RESUMO
Bovine respiratory disease (BRD) is the most costly disease of beef cattle in North America. Because Pasteurella multocida is a commensal of the upper respiratory tract, it is generally considered an opportunistic pathogen. However, studies in swine indicated that there may be a limited number of strains associated with disease, suggesting that some are more virulent than others. Although this may also be true of isolates from cattle, appropriate typing methods must be established before this possibility can be investigated. The purpose of this study was to compare effectiveness of polymerase chain reaction (PCR) fingerprinting to more traditional approaches for typing bovine P. multocida isolates. Isolates were obtained from 41 cases of fatal BRD and subjected to random amplified polymorphic DNA PCR (RAPD-PCR), whole cell protein (WCP) profiles, outer membrane protein (OMP) profiles, and serotyping. The discrimination index was calculated for each typing method and combinations of each using Simpson's index of diversity. Correlation coefficients were calculated to assess concordance between classification results achieved through genotypic (RAPD-PCR) and phenotypic (WCP, OMP, and serotyping) approaches. All characterization methods were capable of discriminating between isolates. However, there was poor concordance between techniques. There were also few significant associations between typing results and epidemiologic data. Random amplified polymorphic DNA PCR was validated as being a repeatable and reliable means of discriminating between P. multocida isolates obtained from cattle. Isolates obtained from fatal cases of BRD in calves in a commercial feedlot demonstrated significant diversity, justifying additional investigation into whether P. multocida is a strictly opportunistic pathogen in cattle.
Assuntos
Doenças dos Bovinos/microbiologia , Infecções por Pasteurella/veterinária , Pasteurella multocida/genética , Pleuropneumonia/veterinária , Infecções Respiratórias/veterinária , Animais , Sequência de Bases , Bovinos , Doenças dos Bovinos/mortalidade , Primers do DNA , DNA Bacteriano/genética , DNA Satélite/genética , Evolução Fatal , Infecções por Pasteurella/mortalidade , Pleuropneumonia/microbiologia , Reação em Cadeia da Polimerase , Infecções Respiratórias/microbiologiaRESUMO
Pasteurella multocida OmpA (PmOmpA) belongs to the major and multifunctional Escherichia coli OmpA family of proteins. We have previously reported that the protein is conserved, immunogenic and an adhesin that binds host cells and host cell extracellular matrix molecules [Dabo SM, Confer AW, Quijano-Blas RA. Molecular and immunological characterization of Pasteurella multocida serotype A:3 OmpA: evidence of its role in P. multocida interaction with extracellular matrix molecules. Microb Pathog 2003;35(4):147-157]. In this study, we found that immunization of mice with the recombinant PmOmpA elicited strong Th2-type immune response, characterized by high immunoglobulin G(1) (IgG(1)) antibodies production. Subsequent intraperitoneal homologous challenge of the immunized mice resulted in lack of protection associated with the high IgG(1) titers in anti-rPmOmpA sera. Furthermore, the protection afforded by vaccination with P. multocida OMPs alone was adversely affected by the addition of the rPmOmpA to the vaccine preparations. The results demonstrate that PmOmpA has a detrimental effect on the efficacy of vaccination with OMPs in mice. Targeted inactivation of pmOmpA gene in P. multocida 232 represents a potential mean towards the development of an effective vaccine candidate.