Bordetella pseudohinzii as a confounding organism in murine models of pulmonary disease

A group studying acute lung injury observed an increased percentage of neutrophils in the bronchoalveolar lavage (BAL) fluid of mice. BAL was performed, and lung samples were collected sterilely from 5 C57BL/6 mice that had been bred inhouse. Pure colonies of bacteria, initially identified as Bordetella hinzii were cultured from 2 of the 5 mice which had the highest percentages of neutrophils (21% and 26%) in the BAL fluid. Subsequent sequencing of a portion of the ompA gene from this isolate demonstrated 100% homology with the published B. pseudohinzii sequence. We then selected 10 mice from the investigator's colony to determine the best test to screen for B. pseudohinzii in the facility. BAL was performed, the left lung lobe was collected for culture and PCR analysis, the right lung lobe and nasal passages were collected for histopathology, an oral swab was collected for culture, and an oral swab and fecal pellets were collected for PCR analysis. B. pseudohinzii was cultured from the oral cavity, lung, or both in 8 of the 10 mice analyzed. All 8 of these mice were fecal PCR positive for B. pseudohinzii; 7 had increased neutrophils (5% to 20%) in the BAL fluid, whereas the 8th mouse had a normal neutrophil percentage (2%). Active bronchopneumonia was not observed, but some infected mice had mild to moderate rhinitis. B. pseudohinzii appears to be a microbial agent of importance in mouse colonies that can confound pulmonary research. Commercial vendors and institutions should consider colony screening, routine reporting, and exclusion of B. pseudohinzii.