Functional and metabolic interactions of bovine alveolar macrophages with Pasteurella haemolytica (biotype A, serotype 1) and possible bacterial extrachromosomal genetic factors responsible for virulence.
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| Format: | Thesis Book |
| Language: | English |
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1984.
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| Online Access: | Link to ProQuest Copy Link to OAKTrust copy |
| Abstract: | Pasteurella haemolytica is generally recognized as the most economically important infectious agent involved in the bovine respiratory disease complex (BRDC). Alveolar macrophages (AMO) are a primary mechanism of pulmonary host defense against bacterial sepsis at the level of the alveoli. If P haemolytica is to establish a nidus of infection in the bovine lung then the organism must overwhelm or circumvent the AMO host defense system. A luminol-dependent chemiluminescence (LDCL) assay was developed for the study of the interaction of pathogenic (P haemolytica biotype A, serotype 1) and nonpathogenic (Escherichia coli K-12) bacteria with bovine AMO (BAMO) in pulmonary lavage cells (PLC). Efficient LDCL was produced by PLC phagocytically stimulated with E coli. The LDCL profile was characterized by a rapid rise to a peak at 60 min followed by a gradual decline in the next 60 min and then relative stability above control values for the remaining 60 min of the incubation period. In contrast the LDCL profile induced by P haemolytica was characterized by an extremely rapid rise in LDCL in the early stages after phagocytic stimulation followed by a precipitous decline and subsequent total cessation of LDCL. Kinetics of the LDCL response to living and heat-killed P haemolytica in LDCL, ('51)chromium release, and macrophage bactericidal assays. Collectively, the results suggested that living P haemolytica cells possess a heat-labile cytotoxic factor that functionally incapacitates BAMO and thereby reduces the antimicrobial effectiveness of an important pulmonary host defense mechanism.Basic aspects of P haemolytica biology were studied in relation to plasmid and inducible bacteriophage content. A bacteriophage was induced from all isolates and kinetics of induction and bacteriophage morphology were determined. Isolates of P haemolytica contained either 0, 2, or 3 apparent plasmids. The presence of plasmids were related to antibiotic resistance to ampicillin and penicillin, but not related to cytotoxic activity. P haemolytica cytotoxic factor appears to be coded for on the bacterial chromosome. |
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| Item Description: | "Major subject: Veterinary Microbiology and Parasitology." Typescript (photocopy). Vita. |
| Physical Description: | xiv, 138 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 125-137). |