In many cases, it is unclear whether recovery of the organism from sputum or BAL fluid represents colonization or true infection. In our patient, the organism was present on specimens from transbronchial biopsy, protected brushing, and BAL, which indicates that it represented a true pathogen. Infection occurs via contact with infected animals; however, there are many cases, including fatal ones, that have been reported where no animal contact was identified. Our patient’s bronchiectasis, which has been linked to other pulmonary infections, may have predisposed him to B bronchiseptica pneumonia, although there is no known association. Cases of B bronchiseptica have also been reported in patients with cystic fibrosis and with emphysema, raising the possibility that preexisting lung disease, especially one that causes structural changes to the lung, may be associated with infection.