Virulence of capsulated and noncapsulated isolates of Pasteurella multocida and their adherence to porcine respiratory tract cells and mucus

Abstract

The virulence and the adherence to porcine respiratory tract cells and mucus of three toxigenic, capsular type D Pasteurella multocida isolates and their noncapsulated variants were evaluated in the present study. Loss of capsule by P. multocida, verified by transmission electron microscopy after polycationic ferritin labeling, was associated with a massive reduction in virulence of the organisms in mice. Specific-pathogen-free piglets inoculated intranasally with one of the capsulated isolates or its noncapsulated variant developed turbinate lesions characterized by bone resorption and by an inflammation of the mucosa associated with hyperplasia and squamous metaplasia of the epithelium. Infection with the capsulated isolate led to more severe lesions and atrophy of turbinates. The interactions of these P. multocida isolates with porcine respiratory tract cells and mucus were studied in vitro. The presence of capsule resulted in a decrease in binding of respiratory tract mucus were studied in vitro. The presence of capsule resulted in a decrease in binding of respiratory tract mucus to P. multocida isolates as determined by a dot blot assay. The presence of capsule also resulted in a significant decrease in adherence to porcine tracheal rings maintained in culture. The capsule seemed to mask outer membrane components which are involved in adherence. One of these components might be lipopolysaccharide since purified lipopolysaccharide bound respiratory tract mucus and blocked adherence of this microorganism to porcine tracheal rings. Our data indicate that capsular material does not seem to be involved in adherence of P. multocida to respiratory tract cells and mucus, but capsulated isolates are more virulent in mice and also in piglets.

Adhesin–receptor interactions in Pasteurellaceae

“…Most HAP organisms can employ multiple molecular mechanisms of adherence (or multiple adhesins) to initiate infection ( Table 2). Indeed, a wide variety [112] CPS, capsular polysaccharides ; ECM, extracellular matrix ; HSP, heat shock protein; LOS, lipooligosaccharides; LPS, lipopolysaccharides; OM, outer membrane; OMP, outer membrane protein; PE, phosphatidylethanolamine; (?) role in adherence not yet established.…”

“…Lipopolysaccharides may be involved in adherence of P. multocida to porcine respiratory tract cells [112]. However, the partial inhibition of adherence to porcine tracheal rings maintained in culture by P. multocida LPS suggests that there may be non-LPS components that are also important in adherence.…”

Masquerading microbial pathogens: capsular polysaccharides mimic host-tissue molecules

“…The heparosan CPS of the animal pathogen P. multocida type D has also been demonstrated to be an important virulence factor for the organism. Acapsular variants of toxigenic P. multocida type D lose their virulence in a murine model, and lesions caused by acapsular strains are less severe than their encapsulated counterpart (Jacques et al, 1993).…”

Capsular polysaccharide expressed by Pasteurella piscicida grown in vitro

“…In this work, we demonstrated that P. piscicida, when grown in an appropriate medium, was able to produce a capsule. The capsule is notable because this structure has been reported to play a role in the pathogenicity of the virulent strains of other Pasteurella species [18,19]. Thus, the presence of this structure on the surface of P. piscicida could be a virulence factor in this microorganism.…”