title: Virulence of Bordetella parapertussis: A comparison of ovine and human isolates
Creators: name: Lund, Sarah Jane
Publisher: name: University of Glasgow
Year: 1999

description: Bordetella parapertussis is a cause of mild whooping cough in man and, in recent years, has been isolated from both healthy and pneumonic sheep. It has also been shown to interact synergistically with Pasteurella haemolytica in exacerbating ovine pasteurellosis. The relationship between ovine and human isolates of B. parapertussis has been examined at a taxonomic level and the presence of different types established. As the biological relevance of this differentiation is unknown, isolates of human and ovine origin were compared on the basis of their characteristics, including growth in ovine tracheobronchial washings (TBWs), their adherence to ovine and human cell lines and to ovine tracheal organ cultures, their interaction with ovine alveolar macrophages, their LPS production and LPS interaction with antisera. TBW are dilutions of the fluids that bathe the respiratory mucosae and are therefore the fluids in which B. parapertussis survive in vivo. This study showed that ovine B. parapertussis had the potential to grow in ovine TBW and suggested that the ability of ovine and human B. parapertussis to grow in TBW was host specific. Growth in nutrient broth also showed that human isolates grew more slowly than ovine isolates thereby suggesting that ovine and human B. parapertussis have different nutritional requirements. In the diseased host, B. parapertussis is thought to adhere specifically to ciliated respiratory epithelium. A comparison of ovine and human B. parapertussis in terms of adherence to and invasion of non-ciliated continuous cell lines showed no significant host cell preference. However, the adherence of ovine isolates to ovine tracheal organ cultures, which contain viable ciliated cells, was greater than the adherence of human isolates and therefore, the adherence of B. parapertussis to ciliated epithelial cells may be host specific. Investigation of the interaction between B. parapertussis and continuous respiratory cell lines as well as ovine alveolar macrophages revealed that the isolates which were more adherent to these cells were also more invasive. This study showed that both ovine and human B. parapertussis were capable of invasion and at least short-term survival within ovine alveolar macrophages. Analysis of the LPS produced by ovine and human B. parapertussis revealed that all the ovine isolates tested produced a rough-type LPS, whereas, the majority of human isolates had a smooth-type LPS. The exception was the human isolate NCTC 5952 which produced a pattern on PAGE similar to those of ovine B. parapertussis. The use of PAGE for LPS analysis also revealed that the choice of bacterial growth medium affected the LPS pattern visualised on silver-stained gels. Western blots of ovine and human B. parapertussis LPS with rabbit sera raised against ovine and human isolates showed that the 0-antigens of the human B. parapertussis LPS were immunodominant. These blots also showed that sera raised against an ovine isolate reacted with all the isolates tested whereas, sera raised against a human isolate reacted only with human B. parapertussis. In a bactericidal assay anti-human B. parapertussis serum killed a high proportion of human isolates but only a small percentage of ovine isolates. In comparison, anti- ovine B. parapertussis serum killed approximately the same number of ovine and human B. parapertussis. This bactericidal activity reflected the pattern of serum interaction with B. parapertussis LPS on Western blots. It may be that the LPS of B. parapertussis cells is a target for the bactericidal activity of sera. The use of LPS PAGE could not distinguish clearly between ovine and human isolates. However, the results of studies on growth, adherence to ovine tracheal organ culture and adherence to and invasion of ovine alveolar macrophages presented here strongly suggest that ovine and human B. parapertussis exhibit host-specific interactions.