogs (Fisher exact test, P<0.001). PCR and sequence analysis identified bla(CMY-2) in all eight dogs. PCR-based replicon typing and restriction fragment length polymorphism (RFLP) of E. coli transformants revealed location of bla(CMY-2) on indistinguishable IncI1 plasmids in five of the eight dogs. One representative of these five epidemiologically related IncI1 plasmids was further characterized as sequence type (ST2) by plasmid multilocus sequence typing (pMLST). E. coli from the remaining three dogs harboured bla(CMY-2) on distinct plasmids with non-typeable replicons. A single isolate was classified as an extraintestinal pathogenic E. coli (ExPEC) due to the presence of iutA, papC and sfa/foc. The results provide a strong indication that cephalexin selects for E. coli producing plasmid-borne CMY-2 β-lactamase. The isolation of a specific IncI1 plasmid carrying bla(CMY-2) from five epidemiologically unrelated dogs suggests that cephalexin use may contribute to the spread of this plasmid lineage among Danish dogs.  相似文献   

2.
Isolates of extended-spectrum cephalosporin (ESC)-resistant Salmonella enterica serovar Typhimurium obtained from two different farms in Fukushima Prefecture, Japan, in 2007 were characterized in order to determine the genetic basis of resistance. ESC resistance in the two isolates was mediated by an AmpC β-lactamase encoded by the bla(CMY-2) gene, which is located in a large self-transmissible plasmid in each isolate. The sizes of the bla(CMY-2)-carrying plasmids were different. The replicon types of the plasmids were I1-Iγ and A/C. The results of macrorestriction analysis and phage typing suggest a close relationship between both isolates. This is the first report of ESC-resistant S. Typhimurium isolated from cattle in Japan.  相似文献   

3.
Hospital-based infection control in veterinary medicine is emerging and the role of the environment in hospital-acquired infections (HAI) in veterinary hospitals is largely unknown. This study was initiated to determine the recovery of Escherichia coli and selected veterinary and zoonotic pathogens from the environments of 101 community veterinary hospitals. The proportion of hospitals with positive environmental swabs were: E. coli--92%, Clostridium difficile--58%, methicillin-resistant Staphylococcus aureus (MRSA)--9%, CMY-2 producing E. coli--9%, methicillin-resistant Staphylococcus pseudintermedius--7%, and Salmonella--2%. Vancomycin-resistant Enterococcus spp., canine parvovirus, and feline calicivirus were not isolated. Prevalence of antimicrobial resistance in E. coli isolates was low. Important potential veterinary and human pathogens were recovered including Canadian epidemic strains MRSA-2 and MRSA-5, and C. difficile ribotype 027. There is an environmental reservoir of pathogens in veterinary hospitals; therefore, additional studies are required to characterize risk factors associated with HAI in companion animals, including the role of the environment.  相似文献   

4.
Multidrug-resistant Salmonella enterica serovar Typhimurium (S. Typhimurium) isolates with four different antimicrobial resistance patterns obtained from a beef cattle farm were characterized to determine their clonality. Macrorestriction analysis of genomic DNA revealed that these four isolates are closely related to each other and can be classified as a newly emerged pulsed-field gel electrophoresis type among cattle: cluster VII. Three of the four isolates showed resistance to extended-spectrum cephalosporins (ESCs), and this resistance was mediated by AmpC β-lactamase encoded by the bla(CMY-2) gene in a 190-kbp IncA/C plasmid. Results of restriction analysis and IncA/C backbone PCR suggest that the three 190-kbp plasmids are identical and that a 70-kbp IncA/C plasmid of the ESC-susceptible isolate is derived from the 190-kbp plasmid by a deletion event. Three isolates harboured a virulence-resistance plasmid (165 or 180 kbp), and restriction analysis revealed that these plasmids were identical or closely related to each other. These results suggest that the four S. Typhimurium cluster VII isolates originate from a common ancestor that probably invaded the farm prior to the salmonellosis outbreak. Antimicrobial resistance patterns may not necessarily reflect the relationships of the isolates.  相似文献   

5.
To evaluate the diversity of extended-spectrum β-lactamases (ESBL) genes among food-producing animals, 48 isolates of ESBL-producing Escherichia coli isolates were obtained from rectal samples of broilers, layers, beef cattle and pigs, at the slaughterhouse level. ESBL-carrying E. coli were isolated from 60.0% of individual broiler rectal samples, 5.9% of layers, 12.5% of beef cattle and 3% of pigs. One ESBL-producing Klebsiella pneumoniae was isolated from a broiler. The ESBL-positive E. coli isolates from broilers harbored various ESBL genes: bla (SHV-12), bla(CTX-M-2), bla(CTX-M-14), bla(CTX-M-15) and bla(CTX-M-44). The plasmid DNAs were analyzed by restriction patterns. Homogeneous band patterns were yielded in those of K. pneumoniae and E. coli isolates harboring the bla(CTX-M-2) gene from different farms. No genetic relation between the 2 CTX-M-14 ESBL-producing strains was found by pulsed-field gel electrophoresis, although 2 plasmids in these strains, obtained from different broiler farms, were similar to each other. This study provides evidence that the proliferation of CTX-M-producing E. coli is due to the growth of indigenous CTX-M-producing strains and the possible emergence of strains that acquired CTX-M genes by horizontal transfer in different broiler farms. CTX-M-producing coliforms in broilers should be controlled due to the critical importance of cephalosporins and the zoonotic potential of ESBL-producing bacteria.  相似文献   

6.
Resistance of Salmonella to extended-spectrum cephalosporins (ESCs) is being reported with increasing frequency. In humans, infections with Salmonella resistant to ESCs threaten the efficacy of ceftriaxone, the drug of choice for treating salmonellosis in children. To determine the occurrence of resistance to ESCs, we examined 8426 strains isolated from food-producing animals in Canada in 1994–99 for reduced susceptibility or resistance to ceftriaxone. Of the 8 such strains identified (7 from turkeys and 1 from cattle), 5 had reduced susceptibility, and 3 were resistant; 2 were isolated in 1995, 1 was isolated in each of 1996 and 1997, and 4 were isolated in 1999. Isoelectric focusing showed that all 8 isolates produced a β-lactamase with a pI ≥ 9. The strains were resistant to cefoxitin and not inhibited by clavulanic acid. Primers specific for the Citrobacter freundii blaAmpC gene produced the expected product in the polymerase chain reaction. DNA sequencing showed that all isolates possessed the blaCMY-2 gene. Plasmid DNA from all 8 isolates transformed Escherichia coli DH10B, whereas only 1 isolate transferred blaCMY-2 conjugally. All transformants and the transconjugant were resistant to ampicillin, cefoxitin, ceftiofur, cephalothin, streptomycin, sulfisoxazole, and tetracycline. Southern blots of plasmids from the isolates, the transformants, and the transconjugant showed that blaCMY-2 was located on similar-sized plasmids (60 or 90 MDa) in the transformants and the transconjugant. In the S. Typhimurium DT104 and S. Ohio isolates, the floSt gene was found on the same plasmid. Class 1 integrons with the aadB gene cassette were detected in the S. Bredeney isolates but not in their transformants or the transconjugant. Pulsed-field gel electrophoresis and plasmid profiles indicated that both clonal dispersion and horizontal transfer of blaCMY-2 may have caused dissemination of the resistance determinant.  相似文献   

7.
The aim of the study was to compare the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli bovine isolates on a conventional dairy cattle farm with high consumption of parenteral and intramammary cephalosporins (farm A) and on an organic dairy farm with no cephalosporin use (farm B). ESBL-producing E. coli were isolated from rectal swabs and milk filters by selective cultivation on MacConkey agar with cefotaxime (2mg/l). ESBL genes were identified by polymerase chain reaction (PCR) and sequencing, and the genetic diversity of the isolates was determined by XbaI pulsed field gel electrophoresis (PFGE). Conjugative transfer, incompatibility group, and restriction fragment length polymorphism (RFLP) profiles of the ESBL-carrying plasmids were studied. Higher prevalence (39%, n(rectal samples in cows)=309) of CTX-M-1-producing E. coli isolates was found on farm A compared to farm B (<1%, n(rectal samples in cows)=154; 0%, n(rectal samples in calves)=46). Using PFGE, the isolates from farm A were divided into nine pulsotypes. In all ESBL-positive isolates, the bla(CTX-M-1) gene was carried on 40 kb IncN conjugative plasmids of three related HincII restriction profiles. Horizontal gene transfer through transmission of IncN plasmids harboring bla(CTX-M-1) as well as clonal dissemination of a particular clone seems to be involved in dissemination of CTX-M-1-producing E. coli isolates in cows on the farm using cephalosporins in treating bacterial infections. The study demonstrates a possible role of cephalosporin use in the widespread occurrence of CTX-M-1-producing E. coli on the conventional dairy cattle farm compared to the organic farm.  相似文献   

8.
在１１５株猪大肠杆菌耐药性监测的基础上,提取耐药类型最普遍的５株耐药菌的质粒进行质粒指纹图谱分析。结果表明：同一来源、耐药类型相同的菌株有相似的质粒图谱,来源不同者,酶切图谱有提示出它们之间的同源性,说明质粒指纹图谱可作为流行病学调查的工具。  相似文献   

9.
Nasal swabs were collected at three time points from 2378 calves in four feedlots and cultured for Histophilus somni to assess genetic relatedness and tetracycline resistance. The proportions of animals carrying tetracycline resistant isolates were 0.32% at arrival, 14.82% at interim, and 0.80% at exit. The 606 H. somni isolates recovered were compared by pulsed-field gel electrophoresis (PFGE), screened for the presence of plasmids, and assessed for the tetracycline resistance genes tet(A), tet(B), tet(C), tet(E), tet(G), tet(H), tet(K), tet(L), tet(M) and tet(O) using multiplex polymerase chain reaction. Most of the isolates (98.6%) belonged to one of seven PFGE clusters (A-G) of closely related profiles with 77.7% of the isolates belonging to clusters C and D. Clusters A, B and E were associated with a higher proportion of tetracycline susceptible isolates. Genetic diversity of the isolates was highest at entry in the feedlot and lowest after the period when the animals received in-feed chlortetracycline (interim samples). Clusters A and E were more prominently represented at exit from the feedlot than other clusters. All resistant strains harboured the gene tet(H) while no other tetracycline resistance genes and no plasmids were detected with the methodology employed. It appears that genetic variability in H. somni in Alberta feedlots is low, dissemination likely occurs by clonal expansion, and resistance to tetracyclines is mediated by the tet(H) encoded efflux pump. Pulsotypes associated with tetracycline susceptible strains appear more common at exit suggesting that the in-feed oxytetracycline included throughout the feeding period is not sufficient to exert selective pressure for resistant strains.  相似文献   

10.
The aim of the present study was to contribute to the knowledge on extended-spectrum beta-lactamases (ESBL's), AmpC beta-lactamases and integrons in Enterobacteriaceae isolated from horses, which is still limited. The susceptibility of 1581 clinical isolates from animals to ceftiofur was tested. Most of these isolates (n=1347) originated from horses. Seven ceftiofur-resistant equine isolates (four Escherichia coli and three Klebsiella pneumoniae) were identified and all seven were multidrug-resistant. These isolates were further studied for the presence of ESBL's, AmpC beta-lactamases and class 1 integrons. The potential for the horizontal transfer of resistance genes among these clinical isolates was also studied. ESBL-type resistance genes were found in five isolates, AmpC-type genes in one isolates and integrons in six isolates. Nucleotide sequence analysis revealed that the isolates carried the bla(CTX-M-1), bla(CMY-2), bla(TEM-1) and/or bla(SHV-1) genes. This is the first report describing the in vitro conjugal transfer of the bla(CTX-M-1) genes from a clinical E. coli isolate to Salmonella isolates. Gene cassettes encoding resistance to aminoglycosides (aadA1, aadA2 and aadA5), and trimethoprim (dfrA1, drfA12 and dfrA17) were found on the integrons present in the isolates. The cassette arrays of the dfrA17-aadA5 and dfrA1-aadA1 genes in the two integrons of a single E. coli isolate have not yet been described before. To our knowledge this is the first report on ESBL's and AmpC beta-lactamases in equine E. coli and Klebsiella isolates.  相似文献   

11.
Faecal samples of healthy dogs (n=39) and cats (n=36) obtained in Northern Portugal were seeded on Levine agar plates, and two Escherichia coli isolates per sample were recovered (78 of dogs and 66 of cats). The susceptibility to 16 antimicrobial agents was tested in this series of 144 E. coli isolates. Almost 20% of them showed tetracycline resistance and 12 and 15% presented ampicillin or streptomycin resistance, respectively. The percentage of resistance to the other antimicrobial agents was in all cases below 4%, and no resistant isolates were detected for ceftazidime, imipenem, cefoxitin or amikacin. Two isolates (from one dog) showed cefotaxime-resistance and harboured both the CTX-M-1 and OXA-30 beta-lactamases. A bla(TEM) gene was detected in 12 of 17 ampicillin-resistant isolates, the aac(3)-II gene in the three gentamicin-resistant isolates, aadA in 7 of 22 streptomycin-resistant isolates, and tet(A) and/or tet(B) gene in all 28 tetracycline-resistant isolates. The gene encoding class 1 integrase was detected in six E. coli isolates, including the four trimethoprim-sulfamethoxazole-resistant isolates and those two harbouring CTX-M-1 and OXA-30 beta-lactamases; different gene cassette arrangements were identified: dfrA1+aadA1 (two isolates), dfrA12+orfF+aadA2 (two isolates) and bla(OXA30)+aadA1 (two isolates). One amino acid change in GyrA protein (Ser83Leu or Asp87Tyr) was detected in four nalidixic acid-resistant and ciprofloxacin-susceptible isolates and two amino acid changes in GyrA (Ser83Leu+Asp87Asn) and one in ParC (Ser80Ile) were identified in one nalidixic acid- and ciprofloxacin-resistant isolate. Faecal E. coli isolates of healthy pets could be a reservoir of antimicrobial resistance genes.  相似文献   

12.
The presence of fimbrial adhesin F18 is frequently found in enterotoxigenic Escherichia coli (ETEC) and verotoxigenic E. coli (VTEC) strains responsible for diarrhoea and oedema disease of weaned pigs. The F18 adhesin occurs in two antigenic variants: F18ab is characteristic of VTEC while F18ac is more typical for ETEC. F18 encoding plasmids of 17 phenotypically characterized porcine E. coli isolates (10 ETEC, 6 VTEC and 1 ETEC/VTEC) were tested with a DNA probe for F18 fimbrial adhesin and with replicon probes for the RepFIa, RepFIb and for the RepFIc family of basic replicons. In all the cases, the F18 probe hybridized to only one plasmid band of size higher than 42MDa. All F18 plasmids were determined to be unireplicon plasmids belonging to the RepFIc replicon family of the F incompatibility complex. There was no difference between F18ac plasmids of ETEC and F18ab plasmids of VTEC strains in terms of replicon type or subtype. However, the size of F18ab plasmids of the VTEC strains varied between 42 and 98MDa, in contrast to F18ac plasmids of ETEC strains (constantly approximately 98MDa).  相似文献   

13.
The objective of this longitudinal study was to investigate the occurrence and genetic background of faecal Escherichia coli resistant to cefotaxime (CTX) in horses receiving broad-spectrum antimicrobial prophylaxis after admission to a veterinary teaching hospital. The ten horses enrolled in the study were treated with cefquinome either alone (n=4) or in combination with metronidazole (n=3) or other antimicrobial agents (n=3). CTX-resistant coliforms in faeces collected before, during and after treatment were quantified on selective MacConkey agar supplemented with CTX, and a colony isolated randomly from each positive sample was characterized by pulsed-field gel electrophoresis, and by PCR detection and sequencing of bla(TEM), bla(SHV), bla(CTX-M) and bla(CMY). All horses were negative for CTX-resistant coliforms at admission but became positive within the first three days of treatment. The average faecal densities of CTX-resistant coliforms increased significantly following antimicrobial prophylaxis (P<0.001). Genetic characterization of 29 faecal isolates revealed that this effect was due to proliferation of E. coli producing either CTX-M-1 (n=28) or CTX-M-14 (n=1). Five CTX-M-1 isolates produced additional β-lactamases (TEM-1, CMY-34 and the novel variant CMY-53). Shedding of CTX-M-producing E. coli appeared intermittent in four horses and persisted two weeks after antimicrobial treatments in five of six patients tested after discharge from hospital. Nosocomial transmission was suggested by finding five identical CTX-M-1-producing E. coli pulsotypes in multiple horses. The originality of the study lies in the unanticipated high frequency and genetic diversity of CTX-M-producing E. coli observed in the faecal flora of hospitalized patients receiving broad-spectrum antimicrobial prophylaxis.  相似文献   

14.
This study aims to determine the presence of extended-spectrum (ESBL) and plasmidic class C beta-lactamase-producing Enterobacteriaceae in poultry, pig and rabbit farms of Catalonia (Spain). PFGE typing showed a low clonal relationship among strains carrying these mechanisms of resistance. Ninety-three percent of them were resistant to two or more of the non-beta-lactam antimicrobials tested and harboured ESBL and plasmidic class C beta-lactamases. Greater diversity of these enzymes was found in strains from poultry farms, the CTX-M-9 family, especially CTX-M-14, with CMY-2 being the most frequent. The isolation of TEM-52 and SHV-2-producing Escherichia coli strains from these animal farms is noteworthy. In contrast, 73% of the strains from pig farms had CTX-M-1, and neither the CMY-type nor CTX-M-9 family enzyme was found. Likewise, it is the first time that CTX-M-1 and SHV-5 encoding strains have been isolated in pigs. On the other hand, in rabbit farms CTX-M-9 family was also the most frequent, being detected in three of a total of four strains. The last one showed a CMY-2, for the first time detected in these animals, too. In conclusion, commensal E. coli strains of food-producing animal farms are a reservoir of ESBL and plasmidic class C beta-lactamases.  相似文献   

15.
A surveillance study was undertaken to examine the population dynamics and antimicrobial resistance of Mannheimia haemolytica isolated from feedlot cattle. A total of 416 isolates were collected from the nasopharynx either upon entry or exit from two feedlots in southern Alberta, Canada. Isolates were serotyped, characterized by pulsed-field gel electrophoresis and tested for susceptibility to ten antimicrobial agents via disk diffusion. Resistant isolates were screened by PCR for select antimicrobial-resistance gene determinants. Isolates were highly diverse, with 335 unique pulsed-field profiles identified among 147 strongly related clusters (similarity ≥ 85%). Clonal spread of isolates throughout the feedlots was limited and no clear association was found between genetic relatedness of M. haemolytica and sampling event (entry or exit). Pulsed-field profiles sharing a common serotype and resistance phenotype tended to cluster together. The majority of isolates were identified as serotype 2 (74.5%) although both serotype 1 (11.9%) and 6 (12.7%) were detected. Only 9.54% of isolates exhibited antimicrobial resistance. Resistance to oxytetracycline was most prevalent (n=16), followed by ampicillin (n=10), and amoxicillin/clavulanic acid (n=7). Multi-drug resistance was observed in five isolates. The tetH gene was detected in all but two oxytetracycline resistant isolates. Other detectable resistance determinates included ermX and bla(ROB-1). In the two feedlots examined, M. haemolytica exhibited considerable genetic diversity and limited resistance to common veterinary antibiotics. Garnering further information on the linkage between genotype and phenotype should contribute toward a better understanding of the pathogenesis and dissemination of M. haemolytica in feedlots.  相似文献   

16.
The prevalence of carriage of antimicrobial-resistant (AMR) and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli was determined in 183 healthy dogs from a semi-rural community in Cheshire. Isolates were tested against a panel of antimicrobials and by PCR to detect resistance genes. In the suspected ESBL-producing isolates, the presence of bla(SHV), bla(TEM), bla(CTX-M) and bla(AmpC) genes was determined by PCR and sequencing. A total of 53 (29 per cent, 95 per cent confidence interval [CI] 22.4 to 35.5 per cent) dogs carried at least one AMR E coli isolate. Twenty-four per cent (95 per cent CI 17.9 to 30.2 per cent) of dogs carried isolates resistant to ampicillin, 19.7 per cent (95 per cent CI 13.9 to 25.4 per cent) to tetracycline and 16.9 per cent (95 per cent CI 11.5 to 22.4 per cent) to trimethoprim. A bla(TEM) gene was detected in 39 of 54 ampicillin-resistant isolates, a tet(B) gene in 12 of 45 tetracycline-resistant isolates, and a dfr gene in 22 of 33 trimethoprim-resistant isolates. Multidrug-resistant isolates were demonstrated in 15 per cent (28 of 183; 95 per cent CI 10.1 to 20.5 per cent) of dogs. Nine suspected ESBL-producing E coli were isolated, of which only one was confirmed by double disc diffusion testing. Two of these isolates carried the bla(TEM-1) gene and seven carried the bla(CMY-2) gene.  相似文献   

17.
Wang Y  He T  Han J  Wang J  Foley SL  Yang G  Wan S  Shen J  Wu C 《Veterinary microbiology》2012,159(1-2):53-59
The aim of this study is to characterize the prevalence of extended-spectrum β-lactamases (ESBLs) and plasmid-mediated quinolone resistance (PMQR) genes in Escherichia coli from captive non-human primates. A total of 206 E. coli isolates were collected from primates in six zoos in China in 2009 and their susceptibility to 10 antimicrobials were tested by broth microdilution. The susceptibility patterns of E. coli strains varied greatly among different zoos reflecting different backgrounds of antimicrobial usage. Both the ESBL-encoding genes and the PMQR genes were detected by PCR. Of the 206 strains, 65 (32%) were confirmed as phenotypic ESBL producers with bla(CTX-M) (27%, bla(CTX-M-15), n=31, bla(CTX-M-3), n=23 and bla(CTX-M-14), n=2) mainly mediating the ESBL phenotype. qnrS1 (18%, n=36) and oqxAB (15%, n=31) were the predominant PMQR genes and the prevalence of PMQR genes was much higher among phenotypic ESBL producers than that among phenotypic non-ESBL producers from any zoo. Notably, the PMQR genes qnrS1 and oqxAB and β-lactamase genes bla(TEM-1) and bla(CTX-M-3) were found together in 23 E. coli isolates in two zoos in Shanghai. PFGE analysis of these 23 isolates demonstrated nearly identical PFGE profiles (similarity matrix >97%) indicating this specific E. coli genotype was prevalent in these two zoos. To the best of our knowledge, this is the first report of these four genes coexisting in an E. coli genotype and the first report of antimicrobial resistance profiles in E. coli isolated from primates in China.  相似文献   

18.
A study was conducted in 2 feedlots in southern Alberta to identify environmental sources and management factors associated with the prevalence and transmission of Escherichia coli O157:H7. Escherichia coli O157:H7 was isolated in preslaughter pens of cattle from feces (0.8%), feedbunks (1.7%), water troughs (12%), and incoming water supplies (4.5%), but not from fresh total mixed rations. Fresh total mixed rations did not support the growth of E. coli O157:H7 and E. coli from bovine feces following experimental inoculation. Within a feedlot, the feces, water troughs, and feedbunks shared a few indistinguishable subtypes of E. coli O157:H7. A few subtypes were repeatedly isolated in the same feedlot, and the 2 feedlots shared a few indistinguishable subtypes. The prevalence of E. coli O157:H7 in water troughs of preslaughter cattle in 1 feedlot was associated with season, maximum climatic temperatures the week before sampling; total precipitation the week before sampling, and coliform and E. coli counts in the water trough.  相似文献   

19.
A feedlot trial was conducted to assess the efficacy of an Escherichia coli O157:H7 vaccine in reducing fecal shedding of E. coli O157:H7 in 218 pens of feedlot cattle in 9 feedlots in Alberta and Saskatchewan. Pens of cattle were vaccinated once at arrival processing and again at reimplanting with either the E. coli O157:H7 vaccine or a placebo. The E. coli O157:H7 vaccine included 50 microg of type III secreted proteins. Fecal samples were collected from 30 fresh manure patties within each feedlot pen at arrival processing, revaccination at reimplanting, and within 2 wk of slaughter. The mean pen prevalence of E. coli O157:H7 in feces was 5.0%; ranging in pens from 0% to 90%, and varying significantly (P < 0.001) among feedlots. There was no significant association (P > 0.20) between vaccination and pen prevalence of fecal E. coli O157:H7 following initial vaccination, at reimplanting, or prior to slaughter.  相似文献   

20.
Ten Escherichia coli O157 strains isolated from cattle and children in Poland were investigated by the use of molecular biological methods. All strains possessed the intimin and enterohaemolysin genes and harboured the genetic determinants for Stx2 toxin (five isolates), Stx1 toxin (two strains) or both (three isolates). The genetic relatedness of the strains was examined by restriction fragment length polymorphism (RFLP) of chromosomal DNA digested with Xbal and Notl. Nine closely related RFLP patterns were observed. Comparison of bovine and human E coli O157 isolates based on the analysis of Xbal and Notl digested profiles showed that all strains belonged to one genetic cluster. These results indicate that cattle must be considered as a possible source of human E coli O157 infection in Poland.  相似文献   

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