INTRODUCTION: Pulmonary infections due to atypical organisms are often overlooked in immunosuppressed patients. We describe a case of Bordetella bronchiseptica infection in an immunocompromised patient.
CASE PRESENTATION: A 50-year-old man with rheumatoid arthritis, bronchiolitis, obesity and hypertension was admitted for evaluation of worsening of chronic dyspnea. His chronic dyspnea had been stable for ten years until two months prior when he noticed progressive worsening in his symptoms. At baseline, he was short of breath walking up a flight of stairs, however, now he was dyspneic walking 50 feet on flat ground. He reported a daily, non-productive cough but denied fever, chills, night sweats, weight loss, orthopnea, paroxysmal nocturnal dyspnea, and chest pain. His medications included: prednisone, sulfasalazine, leflunomide, hydrochlorothiazide, ibuprofen, omeprazole, and inhaled fluticasone/salmeterol. His occupational and exposure history was unremarkable for any known exposures to toxic chemicals or irritants. He had never smoked, drank alcohol or used illicit substances. He was married and lived with his wife and two children. They had one pet, a dog. On admission, he was afebrile with normal blood pressure and pulse and an oxygen saturation of 92% on room air at rest. Physical exam was remarkable for his obesity and markedly diminished breath sounds throughout both lung fields. Initial laboratory tests included a normal complete cell blood count, electrolytes, and renal function. Spirometry on day of admission showed a FEV1/FVC ratio of 35% and absolute FEV1 of 1.02L (23% predicted). The diffusing capacity was 68% predicted.Computed tomography of the chest showed mild bronchiectasis, mosaic appearing lung parenchyma and multiple sub-centimeter nodules throughout both lung fields. He underwent bronchoscopy to evaluate the cause of his dyspnea. Bronchoalveolar lavage (BAL), protected bronchial brushing, and transbronchial biopsies were performed. Bacterial cultures from all three grew Bordetella bronchiseptica. Treatment was initiated with levofloxacin. Subsequently, his symptoms improved markedly.
DISCUSSIONS: Bordetella bronchiseptica is a small, pleomorphic gram-negative coccobacillus. It is one of seven species of Bordetella and is a common respiratory pathogen among animals. In dogs, it causes infectious tracheobronchitis or “kennel cough.” It is believed to be the genetic ancestor to B. pertussis, the etiologic organism of “whooping cough.”(1) Bordetella species survive only for a few hours in respiratory secretions but are readily contagious. Once inhaled, the microorganism adheres to the surface of cilia and respiratory epithelial cells. Infection usually manifests itself as sinusitis, tracheobronchitis, or pneumonia. More serious infections such as acute epiglottitis, septicemia, and fatal respiratory failure have also been reported.(2) Fewer than 50 cases of B. bronchiseptica infection in humans have been reported, almost all in immunocompromised individuals. In many cases, it is unclear whether recovery of the organism from sputum or BAL represents colonization or true infection. In our patient, the organism was present on transbronchial biopsy, brushing, and BAL, which we believe indicates that it represented a true pathogen. Leflunomide and prednisone are both known to suppress immune function which predisposed him to the infection. There are no currently established guidelines for treatment of B. bronchiseptica, however, amioglycosides, anti-pseudomonal penicillins, fluoroquinolones, and tetracycline are highly effective against most isolates. Treatment includes a 2-4 week course of antibiotics, but prolonged courses, up to six months have been reported.
CONCLUSION: B. bronchiseptica is an uncommon cause of bacterial infection in humans, but can cause significant disease, particularly among those who are immunocompromised and have exposure to dogs.
DISCLOSURE: David Berkowitz, None.