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 15 毫秒
1.
Pasteurella multocida B:2 is responsible for haemorrhagic septicaemia in cattle and buffaloes, causing severe economic losses in the developing countries. In the present study, the ahpA gene of P. multocida B:2 (P52) was cloned, sequenced and compared with the previously reported ahpA gene sequence in P. multocida A:1, which is responsible for its haemolytic phenotype. E. coli DH5a cells were further transformed with recombinant plasmid carrying the ahpA gene from P. multocida B:2 (P52) but SDS-PAGE analysis failed to show the expression of haemolysin protein. Slight haemolysis was albeit observed in horse blood agar plates streaked with recombinant E. coli carrying the ahpA gene. Our study indicates that there is 99.6% similarity and 0.4% divergence between ahpA gene of P. multocida B:2 (P52) and P. multocida A: 1, while membrane topology analysis has predicted that ahpA is an inner membrane protein with two strong hydrophobic regions at the N and C terminals. The presence of significant homology in ahpA sequence in A: 1 and B:2 perhaps suggests a common mechanism of pathogenesis in different species of animals.  相似文献   

2.
The fragility of erythrocytes is easily demonstrated by their ability to withstand osmotic swelling and lysis in solutions of increasingly hypotonic saline. In healthy animals a plot of percentage haemolysis against increasing hypotonicity produces a sigmoid curve. Using the same data a derivative curve calculated from haemolytic increments shows a normal distribution of fragility within samples. In enhanced fragility due to immune-mediated haemolytic anaemia, these profiles of haemolysis are markedly altered and the derivative curve becomes multiphasic, indicating the presence of subpopulations of erythrocytes with differing fragility ranges. Analysis of these profiles in a case of intravascular immune-mediated haemolysis in a horse provided useful graphic information for diagnosis and prognosis. In particular, the size of the subpopulation showing increased fragility could be assessed in the acute phase and monitored during recovery.  相似文献   

3.
The usage of antimicrobials for treatment of mink and the occurrence of antimicrobial resistance among the most important bacterial pathogens in mink was investigated. The aim of the study was to provide data, which may serve as a basis for the formulation of recommendations for prudent use of antimicrobials for mink. A total of 164 haemolytic staphylococci, 49 haemolytic streptococci, 39 Pseudomonas aeruginosa, 13 Pasteurella multocida, and 1093 Escherichia coli isolates from Danish mink were included in the study. A high frequency of resistance among S. intermedius was found for tetracyclines (54.7%), followed by penicillin (21.7%), lincosamides (20.4%), macrolides (19.1%), and spectinomycin (18.5%). Very low frequencies of resistance were recorded for other antimicrobials. The highest frequency among the E. coli isolates was recorded for ampicillin, streptomycin, sulphonamides, and tetracyclines, whereas resistance to other antimicrobials was rare. All P. aeruginosa were sensitive to gentamicin and colistin and sensitive or intermediate to enrofloxacin, whereas most isolates were resistant to all other antimicrobials. All P. multocida and haemolytic streptococci were sensitive to penicillin. There was a steady increase in the use of antimicrobials during the period 2001-2006, the majority of the prescribed amount being extended spectrum penicillins followed by aminoglycosides, sulphonamides with trimethoprim, and macrolides.  相似文献   

4.
Haemolysin is one type of virulence factor that assists in the pathogenesis of Escherichia coli. Currently, hemolytic activity in E. coli has been attributed to haemolysin genes found in either uropathogenic or enterohemorrhagic E. coli. Both haemolysins are classified as RTX toxins because they both have repeats in toxin domains and share similar operon organization, sequence homology, and mechanisms of action. Haemolytic avian E. coli isolates, however, lack either E. coli haemolysin gene. To investigate the avian E. coli haemolysin, a genomic library was made from an avian pathogenic E. coli. A haemolytic clone that was isolated was shown to contain homology with sheA, an E. coli K- 12 gene which causes haemolysis when present in high copy number. The cloned haemolysin gene, hlyE, lacked the conserved amino acid sequence and accessory genes common to all RTX toxins. DNA hybridizations and polymerase chain reaction amplifications showed that the nucleotide sequences homologous to hlyE were not present in a collection of three O157: H7 E. coli, five haemolytic canine uropathogenic E. coli, one haemolytic O26 E. coli, and three haemolytic avian pathogenic E. coli. Thus we have identified a new E. coli haemolysin distinct from the RTX haemolysins and have shown that some avian pathogenic E. coli possess a haemolysin with no apparent homology to hlyE or RTX haemolysins.  相似文献   

5.
The objective of this study was to investigate the haemolytic and cytotoxic activity of Pasteurella multocida B:2 strains, originally from cases of haemorrhagic septicaemia in cattle. All six P. multocida B:2 strains were non-haemolytic on sheep blood agar (SBA) and horse blood agar (HBA) when grown aerobically and on SBA anaerobically but they were haemolytic on HBA when grown anaerobically. No haemolytic activity against horse red blood cells was detected in culture supernates from aerobically or anaerobically grown cultures and only very weak haemolytic activity was obtained in supernates or pellet fractions from sonicated cells. However, after repeated extraction of sonicated cells with Tween 80, haemolytic activity was found in various cell fractions, both Tween-soluble and -insoluble. The Tween-extracted putative haemolysin and other bacterial fractions were also cytotoxic for mouse macrophage-like J774.2 cells. Further characterisation of the putative haemolysin revealed it to be a heat-labile, non-pore-forming protein of molecular weight >10 kDa whose activity was completely destroyed by trypsin and greatly reduced with protease and proteinase K treatment. Congo red also reduced the haemolytic activity. Non-denaturing gel-electrophoresis and RBC agar overlay revealed clear haemolytic zones but suggested that Tween was bound to some component of the P. multocida B:2 fractions and was responsible, to some extent, for the haemolytic activity observed. However, the effect of heat and other reagents on the Tween-extracted fractions and the lack of haemolytic activity in different Tween-extracted cell fractions of organisms other than P. multocida suggested that some proteinaceous component of the organism could indeed act as a haemolysin. This putative haemolysin may be one of the virulence attributes of P. multocida, but its characterisation and role in pathogenesis require further study.  相似文献   

6.
Four cases of experimental copper poisoning in sheep were examined. Light microscopical and ultrastructural alterations of erythrocytes were observed a few hours before a significant haemolysis was evident. Heinz body formation in otherwise unchanged red cells was the first morphological alteration observed. The Heinz bodies were predominantly membrane-attached. During the haemolytic crisis severe erythrocytic distortion, structural membrane alteration and Heinz body-containing ghost cells were observed. Erythrophagocytosis was mainly located to the RE cells of the spleen. Intrafollicular necroses were found in all histological sections from the spleen. Pathological changes in liver and kidney were comparable to those of earlier reports, comprising hepatocellular and renal tubular necrosis.  相似文献   

7.
Haemolytic activities of Trichophyton (T.) mentagrophytes were detected and characterized by qualitative and quantitative assays. On Columbia agar supplemented with blood from horses, cattle or sheep, T. mentagrophytes expressed a strong zone of complete haemolysis. No haemolytic activities could be detected in the closely related T. verrucosum var. ochraceum. The same results were obtained after cultivation of the fungi on sterile cellulose acetate filters placed on the surface on Columbia blood agar. After removal of the filter, complete haemolysis was detected below the colony of T. mentagrophytes. A soluble haemolysin from culture supernatant of this strain was isolated and partially purified. Specific haemolytic activity per mg protein was enriched 2.6-fold in filtrate F(1), a fraction obtained as filtrate after filtration through 3kDa cut-off membranes. The partially purified haemolysin was neither affected by proteinase K treatment, nor by high and low temperatures, suggesting that it represents a small peptide haemolysin. Accordingly, in a commercial enzymatic activity test only the crude culture filtrate, but none of the subsequent purification fractions showed reactivity. Evaluation of the specificity of the haemolysin using erythrocytes from different mammalian species revealed that sensitivity was highest to those of equines, followed by erythrocytes from sheep, cattle, swine, dogs and humans. None of the erythrocytes was lysed by filtrate F(1) from T. verrucosum var. ochraceum. Furthermore, different eukaryotic cell lines from different species were tested in their sensitivity to cytolytic activities of the haemolysin, but no membrane damage could be detected.  相似文献   

8.
The sera from 12 out of 29 half-sibs of the New Zealand White breed of rabbit were inactive, when used as complement, in blood-typing tests of bovine erythrocytes. This defect was found to be due to a deficiency in the activity of the component C6. A dilution of 1:380 of pooled normal rabbit sera and a dilution of 1:520 of pooled normal bovine sera were capable of restoring, to 63%, the haemolytic capacity of the defective rabbit sera. The rate of haemolysis varied from 4% to 100% when the defective sera were restored by sera from different sets of monozygous bovine twins.  相似文献   

9.
Some of the parameters of the radial haemolysis test were studied, and the test was used to determine antibody titres of sera obtained from patients involved in the epidemic outbreak of influenza-A/Port Chalmers, 1975. The sensitivity of the method was found to depend on the degree of erythrocyte sensitisation. An enlargement by 40 per cent of the haemolytic halo diameter should be considered and treated as antibody rise, if the reaction was to used in serological diagnosis under the conditions tested. The findings were in agreement with the complement fixation reaction in 48 per cent of all cases and with the haemagglutination inhibition test in 53.8 per cent.  相似文献   

10.
为建立一种快速准确检测兔多杀性巴氏杆菌(P.multocida)的PCR方法,本研究以P.multocida的高度保守的16S rRNA为靶基因,参考已公布的P.multocida的16S rRNA基因设计1对特异性引物,优化PCR反应条件,建立了P.multocida PCR快速检测方法。该PCR方法的敏感性达到60 cfu/mL,采用该PCR方法扩增P.multocida标准株和分离株均能扩增出643 bp的目的片段,扩增兔大肠杆菌、支气管败血波氏杆菌结果为阴性,证明本实验所建立的P.multocida PCR检测方法快速、敏感、特异、可靠,可用于P.multocida的快速鉴定与诊断。同时用建立的PCR方法对临床疑似病兔的脏器分离菌进行扩增,可扩增出目的条带,与细菌的分离结果相一致。  相似文献   

11.
Pasteurella multocida group B, serotype 3, was isolated from sinusitis-affected khaki Campbell ducks. To study the role of P. multocida in sinusitis, commercial khaki Campbell ducks were experimentally infected with P. multocida alone or combined with Escherichia coli. In Expt. 1, experimental ducks were infected with P. multocida intranasally or ocularly. A comparison was done by intranasal inoculation with pooled nasal discharge from the affected ducks or phosphate-buffered saline. The ducks intranasally inoculated with the nasal discharge or P. multocida showed sinusitis. In Expt. 2, E. coli alone or a combination of P. multocida and E. coli was intranasally inoculated into experimental ducks. The ducks intranasally inoculated with the combination of P. multocida and E. coli had sinusitis, the same as found in the field but less severe than that of the field cases. Pasteurella multocida was already present in litter/floor of duck farms. We concluded that P. multocida played a role in induction of sinusitis. However, the sinusitis in ducks may be initiated by poor management, especially in the brooding period of ducks.  相似文献   

12.
A substance, concluded to be Corynebacterium ovis exotoxin on the basis of properties shared, was found to have haemolytic activity below pH 6 and red cell adhesion activity at neutral or slightly alkaline pH. An acidified, solid blood agar medium was used to demonstrate the extent of haemolysis that could be obtained at optimal pH and its inhibition by immune serum. Culture in a liquid medium giving rise to a suitably acidic pH allowed titration for haemolytic activity by the exotoxin and use of supernatant in a haemolysis-inhibition test to detect antitoxin.  相似文献   

13.
79 strains of P. multocida were investigated, mostly isolated from porcine nasal cavities, and a mannose-resistant hemagglutination with guinea pig and human group 0, but not with porcine erythrocytes was found. Fimbriae as adhesins were demonstrated only on 2 strains. A correlation between capsular type, hemagglutination, fimbriation and toxigenicity on the examined P. multocida strains was not observed. Three strains were investigated for the adherence to the nasal mucosa of neonatal pigs; aggregates shown by scanning electron microscopy indicate colonization; a correlation of adherence with surface proteins and slime production of P. multocida is discussed.  相似文献   

14.
Searching for potential virulence markers of Ureaplasma (U.) urealyticum and Mycoplasma (M.) hominis, simple laboratory methods were used to detect strain specific properties. Haemadsorption, sperm adsorption, haemolysis, and peroxide formation were tested on clinical isolates and type strains of U. urealyticum and M. hominis in comparison to reference strains of seven other Mycoplasma species. In contrast to M. bovis, M. gallisepticum and M. pulmonis, all strains of M. hominis and U. urealyticum failed to adsorb human spermatozoa and erythrocytes from five vertebrate species to their colonies. Unexpectedly, colonies of M. arthritidis PG 6 adsorbed both human erythrocytes and spermatozoa. Using various methods, the known haemolytic and peroxide activities of the reference strains could be confirmed. None of the U. urealyticum strains tested demonstrated lysis of human or ovine erythrocytes or peroxide production. On the other hand, 76 of 108 isolates of M. hominis showed an alpha'- or beta-haemolysis of different degree. However, this phenomenon could not be reproduced in all cases and it was not attributable to the activity of a peroxide. None of the methods used in this study were found to be suitable for detection of possible virulence factors of U. urealyticum or M. hominis.  相似文献   

15.
The course of haemolytic anaemia, caused by immune antibody, was characterised in greater detail with reference to eight heads of young cattle examined for plasma haemoglobin, bilirubin, inorganic phosphorus, and calcium in serum. Inorganic serum phosphorous values were found to decline strongly immediately after the onset of iso-immune serum transmission. Severe haemolysis developed, but only moderate haemoglobinaemia and no haemoglobinuria at all occurred. Bilirubin was increased over a long time, which seemed to support the assumption of gradual erythrocyte decomposition. The usefulness of inorganic serum phosphorus determination as an approach in support of early diagnosis of aggravating haemolysis is confirmed and recommended for metabolic monitoring of cattle herds.  相似文献   

16.
The resistance to anti-microbial agents of bacteria isolated from pathological conditions of birds in Victoria, 1978 to 1983, was determined for isolates of Escherichia coli, Salmonella species, Staphylococcus aureus, Pasteurella multocida, P. anatipestifer, Yersinia pseudotuberculosis and Haemophilus paragallinarum. The isolates of E. coli had a high prevalence of resistance to tetracycline and sulphonamides, and a lower prevalence of resistance to furazolidone and sulphamethoxazole-trimethoprim. The isolates of Salmonella spp commonly had resistance to tetracycline, sulphonamides, furazolidone and sulphamethoxazole-trimethoprim. Almost half the isolates of S. aureus showed resistance to lincomysin and many showed resistance to penicillin. Resistance to tetracycline was found in isolates of P. multocida, P. anatepestifer and Y. pseudotuberculosis. Some isolates of H. paragallinarum showed resistance to sulphonamides, streptomycin and sulphamethoxazole-trimethoprim.  相似文献   

17.
The clinical, haematological and immunological findings in 24 dogs with Coombs' positive haemolytic anaemia are described; 33% were Old English Sheepdogs. Dogs with intravascular haemolysis had a shorter history of illnesses, more severe clinical signs including vomiting, jaundice and fever, and had a poor survival rate compared to dogs with extravascular haemolysis. The anaemia was severe and regenerative in 18 dogs, and was characterised by spherocytosis and microscopic red cell agglutination, with leukocytosis. Serum IgG levels were elevated in 20 dogs, and changes in IgM, IgA, C3 and C4 were found. Antinuclear antibody was also demonstrated in 13 dogs, of which 7 were Old English Sheepdogs. It is suggested that a distinct multisystem autoimmune syndrome exists within the local Old English Sheepdog population.  相似文献   

18.
A Somali cat was presented with recurrent anorexia, lethargy, vomiting and icterus. A macrocytic-hypochromic, regenerative haemolytic anaemia was identified and hereditary pyruvate kinase deficiency was confirmed by means of breed-specific DNA mutation analysis. The case was complicated by the presence of markedly elevated serum liver enzyme activities, hyperbilirubinaemia, coagulopathy and ultrasonographic evidence of gall bladder choleliths and extrahepatic bile duct obstruction. The choleliths consisted of 100 per cent bilirubin, likely because of chronic haemolysis and haeme degradation. In conclusion, haemosiderosis and bilirubin cholelithiasis can be a consequence of chronic haemolysis in pyruvate kinase-deficient cats, as seen in human beings with a variety of chronic haemolytic disorders.  相似文献   

19.
Besides the well-known O157:H7 clone causing enterohaemorrhagic colitis and haemolytic uraemic syndrome in Europe, Japan and North America, the number of Escherichia coli isolates with non-motile (NM) phenotype has considerably increased. We supposed that spontaneous antibiotic resistance mutation could cause this phenotypic change. To model our hypothesis we isolated rifampicin--(Rif) and ampicillin--(Amp) resistant mutants from E. coli O157:H7 prototype strains 7785 and EDL933. Among Rifr mutants we could isolate strains with no or reduced motility, while the Ampr mutants became hypermotile. The biochemical profile of the mutants had not changed but phage sensitivity and generation time of the mutants were altered. Among the representative strains we did not find polymorphism with Southern blot analysis and no polymorphism was found in the fliC gene of the mutants. The described characteristics have proven to be stable. In a mice virulence assay by intravenous infections the virulence of the derivatives was also found to be changed. In summary, we found that the antibiotic-resistant phenotype in E. coli O157:H7 was coexpressed with several other phenotypic changes including motility and virulence. It can be assumed that expression of the involved phenotypes may be under the influence of a common regulatory cascade. Further work is needed to identify the components and mechanism of this regulatory system.  相似文献   

20.
Sheep complement (C) is haemolytic for sheep erythrocytes sensitized with rabbit antibody (sheep E-rabbit A) provided serum is used as soon as possible after collection. If left at 4 °C to separate from the clot, serum C activity for sheep E-rabbit A is markedly reduced. Heparinized plasma retains its haemolytic titre for at least 24 h at 4 °C. Plasma from Mg2+-ethyleneglycoltetraacetic acid (EGTA) blood is non-haemolytic, but addition of Ca2+ partially restores the titre. A high concentration of rabbit A is necessary to sensitize sheep E.Sheep C is haemolytic for human erythrocytes sensitized with sheep antibody (human E-sheep A) in the presence of Mg2+-EGTA. This C activity is stable at 4 °C for 24 h in serum, Mg2+-EGTA plasma and heparinized plasma. Haemolytic activity of serum heated at 50 °C for 30 min was restored by a factor B containing CM-cellulose fraction of foetal lamb serum in the presence of Mg2+-EGTA for human E-sheep A but not sheep E-rabbit A.These findings show that sheep C haemolysis of sheep E-rabbit A requires a Ca2+-Mg2+-dependent pathway that is labile in vitro for 24 h at 4 °C.  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