Characterization and Time Course of Pulmonary Lesions in Calves after Intratracheal Infection with Pasteurella multocida A:3

Differences in Virulence Between Bovine-Derived Clinical Isolates of Pasteurella multocida Serotype A from the UK and the USA in a Model of Bovine Pneumonic Pasteurellosis

“…Histological examination of the lung tissues from P. multocida-challenged animals showed suppurative bronchopneumonia with or without fibrin deposits and multiple abscess formation (Fig. 2) relating to the areas of gross lesions (areas of consolidation), consistent with an airway-derived bacterial infection, and was in agreement with our previously published findings for this experimental model (Dowling et al, 2002;Dagleish et al, 2010). There was a significant (P ¼ 6.2 Â 10 À5 ) difference in the severity of lung lesions between the three groups, with calves challenged with the UK strain of P. multocida having significantly (P ¼ 0.006) greater severity of lesions compared with those challenged with the USA strain (Table 2).…”

“…Results overall indicated a much more severe clinical disease associated with the UK strain of P. multocida compared with the USA strain, and this correlated with the extensive and severe pathological lesions associated with this strain. The animals challenged with the UK P. multocida strain reproduced accurately the disease model in terms of the clinical and pathological responses observed in previous work (Dowling et al, 2002(Dowling et al, , 2004Dagleish et al, 2010). The milder clinical disease and lesser extent and severity of pulmonary lesions as a result of challenge with the USA strain of P. multocida were not due to differences in P. multocida cell numbers present within the pulmonary tissues, as both strains of bacteria were able to replicate to a similar degree.…”

“…Therefore, the differences must lie in either their direct effects on bovine tissues or host responses. It has been suggested that excessive or inappropriate host response(s) to P. multocida in bovine pneumonic pasteurellosis may be a significant factor with respect to tissue damage and, consequently, the severity of the pathology and clinical disease (Dowling et al, 2004;Dagleish et al, 2010). Subjecting the two strains of P. multocida to analysis by PFGE generated banding patterns that indicated, despite some similarities, a different overall genetic composition.…”

“…Whole BALF was filtered through sterile gauze, centrifuged at 200 g for 10 min at 4 C and serial dilutions were plated out to 10 À5 as 3 Â 20 ml aliquots to recover pure bacterial cultures of P. multocida. Samples from gross pulmonary lesions and areas of unaffected tissue were taken (approximately 1 cm 3 ) and processed to determine bacterial counts of P. multocida per gram of tissue as described previously (Dagleish et al, 2010). For histological examination, representative samples of tissue from the various lung lobes (i.e.…”

Pasteurella multocida type A as the primary agent of pneumonia and septicaemia in pigs

“…The choice of the dose was based on the results of previous experiments on pneumonia reproduction, even though they were not completely successful (Ono et al 2003, Ross 2006, Dagleish et al 2010. In these experiments, dose concentrations were usually between 10 6 to 10 9 CFU and the most successful results were achieved using the intra-tracheal route.…”