Bordetella bronchiseptica Respiratory Infection Misdiagnosed as Pertussis by Multiplexed Nucleic Acid Test

Background: Bordetella bronchiseptica causes respiratory infections in animals and rarely in humans. In contrast to Bordetella pertussis, B. bronchiseptica is not susceptible to macrolide antibiotics. We report two cases of B. bronchiseptica respiratory infection initially misdiagnosed as pertussis due to a positive molecular assay, delaying appropriate therapy. 

Methods: Review of two cases of B. bronchiseptica respiratory infection and the pitfalls of using the FilmArray Respiratory Panel (FA-RP) for detection (BioFire Diagnostics, Utah). The FA-RP is a multiplexed nucleic acid test used to identify viral and bacterial pathogens including B. pertussis, but cross-reaction has been observed with B. bronchiseptica when present at concentrations above 1x10⁶CFU/mL.

Results: Case 1: 76 year-old man with diffuse large B cell lymphoma in remission and therapy-related AML who presented with fevers and productive cough. FA-RP was positive for B. pertussis and he was treated with azithromycin but remained symptomatic. His sputum culture grew B. bronchiseptica. He had no known animal exposure. He was then effectively treated with ciprofloxacin. Case 2: 52 year-old woman with AML post stem cell transplant who presented with cough. FA-RP was positive for B. pertussis and she was unsuccessfully treated with azithromycin. She was admitted due to cough, hemoptysis and fevers. Bronchoscopy with BAL was done. FA-RP on the BAL fluid was positive for B. pertussis, but culture grew B. bronchiseptica. She improved on levofloxacin. Her puppy had recently received the live attenuated Bordetella vaccine. 

Conclusion: In each case, the FA-RP detected B. pertussis in the setting of infection with B. bronchiseptica, which led to the improper choice of antibiotic therapy and delay in diagnosis. This is the first report we are aware of showing FA-RP cross-reactivity with B. bronchiseptica resulting in clinically significant outcomes. After diagnosis of pertussis by FA-RP, particularly in immunocompromised patients or those not responding to therapy, we recommend obtaining a respiratory culture to assess for B. bronchiseptica. As a medical center with an animal therapy program, these cases highlight the use of the live attenuated Bordetella vaccine in pets, resulting in policy change proposals limiting patient-animal interaction after vaccination.