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1.
Several modern electron microscopy techniques were used to examine Pasteurella haemolytica (biotype A, serotype 1) (strain B122) recovered from experimentally infected cattle and in situ within the lung tissue of experimentally infected cattle. Glycocalyx four to five times thicker than that seen on P. haemolytica grown in vitro was evident on bacterial cells recovered from live infected calves by pulmonary lavage. Fimbriae were also present on cells recovered by lavage. A thick glycocalyx was also seen on P. haemolytica-A1 within the lungs of experimentally infected cattle at necropsy. In summary, cells of P. haemolytica-A1 in experimentally infected cattle have fimbriae and glycocalyx on their cell surfaces and these structures appear to be important in bacterial colonization of the bovine respiratory tract and pathogenesis of shipping fever (Pasteurella) pneumonia.  相似文献   

2.
Several electron microscopic techniques were used to examine the surface of cells of Pasteurella haemolytica (biotype A, serotype 1) grown in vitro. All methods showed the presence of a very extensive glycocalyx on logarithmic phase (6 h) cells grown in liquid media. The anionic glycocalyx of these cells stained well with ruthenium red, but collapsed during dehydration for electron microscopy unless stabilized with specific antibodies. When the same techniques were used to examine cells in the stationary phase (18 h) the glycocalyx was much reduced. Large numbers of fimbriae were seen on both 6 h and 18 h cells grown in fluid media without shaking. In summary, logarithmic phase cells of P. haemolytica have both fimbriae and extensive anionic glycocalyx at their surface and we suggest that either or both of these structures may be important in the colonization of the bovine respiratory tract and the subsequent pathogenesis of Pasteurella pneumonia.  相似文献   

3.
On the basis of recent observations that immunoglobulin (Ig) E antibodies specific for bacterial antigens occur in the serum of persons with chronic respiratory tract disease, we used bovine epsilon chain-specific antiserum to investigate the possibility that IgE antibodies are induced in cattle infected with Pasteurella. Using enzyme-linked immunosorbent assay and Western blotting techniques, we studied bovine sera to detect and quantitate the presence of IgE antibodies specific for antigens of Pasteurella. Immunoglobulin E antibodies reactive with whole formalinized P haemolytica, potassium thicyanate, and saline solution extracts were detected in serum of calves with bronchopneumonia, feedlot steers with interstitial pneumonia, as well as nonaffected penmates, and adult dairy cows. The role of parenteral vaccination in eliciting an IgE response was examined in healthy calves; vaccination with a Pasteurella bacterin failed to induce an IgE response. Adsorption studies were done to demonstrate the specificity of the antibodies for Pasteurella. Enzyme-linked immunosorbent assay absorbance values were significantly decreased by adsorption with P haemolytica, whereas adsorption with other gram-negative bacteria only moderately decreased serum absorbance values. To begin identification of the antigen(s) to which the IgE binds, Western blotting of P haemolytica extract with sera from calves with bronchopneumonia was done. A dense band of protein (approximately 60,000 daltons) reacted strongly with IgE in the highest titer sera. These results indicate that Pasteurella-specific IgE antibodies are not readily induced by parenteral vaccination, but can be found in serum of some cattle, possibly induced by existing or previous infection.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

4.
Mannheimia haemolytica and bovine respiratory disease   总被引：1，自引：0，他引：1  
Mannheimia haemolytica is the principal bacterium isolated from respiratory disease in feedlot cattle and is a significant component of enzootic pneumonia in all neonatal calves. A commensal of the nasopharynx, M. haemolytica is an opportunist, gaining access to the lungs when host defenses are compromised by stress or infection with respiratory viruses or mycoplasma. Although several serotypes act as commensals, A1 and A6 are the most frequent isolates from pneumonic lungs. Potential virulence factors include adhesin, capsular polysaccharide, fimbriae, iron-regulated outer membrane proteins, leukotoxin (Lkt), lipopolysaccharide (LPS), lipoproteins, neuraminidase, sialoglycoprotease and transferrin-binding proteins. Of these, Lkt is pivotal in induction of pneumonia. Lkt-mediated infiltration and destruction of neutrophils and other leukocytes impairs bacterial clearance and contributes to development of fibrinous pneumonia. LPS may act synergistically with Lkt, enhancing its effects and contributing endotoxic activity. Antibiotics are employed extensively in the feedlot industry, both prophylactically and therapeutically, but their efficacy varies because of inconsistencies in diagnosis and treatment regimes and development of antibiotic resistance. Vaccines have been used for many decades, even though traditional bacterins failed to demonstrate protection and their use often enhanced disease in vaccinated animals. Modern vaccines use culture supernatants containing Lkt and other soluble antigens, or bacterial extracts, alone or combined with bacterins. These vaccines have 50-70% efficacy in prevention of M. haemolytica pneumonia. Effective control of M. haemolytica pneumonia is likely to require a combination of more definitive diagnosis, efficacious vaccines, therapeutic intervention and improved management practices.  相似文献   

5.
Bovine lung explants were used in a study designed to compare the pathogenic effects of Pasteurella haemolytica type 1, a nonpathogenic organism Neisseria subflava, or the crude leukotoxin of P. haemolytica on alveolar macrophages and lung parenchymal cells. Concentrated, purified peripheral blood neutrophil suspensions were added with the bacteria to some explants. Duplicate pairs of cultures from each treatment group were fixed at regular intervals up to 24 hours after seeding and morphological changes were assessed by light and electron microscopy. Pasteurella haemolytica caused deterioration of alveolar macrophages within one hour but did not affect parenchymal cells for more than 12 hours. Neisseria subflava did not affect alveolar macrophages initially, but caused an accelerated deterioration after four hours. After 24 hours, bacterial overgrowth caused similar deterioration of all cells in explants seeded with either bacterium. Alveolar macrophages phagocytosed large numbers of N. subflava but rarely ingested P. haemolytica. Added neutrophils did not have any discernible effect on any of the explants and did not potentiate bacterial effects. Addition of crude leukotoxin of P. haemolytica to the culture medium significantly accelerated alveolar macrophage deterioration without apparent effect on parenchymal cell survival. These results support the hypothesis that the severe tissue destruction of fulminant pneumonic pasteurellosis is not a direct result of bacterial infection.  相似文献   

6.
Antibody titers to Pasteurella haemolytica A1 in Ontario beef cattle.   总被引：12，自引：7，他引：5       下载免费PDF全文
Indirect bacterial agglutination titers to Pasteurella haemolytica A1 were determined in serum, thoracic, pericardial, or peritoneal fluid from cattle necropsied as part of the Bruce County Beef Project in 1979-80 and 1980-81. Antibody titers were also assayed in serum from 84 calves on entry to feedlots in the fall of 1979. Titers on entry were low compared to antibody levels at necropsy. Cattle which died with pneumonia, in particular those dying of fibrinous pneumonia (shipping fever), had lower levels of antibody to P. haemolytica than did those dying of other causes.  相似文献   

7.
Monoclonal antibodies (mAb) against both Pasteurella haemolytica A1 capsule and lipopolysaccharide (LPS) were produced. Anti-capsule mAb reacted with the homologous A1 serotype only, whereas mAb against LPS reacted with P. haemolytica serotypes A2, A5, A8, A12, A14 and A16 but not with 33 bacterial species or rough LPS mutant strains tested. Both capsule and LPS antigens were visualised on the surface of bacteria by immunogold electron microscopy. Neither of the mAbs demonstrated antibody-dependent complement-mediated killing in vitro but both facilitated phagocytosis in vitro.  相似文献   

8.
Immunity against pneumonic pasteurellosis was studied in calves after recovery from experimental respiratory disease with Pasteurella haemolytica. Nine calves were exposed to aerosols of parainfluenza-3 virus and Pasteurella haemolytica A1 six days apart to produce respiratory disease. After recovery from the disease, these nine principal and four control calves were challenged with aerosols of bovine herpesvirus 1 and P. haemolytica A1 four days apart. With this viral-bacterial challenge, the nine principal animals failed to develop clinical responses to this bacterial challenge and their lungs did not show the growth of P. haemolytica on cultures, whereas two of four control calves had elevated temperatures and developed necropurulent pneumonia with the isolation of P. haemolytica from the lungs. The principal calves had developed high levels of cytotoxin neutralizing antibodies in their sera following parainfluenza-3 virus-P. haemolytica infection. This demonstrated that immunity against pneumonic pasteurellosis can be achieved, with a suggestion that further search for an effective vaccine for P. haemolytica is warranted.  相似文献   

9.
The objective of this study was to design a multiplex PCR assay to identify Mannheimia haemolytica, Mannheimia glucosida and Mannheimia ruminalis. The multiplex PCR included primer sets HP, amplifying a DNA region from an unknown hypothetical protein, Lkt and Lkt2, amplifying different regions of the leukotoxinD gene, and 16S to amplify universal bacterial sequences of the 16S rRNA gene. Based on positive amplification, isolates were delineated as M. haemolytica (HP, Lkt, 16S), M. glucosida (HP, Lkt, Lkt2, 16S), or M. ruminalis (HP, 16S). The validity of the assay was examined against 22 reference strains within the family Pasteurellaceae and 17 field isolates (nasal) that had been collected previously from feedlot cattle and tentatively identified as M. haemolytica based on morphology and substrate utilization. Additionally, 200 feedlot cattle were screened for M. haemolytica using multiplex PCR. Forty-four isolates from 25 animals were identified as M. haemolytica. The PCR assay positively identified all M. haemolytica, as confirmed by phenotypic tests and clustering based upon cellular fatty acid methyl ester (FAME) profiles. Selected nasal isolates that exhibited evidence of haemolysis, but were M. haemolytica-negative based on PCR, were also confirmed negative by phenotypic and FAME analyses. The multiplex PCR assay required no additional phenotypic tests for confirmation of M. haemolytica, within the group of bacteria tested.  相似文献   

10.
Calves inoculated with Pasteurella haemolytica serovar 1 developed lesions of coagulation necrosis in the lungs that were sharply demarcated by leukocytes. The P haemolytica antigen was detected in the area of coagulation necrosis in histologic sections, using an immunoperoxidase technique. In the central area of the necrotic tissue, the bacterial antigen was diffusely presented in the necrotic alveolar wall, fibrin, serous exudate, and degenerated leukocyte. The bacterial antigen also was found in some groups of degenerating leukocytes around the necrotic tissue. The bacterial colonies among these leukocytes had strong specific reactions against P haemolytica. The bacterial antigen was observed in the cytoplasm of macrophages in alveoli around the necrotic lesion. These findings confirmed that coagulation necrosis is an important lesion in calves with pneumonia caused by P haemolytica.  相似文献   

11.
In vitro interactions of bovine pulmonary lavage cells (PLC) and pathogenic isolates of Pasteurella haemolytica biotype A, serotype 1, were examined, using a luminol-dependent chemiluminescence (LDCL) assay. The PLC containing high concentrations of bovine alveolar macrophages were incubated with living and heat-killed P haemolytica at bacteria to PLC ratio of approximately 1:1. Kinetics of the mean LDCL response of bovine PLC to heat-killed P haemolytica cells were characterized by a gradual increase in the amount of light emitted over 150 minutes followed by a slight decrease at 180 minutes. In contrast, the LDCL responses of reaction mixtures containing living P haemolytica were characterized by the development of a maximal response at 60 minutes followed by a continued precipitous decrease in light emission to background values by 150 minutes. Differences were not noticed in the LDCL response of PLC suspensions from the same cow to 3 P haemolytica isolates. In each instance, reaction mixtures containing heat-killed bacteria had a similar LDCL profile that was characterized by continuous production of light over 180 minutes, whereas all reaction mixtures containing living bacteria underwent a precipitous decrease in light emission, which eventually resulted in a complete cessation of chemiluminescence. The PLC suspensions from different cattle did not respond to bacterial stimuli uniformly, with respect to the amplitude or detailed nature of the LDCL profile. The time that lapsed between the addition of living P haemolytica to PLC suspensions and the complete cessation of chemiluminescence varied for different cows.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

12.
The purpose of this study was to determine the frequency of selected pathogens in the tissues of a group of feedlot cattle with chronic disease (most often respiratory disease and/or arthritis). Samples of lung and joint tissues from 49 feedlot animals that had failed to respond to antibiotic therapy were tested by immunohistochemical staining for the antigens of Mycoplasma bovis, Haemophilus somnus, Pasteurella (Mannheimia) hemolytica, and bovine viral diarrhea virus (BVDV). Mycoplasma bovis was demonstrated in over 80% of cases, including in 45% of joints and 71% of lungs tested. Mycoplasma bovis was the only bacterial pathogen identified in the joints. Haemophilus somnus and Pasteurella (Mannheimia) haemolytica were found in 14% and 23% of cases, respectively, and were confined to the lungs in all instances. Infection with BVDV was demonstrated in over 40% of cases. Mycoplasma bovis and BVDV were the most common pathogens persisting in the tissues of these animals that had failed to respond to antibiotic therapy.  相似文献   

13.
Five calves were inoculated intravenously with 10(8) colony forming units (cfu) of Pasteurella haemolytica A1; the mean score for pneumonic consolidation 3 days post-inoculation was 28%, and the mean clinical score was 7.8. Five calves inoculated intratracheally with 10(9) cfu of the same strain of P. haemolytica had comparable scores (34% and 8.8). Histological lesions of fibrinous pneumonia were similar in all calves. P. haemolytica was recovered from all but one of the affected lungs. From one calf killed in extremis 3 hours after intravenous inoculation, numbers of bacteria recovered from lung were 1,000-fold greater than from liver and spleen. A similar difference in bacterial numbers was also obtained from a gnotobiotic calf killed in extremis, 12 hours after intravenous inoculation of 10(8) cfu P. haemolytica. Evidence from these experiments supports the hypothesis that the blood-borne route is important in the pathogenesis of bovine pneumonic pasteurellosis.  相似文献   

14.
Five groups of range bred calves (four calves per group) were used to investigate the effect of stress on susceptibility to aerosol exposures with bovine herpesvirus-1 or Pasteurella haemolytica. Twelve calves were weaned, transported, processed at a commercial feedlot and transported to isolation facilities three days later. An aerosol challenge of either 10 colony forming units of P. haemolytica or 10 plaque forming units of bovine herpesvirus-1 virus was given to two groups of calves and the third group was not challenged. The fourth group was transported directly to the isolation facilities after weaning and aerosol challenged with P. haemolytica. The fifth group remained at the farm after weaning and was not challenged. All transported animals had elevated plasma cortisol levels which remained above normal for at least three days postchallenge. The blastogenic response of all calves was depressed after leaving the farm and remained depressed throughout the experiment. The suppression correlated well with elevated serum cortisol levels. Calves processed through the feedlot encountered bovine herpesvirus-1 because eight out of 12 animals seroconverted to this antigen. Most calves seroconverted to P. haemolytica whether they were experimentally challenged or not. Where the unchallenged calves encountered P. haemolytica is unknown. Calves challenged with bovine herpesvirus-1 but not with P. haemolytica, had significant clinical signs of pneumonia and two animals died due to bovine herpesvirus-1 infection.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

15.
Septicemic pasteurellosis (SP) was induced in feedlot lambs. Twenty-eight lambs, randomly allotted into 7 groups, were given combinations of 3 treatments: (i) immunosuppression using hydrocortisone solubilized in dimethyl sulfoxide, (ii) rapid changes in feed, from 100% roughage to 90% concentrate, and (iii) oral inoculation of Pasteurella haemolytica biotype T. Feed changes and immunosuppression by hydrocortisone were needed for the production of SP. Pasteurella haemolytica inoculation was not necessary for induction of SP in all cases, indicating an endogenous source of infection. Clinical pathologic, bacteriologic, and gross and microscopic pathologic findings of induced SP were similar to those described for naturally occurring SP in lambs. Infection of lambs with P haemolytica biotype T via the gastrointestinal tract is discussed as a possible step in the pathogenesis of SP in feedlot lambs.  相似文献   

16.
A survey of antibody to Pasteurella haemolytica and P multocida, using a fluorometric immunoassay, was conducted on sera collected from 264 dairy cattle from 3 herds. Serum antibody titers to P haemolytica were 0 to 270 with low titers (less than 25) seen in 48.1% of the cows and heifers. Serum antibody titers to P multocida were 0 to 380 and the frequency of distribution of these titers were more even than for P haemolytica. Mean serum antibody titers to P haemolytica were significantly (P less than 0.005) higher in cattle from an open dairy herd when compared with those from 2 closed herds. Antibody titers to these organisms was determined in 7 colostrum samples. Pasteurella haemolytica antibody titers varied, depending on the whey separation technique used. Passive transfer of colostrum-derived antibody in 5 neonatal calves resulted in a maximum mean serum antibody titer at 20 hours after birth for P haemolytica and at 8 hours after birth for P multocida. Serum titers were higher overall for P multocida than for P haemolytica. Serum titers for P haemolytica declined rapidly. A significant (P less than 0.05) increase in antibody to P multocida was observed at 5 days of age.  相似文献   

17.
A commercially available microbiological identification system and DNA:DNA hybridization were used to determine relationships between and within serovars 1-13 of Pasteurella haemolytica, and between P haemolytica and P multocida and 4 species of Actinobacillus. All serovars of P haemolytica that belonged to biovar A were related with mean DNA homology of 78%, whereas all serovars of P haemolytica that belonged to biovar T were related to each other with mean DNA homology of 90%. The DNA:DNA hybridization between strains of biovars A and T ranged from 3 to 13%, indicating little or no genetic relationship between the 2 biovars of P haemolytica. The DNA homology between all serovars of P haemolytica and other species of non-P haemolytica bacteria tested (P multocida and actinobacilli) was less than 14%, suggestive of essentially no genetic relationship of P haemolytica with the ATCC reference strains of the genus Pasteurella or the genus Actinobacillus. Enzymatic differences were observed between P haemolytica and the other non-P haemolytica bacteria tested; however, the microbiological identification system that uses enzymatic reactions could not distinguish among biovars of P haemolytica. Results of this research support other data that suggest that biovars A and T of P haemolytica should be classified as separate species, but do not support the inclusion of either biovar A or T within the genus Actinobacillus.  相似文献   

18.
Pasteurella haemolytica serovars 1 through 12, grown in broth and on agar plates, and 2 field isolates (types A1 and T10) were used to develop polyvalent crossed immunoelectrophoresis (XIE) reference systems. The maximal number of antigens was revealed by XIE when sonicates of agar plate-grown organisms were used as the immunogen (to produce antibodies) and as the soluble antigen for XIE. Antigens produced from agar plate-grown organisms were less contaminated (by antigenic components of the medium) than were those produced from organisms grown in broth. Seventy-two antigens were detected in sonicated preparations of agar plate-grown P haemolytica. The common antigen of gram-negative bacteria was identified in the P haemolytica XIE reference system; precipitation was observed with rabbit antiserum to the common antigen of gram-negative bacteria isolated from Escherichia coli, as well as with rabbit immunoglobulins (obtained from unvaccinated rabbits). Most preimmune sera from our vaccinated rabbits also precipitated the common antigen. Serovar-specific antigens in the P haemolytica XIE reference system were defined and presumptively identified as part of the bacterial lipopolysaccharide complex by use of the limulus amebocyte lysate test. Partial cross-reactions were found between serovar-specific antigens within each biovar (A and T). Pasteurella haemolytica biovar A-specific and biovar T-specific antigens were defined by crossed-line immunoelectrophoresis. When serovars A13, A14, and T15 were tested in the P haemolytica XIE reference system, they gave high matching coefficient values of 0.98, 0.98, and 0.87, respectively. The proposal to separate P haemolytica biovars A and T into 2 different species was supported by immunotaxonomic data obtained from crossed immunoelectrophoresis, but more extensive studies will be necessary to establish the appropriate taxonomic position of these 2 groups of organisms.  相似文献   

19.
Toxin neutralizing activity of bovine sera and body fluids against Pasteurella haemolytica type A1 cytotoxin was evaluated by 51Cr release assay using bovine peripheral blood mononuclear leukocytes as the target cells. Sera collected from precolostral calves did not exert anticytotoxin activity at 10(-1) or higher dilutions, whereas randomly selected complement fixing antibody-negative sera neutralized on average over 90% of cytotoxin activity at the 10(-1) dilution and less than 50% of the toxin activity at 10(-2) or higher serum dilutions. Nasal secretions and lung washings of some of the cattle tested also contained cytotoxin neutralizing activity. The antibody nature of the cytotoxin neutralizing activity was demonstrated by its neutralization with bovine immunoglobulin G2 purified from pooled seropositive sera. Sera from a group of cattle which were vaccinated with a potassium thiocyanate extract of P. haemolytica, but which subsequently developed fibrinous pneumonia after aerosol challenge with bovine herpesvirus 1 and P. haemolytica, had significantly lower anticytotoxin activity than sera from another group of cattle which did not develop the disease after similar vaccination and challenge. Cattle which survived a natural outbreak of shipping fever had higher anticytotoxin activity than those having fibrinous pneumonia in the aforementioned experimental group, although there was no statistical difference between them and a randomly selected CF seronegative group. It is probable that this cytotoxin neutralizing antibody exerts a beneficial effect in protection of cattle against pneumonic pasteurellosis.  相似文献   

20.
A field trial compared a modified Pasteurella haemolytica biotype A serotype 1 leukotoxin vaccine to a commercial vaccine during March-July 1995 in a Natal Midlands, South African, feedlot. Weaners/long weaners purchased by the feedlot were allocated systematically into test vaccine and control vaccine groups of 1241 and 1240 head, respectively, and fed in groups of approximately 200 head. Morbidity and mortality were monitored until the animals were marketed. Details of pleuritis and pneumonia at veterinary meat inspection were recorded for 409 test-vaccinated and 424 control-vaccinated cattle. An increase in morbidity but not mortality risk of respiratory disease was shown between test (13.8% morbidity) and control (11.4% morbidity) groups. Cattle with a processing weight <245 kg were 1.4 times more likely to develop respiratory diseases than cattle with a processing weight > or =245 kg. Cattle bought on auction were 1.6 times more likely to develop respiratory disease than cattle bought at private sales. A partial farm budget incorporating Latin Hypercube sampling of uncertain variables was done to obtain the distribution of possible financial outcomes if the test vaccine were used. Impact (sensitivity) analyses indicated that median weight of carcass cut away had the greatest impact on the profit margin. The partial farm budget highlighted the importance of reducing sub-clinical lesions in a feedlot.  相似文献   

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