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1.
Linkages among genes for production of Escherichia coli heat-stable enterotoxin (ST), drug resistance, K99 antigen, and colicin were investigated in 2 bovine and 3 porcine strains of enterotoxigenic E coli. In conjugation experiments, all 5 isolates transferred enterotoxigenicity and the ability to produce K99; 4 of the 5 isolates also transferred antibiotic resistance markers, and 3 colicinogenic strains transmitted the ability to produce colicin. In 2 of the 3 colicin-producing strains, the genes for colicin were located along with those for K99 and ST on a single plasmid. One of these 2 strains transferred the genes for tetracycline resistance and production of both mouse-active ST (STa) and mouse-inactive ST, whereas the other transmitted the gene(s) for STa only. Transformation studies with the 3rd strain revealed that the K99 determinant resided on a 22-megadalton (Mdal)R plasmid, and that STa and colicin production were on a 65-Mdal plasmid. Analysis of the plasmids from the transformation experiments revealed that the larger plasmid was conjugative and the smaller plasmid was nonconjugative; stable cointegrate formation occurred between these 2 plasmids. Genetic information coding for the production of STa and K99 were also present on a single plasmid of approximately 80 Mdal in both noncolicinogenic strains.  相似文献   

2.
Sixty Actinobacillus pleuropneumoniae (App) strains from pigs in Taiwan were examined. Serotyping revealed that these belonged to serovars 1 (n=53), 2 (n=3), and 5 (n=4). Agar disk diffusion susceptibility testing of the isolates showed 55 (92%) were resistant to three or more antimicrobial agents. Six resistance patterns were observed. Ampicillin-chloramphenicol-flumequine-nalidixic acid-streptomycin-sulfonamide/trimethoprim-tetracycline was the most common multi-resistance pattern. Minimal inhibitory concentration of 14 antimicrobial agents was determined. The isolates were highly susceptible to ceftiofur and trimethoprim in vitro. Isolates were resistant to streptomycin, ampicillin, and nalidixic acid. All isolates were examined for the presence of plasmids using the alkaline lysis method. Forty three (72%) isolates had four plasmid bands with an approximate sizes of 3.5, 4.3, 5.8 and 6.0 kb; 12 (20%) had three bands at 3.5, 4.3 and 5.2 kb, and 5 (8%) had no plasmid bands. Antimicrobial resistance plasmids were detected in resistant strains of App. Three antimicrobial resistance plasmids were transformed into E. coli DH5 alpha. pTMY1 (4.3 kb) encoded a streptomycin kinase and a dihydropteroate synthase; pTMY2 (6.0 kb) encoded ROB-1 beta-lactamase and aminoglycoside 3'-phosphotransferase; pTMY3 (5.2 kb) encoded only ROB-1 beta-lactamase. The 4.3 kb plasmid was sequenced and consisted of 4242 bp with 42.9% GC content. The 4.3 kb plasmid DNA sequence was 98% homologous to a plasmid previously isolated from Pasteurella haemolytica.  相似文献   

3.
鸡源大肠杆菌的耐药性监测及生物学特性研究   总被引：2，自引：2，他引：0  
从山东省诸城地区6个集约化养鸡场采集50只病死鸡病料,从中分离鉴定得到32株大肠杆菌,对其进行了12种常规药敏试验,发现分离的菌株有不同程度的耐药性。对14株优势血清型菌株进行了质粒DNA提取分析,然后用Hind Ⅲ限制性内切酶对质粒进行了酶切。结果表明,质粒的得率为100%,来源相同的菌株具有相同或相似的质粒图谱,也就是说它们有共同的起源;来源不同的菌株的质粒图谱一般不同,即有不同的起源。将血清型和质粒图谱比较,结果发现,同一血清型可以有不同的质粒图谱,不同血清型可以有相似的质粒图谱,血清型与质粒图谱没有直接的联系。  相似文献   

4.
盘宝进  谢永平  杨威  苏栋 《中国畜牧兽医》2006,33(10):I0006-I0009
从广西各地病死猪器官、组织中分离到17株细菌,经细菌形态、培养特性及生化反应鉴定为大肠杆菌。作本动物回归试验、小白鼠致病性试验和溶血试验结果表明,全部为致病性大肠杆菌。血清定型鉴定结果发现,菌株血清型分布不规律。17株致病性大肠杆菌的质粒指纹图谱显示:来源于不同猪群的菌株GP20-3和GP25-1以及GP18-9和GP8-3分别具有相同的质粒图谱,说明发病猪群传染源的首发菌相同。所有菌株都含有1条大小相同的质粒带,广西流行的猪水肿病主要是由在遗传学上具有高度同源相关性的大肠杆菌的广泛流行传播所引起。菌株GP18-9和GP8-3的质粒指纹图谱相同,但它们的血清型却不一致的现象,可作为自然条件下,同一质粒在不同血清型大肠杆菌中扩散转化的一个生物学依据。  相似文献   

5.
A total of 190 Salmonella typhimurium strains encountered in different parts of India were characterized on the basis of plasmid profile, phage type and antimicrobial resistance pattern. Recent trends in the epidemiology of R-plasmids were also studied.

The majority of S. typhimurium strains (90.5%) were untypable by phage typing. Only 18 strains (9.5%) were phage typable. The phage untypable strains isolated from northern (57) central (65), and southern (50) regions of India could be subgrouped into 24, 12 and 16 different plasmid profiles respectively. Heterogeneity was the prominent feature although most of the plasmid profiles were related among strains isolated from particular place. A great diversity among small plasmids (2.7–8.3 kb) made subgrouping of majority strains (71%) with R-pattern ApCmKmSmSuTcTp possible. Conjugation studies and plasmid profile analysis of transconjugants revealed all the strains to harbour non conjugative non-auto transmissible plasmids with the exception of 7.2 and 2.7 kb plasmids which were not mobilizable.  相似文献   


6.
Twenty-four isolates representing 6 species of Campylobacter were screened for plasmids. A large plasmid with an approximate molecular weight of 38 Mdal was detected in 5 C jejuni isolates originally recovered from diarrheic human beings, in one isolate of C coli recovered from diarrheic pigs, and in 1 isolate of C sputorum ssp mucosalis and 2 isolates of C hyointestinalis recovered from pigs with proliferative enteritis. One isolate of C coli and 1 isolate of C hyointestinalis contained an additional smaller plasmid with an approximate molecular weight of 1.6 Mdal; this plasmid was partially mapped by restriction endonuclease digestion. Fifteen Campylobacter isolates contained no detectable plasmids: 2 C coli, 2 C sputorum ssp mucosalis, 2 C fecalis, 1 C fetus ssp fetus, and 8 C hyointestinalis isolates. In summary, 37.5% of the Campylobacter isolates contained a 38-Mdal plasmid, with 8% having both 38 Mdal and 1.6-Mdal plasmids; 62.5% contained no detectable plasmids.  相似文献   

7.
Actinobacillus (Haemophilus) pleuropneumoniae plasmids were characterized and classified. They were isolated from A pleuropneumoniae strains different in serotype, year isolated, or location from which isolated. Six of 8 plasmids encoded streptomycin (Sm) and sulfonamide (Su) resistance (SmSu). One of the other plasmids, pVM105, encoded ampicillin (Ap) resistance and another, pHM0, encoded no drug resistance. All SmSu plasmids were transferred to Escherichia coli strains by transformation. Among them, pABO and pMS260 were 8.1 kb and incompatible with each other; they were stable in E coli. The other SmSu plasmids, pHM1, pVM104, pVM106, and pKD25, were 4.3 kb and did not replicate stably in E coli. The former SmSu plasmids were mobilized in E coli strains by a plasmid RP4, which belonged to incompatibility (Inc) group P, but the latter plasmids were not. Further, each 8.1-kb SmSu plasmid and each 4.3-kb plasmid had the same respective restriction pattern. These results indicated that there were at least 2 types of SmSu plasmids in A pleuropneumoniae. The 2 types were classified in 2 groups: H1(pMS260 and pABO) and H2(pHM1, pVM104, pVM106, and pKD25). The H1 and H2 plasmids belonged to different Inc groups, and H2 plasmids belonged to a different Inc group from that of pHMO and pVM105.  相似文献   

8.
Twenty-four strains of Salmonella enteritidis, isolated from several outbreaks of salmonellosis from different poultry farms in India, were checked for the plasmid profile and detection of virulence gene(s) by PCR. Most of the strains contained only a single plasmid of 55 kb. Additional plasmids of 23.2 kb and 8.7 kb were seen in one of the strains, and another strain carried only two plasmids of 23.2 kb and 8.7 kb. Four strains did not carry any plasmid. PCR amplification showed the presence of virulence-associated genes in all the isolates harbouring the 55 kb plasmid. Intraperitoneal inoculation of mice, with most of the strains carrying the 55 kb plasmid, caused 100% mortality. Most strains lacking the 55 kb plasmid were avirulent. In chickens, oral inoculation of the S. enteritidis strains carrying the 55 kb plasmid produced 40–100% mortality, with characteristic signs of salmonellosis. Oral inoculation of strains lacking the 55 kb plasmid did not cause any mortality. Hence, it appears that the large plasmid of S. enteritidis probably contributes towards virulence in mice and chickens.  相似文献   

9.
本试验旨在对临床分离的猪源大肠埃希氏菌耐药基因进行初步定位。采用常规细菌分离培养、16S rRNA PCR扩增和序列测定方法从江西省3个规模化猪场送检的子宫脓液中分离鉴定病原菌,并通过质粒提取、转化大肠埃希氏菌DH5α感受态细胞及药敏试验对临床分离株的耐药基因进行初步定位。结果显示,分离鉴定到3株大肠埃希氏菌,其中JX-22分离株仅对氧氟沙星、大观霉素敏感,JX-26分离株仅对链霉素、氧氟沙星等4种药物敏感,JX-28分离株仅对氧氟沙星等3种药物敏感,均为多重耐药菌;3株大肠埃希氏菌均可纯化到分子质量大小不一的质粒。分离株、质粒转化菌及大肠埃希氏菌DH5α感受态细胞药敏试验对比结果显示,3株大肠埃希氏菌的耐链霉素、林可霉素、甲硝唑、氨苄西林、阿莫西林、大观霉素、丁胺卡那基因,JX-22和JX-26分离株的耐多西环素、氟苯尼考和复方新诺明基因,JX-22分离株的耐头孢曲松基因,JX-28分离株的耐头孢曲松、头孢噻肟、诺氟沙星基因均定位于细菌质粒上;JX-28分离株的耐多西环素、氟苯尼考和复方新诺明基因,JX-22分离株的耐诺氟沙星基因和JX-26分离株的耐头孢曲松、头孢噻肟基因均定位于其染色体上;3株分离株均无氧氟沙星耐药基因。本试验初步确定3株多重耐药猪源大肠埃希氏菌的大部分耐药基因定位于质粒上,为进一步研究猪源大肠埃希氏菌的耐药机理和有效控制措施奠定基础。  相似文献   

10.
The aim of this study was to determine the molecular epidemiology of cefoxitin-resistance Escherichia coli identified in cattle entering feedlots and determine if there were any similarities to E. coli causing human infections in Canadian hospitals. A total of 51 E. coli were isolated from a total of 2483 cattle entering four feedlots in southern Alberta, Canada. DNA fingerprinting using pulsed-field gel electrophoresis revealed thirty-two unique patterns with two major clusters observed comprised of Cluster A (11 strains) and Cluster B (7 strains). PCR and sequence analysis revealed 38 isolates (74.5%) harboured bla(CMY-2), whereas the remainder were found to contain mutations in the promoter region of the chromosomal ampC gene, which has been previously associated with cefoxitin resistance. No resistance to nalidixic acid, ciprofloxacin, or amikacin was observed in the clinical isolates. bla(CMY-2) harbouring plasmids were transferred to E. coli DH10B. All of the plasmids carrying bla(CMY-2) contained the A/C replicon and also harboured other resistance genes. Plasmid fingerprinting using BglII revealed 17 unique patterns with all but one clustering within 70% similarity. Comparison of the plasmid fingerprints to those isolated from human clinically significant E. coli in Canada during a similar time period [Mulvey, M.R., Bryce, E., Boyd, D.A., Ofner-Agostini, M., Land, A.M., Simor, A.E, Paton, S., 2005. The Canadian Hospital Epidemiology Committee, and The Canadian Nosocomial Infection Surveillance Program, Health Canada. Molecular characterization of cefoxitin resistant Escherichia coli from Canadian hospitals. Antimicrob. Agents Chemother. 49, 358-365] revealed four strains that harboured bla(CMY-2) A/C replicon type plasmid with fingerprint similarities of greater than 90% to the ones identified in E. coli from the cattle in this study. These findings highlight the potential linkage of multidrug resistant organisms in food producing animals and human infections in Canadian hospitals. The plasmids conferred resistance to multiple antibiotics which could limit options for the treatment of infections caused by these strains.  相似文献   

11.
The aetiology of neonatal porcine diarrhoea was studied in 15 different herds located in the north-western region of Venezuela. Of 56 strains of Escherichia coli analyzed, 16 (28.6%) were shown to produce heat-stable (STa) enterotoxin, as detected by infant mouse assay. Only four of these STa+ isolates also possessed the K88 pilus antigen, two were 987P+ and none possessed the K99 antigen, leaving 10 STa+ samples in which no pilus antigen was identified. Among the 40 STa negative samples were six K88+ specimens, one K99+, four 987P+, one which reacted as K88+ + K99+ and one K88+ + 987P+. Considering as pathogenic any strain showing at least one of the characters studied, pathogenic E. coli were detected with an overall frequency of 42.9%, being more prevalent during the second week of life. An electrophoretic analysis of the plasmid content of the field isolates of E. coli, revealed the presence of numerous species of extrachromosomal DNA, although no direction association could be made between a particular plasmid and any of the pathogenic characteristics identified. Results of Southern blot analysis indicate that the STa enterotoxin was preferentially encoded within an endemic plasmid of 4.9 Md. Other plasmids present in the E. coli isolates could be related to antibiotic resistance. With the exception of one strain, all E. coli isolates were resistant to more than one of the nine drugs tested; multiresistant E. coli were frequently isolated, including four strains which were resistant to seven antibiotics.  相似文献   

12.
猪源大肠杆菌耐药性质粒的监测研究   总被引：1，自引：1，他引：0  
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   

13.
Virulence factors of avian Escherichia coli   总被引：9，自引：0，他引：9  
A total of 45 strains of Escherichia coli isolates from chickens with colisepticemia were examined for virulence factors commonly found in pathogenic groups of E. coli. These strains were studied for the following: pathogenicity in 1-day-old chicks; toxin, hemolysin, and colicin production; cell invasiveness and adherence; hemagglutination for fimbriae detection; serum resistance; aerobactin production in iron-limited conditions; and plasmid content. The characteristics exhibited by virulent strains were invasion for HeLa and chicken fibroblast cells, serum resistance, colicin V, and aerobactin production. None of the isolates were toxigenic or positive in hemagglutination tests. The molecular genetic studies of the virulence factors by agarose electrophoresis showed that the plasmids of these strains are of high molecular weight.  相似文献   

14.
Streptococcus suis isolates recovered from diseased animals in Quebec and western Canada and from human cases in Europe were tested for their susceptibility to different antimicrobial agents and screened for their plasmid content. Most isolates from Quebec were clindamycin, erythromycin, and tetracycline resistant; animal isolates from western Canada were notably less resistant to clindamycin and erythromycin, whereas human isolates were considerably more susceptible to most antimicrobials tested. More than 60% of isolates had plasmids that ranged from 1.5 to 35 kilobases (kb). Of the 7 plasmid profiles found, 2 were particularly frequent in isolates from Quebec and western Canada, suggesting the presence of epidemic strains in the swine population. A particular plasmid band of about 5 kb was present in most Canadian isolates. When this band was used as a probe in colony and Southern blot hybridization, most isolates harboring the 5-kb plasmid hybridized, even though their plasmid profiles were different. Human isolates from Europe differed in their plasmid content from Canadian isolates of animal origin. Although a high degree of antimicrobial resistance was associated with the presence of plasmids in most isolates, it was not possible to establish a causative relationship.  相似文献   

15.
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   

16.
A total of 22 Salmonella enterica serotype Enteritidis (S. Enteritidis) strains isolated from human and chicken were subjected to DNA fingerprinting by repetitive sequence PCR using ERIC and BOX primers, antibiotic resistance and plasmid patterns. Both ERIC and BOX PCR amplification data revealed a highly genetic homogeneity between isolates from human and chicken except one isolate, which originated from chicken and showed a different DNA band pattern from others. Eleven of 22 S. Enteritidis isolates (50%) were resistant to more than one antibiotics and characterized by 5 resistance patterns. The most common pattern was penicillin resistant (63.6%). Only one isolate from chicken showed a multiple drug resistance patterns to 4 antibiotics. All 22 S. Enteritidis isolates harbored more than two plasmids with eight different plasmid profiles including two to six plasmids with approximate molecular size ranging from 1.9 to 21 kb. A band of 15 kb size was detected in all isolates tested, however, the band sizes smaller than 15 kb were found only in isolates from chicken.  相似文献   

17.
The extent of genotypic and phenotypic diversity of Edwardsiella tarda isolated from pond sediment was assessed by SDS-PAGE, Plasmid Profiling and ERIC-PCR. SDS-PAGE of whole cell protein extracts reveals 20-23 discrete bands with molecular wt of 14-110 kDa. Several bands with molecular weight range of 38-83 kDa were present in all the isolates. Numerical analysis of protein electrophoregram delineated the isolates into four clusters. Two different types of plasmids having molecular mass of 23 kDa and 29 kDa were obtained by plasmid profiling. About 51% of the isolates carried both the plasmids. ERIC-PCR generates 3-7 bands with molecular mass of 14-1013 bp. Numerical analysis differentiated the ERIC pattern into 5 clusters at 60% similarly level. It was concluded that out of three methods ERIC-PCR was found to be more sensitive for intraspecific typing of E. tarda and can be used as a potential tool for epidemiological studies in the future.  相似文献   

18.
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   

19.
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   

20.
Restriction endonuclease digestions were performed on plasmids purified from Moraxella bovis isolates GRS, Newport, and IBH64. It was determined from single and double digestions of plasmid DNA that GRS and Newport isolates carried 3 large plasmids having molecular sizes of 43.8, 41.3, and 32.8 kilobases (kb). Digestion of the 3 large plasmids and restriction endonucleases Hae III, HindIII, Nde I, and Ava I strongly indicated that these isolates shared structurally identical large plasmids. Timed single digestions with Ava I revealed that the IBH64 isolate carried 2 large plasmids having molecular sizes of 45 and 32.8 kb. The 32.8-kb plasmid was the only large plasmid that appeared to be shared by all 3 M bovis isolates. Two isolates, Newport and IBH64, carried small plasmids in addition to the large plasmids. Restriction maps were constructed for the 43.8-, 41.3-, and 32.8-kb plasmids.  相似文献   

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