title: Interaction of Mycoplasma hyopneumoniae and Pasteurella multocida infections in swine.
abstract: To investigate the interaction between Mycoplasma hyopneumoniae and Pasteurella multocida infection, 32 pigs were randomly assigned by litter, sex, and weight to 4 treatment groups. Group-1 pigs were inoculated with M hyopneumoniae and allowed to recover from M hyopneumoniae infection. Group-2 pigs were vaccinated against M hyopneumoniae and then inoculated with M hyopneumoniae. Group-3 pigs were inoculated with M hyopneumoniae and developed clinical signs of mycoplasmosis. Group-4 pigs had never been exposed to M hyopneumoniae. All pigs were initially seronegative for M hyopneumoniae. All pigs were subsequently inoculated with P multocida and euthanatized 2 weeks later. Pasteurella multocida was isolated only from the lungs of group-3 pigs, and these pigs had a significantly higher median percentage of lung surface area affected by pneumonia than did pigs in the other groups. For group-3 pigs, percentage of lung surface area affected by pneumonia was positively correlated with the number of P multocida colonies isolated. We concluded that P multocida is not a primary respiratory pathogen in pigs, but that M hyopneumoniae infection can render the lungs susceptible to P multocida colonization and infection. Pigs recovered from or vaccinated against infection with M hyopneumoniae were resistant to P multocida infection.
authors.affiliation: Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Purdue University, West Lafayette, IN 47907-1248.
authors.forename: S F
authors.initials: SF
authors.lastname: Amass
authors.forename: L K
authors.initials: LK
authors.lastname: Clark
authors.forename: W G
authors.initials: WG
authors.lastname: van Alstine
authors.forename: T L
authors.initials: TL
authors.lastname: Bowersock
authors.forename: D A
authors.initials: DA
authors.lastname: Murphy
authors.forename: K E
authors.initials: KE
authors.lastname: Knox
authors.forename: S R
authors.initials: SR
authors.lastname: Albregts
mesh_terms: D000818:Animals; D008168:Lung / Q000382:microbiology; D009174:Mycoplasma / Q000276:immunology; D010326:Pasteurella Infections / Q000209:etiology / Q000276:immunology / Q000662:veterinary*; D016979:Pasteurella multocida / Q000276:immunology; D045729:Pneumonia of Swine, Mycoplasmal / Q000150:complications / Q000276:immunology / Q000662:veterinary*; D011897:Random Allocation; D013552:Swine; D013553:Swine Diseases / Q000209:etiology / Q000276:immunology; D014611:Vaccination / Q000662:veterinary