Presentations

Abstract

Introduction: Bordetella bronchiseptica is a well-known pathogen that causes respiratory illnesses in dogs, rabbits, and pigs. Although it is an unusual source of human respiratory infections, it has been described in immunocompromised populations. Here we present a case of an immunocompromised patient who had B. bronchiseptica with a concurrent infection of Cryptococcus neoformans.

Case Information: A 40-year-old male with a medical history of advanced HIV and schizophrenia was admitted for altered mental status. He was found to have septic shock with hypoxic respiratory failure, and no known animal exposures. A CT Head without contrast did not reveal any acute findings. A lumbar puncture (LP) was remarkable for high opening pressure of 55cmH20 and a Cryptococcal Ag titer above 1:2560, followed by a CSF culture positive for C. neoformans. Routine blood cultures also grew C. neoformans. Induction therapy with liposomal amphotericin B and Flucytosine was started promptly and continued for 14 days. The patient had been through serial LP consecutively for 4 days, resulting in lumbar drain placement to control intracranial pressure. As 11 days of repeated post-treatment CSF culture came back without growth, treatment was transitioned to consolidation therapy with fluconazole for 8 weeks. Subsequent blood culture results (3 days after the initial blood cultures) showed no growth. A CT Chest showed multiple bilateral cavitary nodules and the patient required intubation for acute hypoxic respiratory failure. A sputum culture was positive for B. bronchiseptica and MRSA, which was later confirmed through BAL culture from bronchoscopy 2 days later. The procedure also revealed mucopurulent secretions in the mainstem bronchi bilaterally. AFB sputum tests were performed three times at least 8 hours apart, which were negative. The patient was able to wean off ventilation and extubated successfully upon treatment. He received IV vancomycin for MRSA which was switched to oral linezolid on discharge for 2 weeks. As B. bronchiseptica can cause significant disease in immunocompromised hosts, azithromycin was started. Based on sensitivity data, treatment was changed to doxycycline to complete the 2-week course. Given the patient's low CD4 count of 28 (1.7%) with undetectable viral load, Atovaquone for prophylaxis of PJP and Toxoplasma was also administered. Despite a history of non-adherence to antiretroviral therapy (ART) in the past, the patient reported taking ART and Biktarvy consistently for the past couple of months. His ART was held for 4 weeks to prevent immune reconstitution inflammatory syndrome.

Discussion/Clinical Findings: Though it is not common, there have been several cases of of human infection with B. bronchiseptica in both healthy and immunocompromised people. The infection is most common in severely immunocompromised patients including those with HIV/AIDS, malignancy, hematopoietic stem cell transplant, or solid organ transplantation. B. bronchiseptica primarily causes infection in the respiratory tract and is less likely to cause bacteremia. As this gram-negative coccobacillus mainly causes upper respiratory diseases in mammals like dogs, rabbits, rats, or pigs, animal exposure can be an important clue from history taking. Our case patient had no known recent pet or animal exposures. From a diagnostic point of view, chest imaging from B. bronchiseptica can vary from cavitary pneumonia to interstitial ground-glass opacities. Also, it can mimic the imaging of Pneumocystis jiroveci. Cavitary pneumonia by B. bronchiseptica has been described in patients living with advanced HIV, which may explain our patient's imaging. However, other possible co-infections might cause cavitary lung lesions. Firstly, this case patient is coinfected with S. aureus which also is well-known for forming necrotizing cavities. Secondly, like other fungal infections of the lungs, disseminated cryptococcosis can also cause cavitary lung lesions due to a respiratory infection. Given the three consecutively negative AFB sputum smears, pulmonary tuberculosis was felt to be less likely. Even though there are no standard antibiotics for B. Bronchiseptica, it has been successfully treated with fluoroquinolones, aminoglycosides, tetracyclines, co-trimoxazole, and piperacillin in the past. The regimen is then tailored to susceptibility testing for a total of 2-4 weeks. For our case patient, we started with azithromycin and then changed to doxycycline, which was found to be susceptible to sputum culture sensitivity results with plans for a 2-week course. Initially, we thought B. bronchiseptica could be a contaminant from sputum culture. However, his bronchoalveolar lavage also indicated the same microbe. Based on prior cases and journals, this pathogen requires prompt treatment, especially for immunocompromised patients. Previous research suggested B. bronchiseptica can be considered an HIV-related opportunistic infection. Recommendations include reducing the risk of infection from this bacteria by avoiding zoonotic exposure. However, only a few cases have focused on the actual risk of zoonosis among pet owners. To improve the diagnosis and treatment of B. bronchiseptica, future research on the risks of this population is warranted.

Conclusion: Bordetella bronchiseptica, well known for respiratory infection in mammals, can cause significant respiratory infection, especially among immunocompromised patients. Infected patients may require immediate treatment. Chest imaging can include various findings, including even cavitary lesions. Even though this particular case did not indicate exposure via animal contact, a thorough history-taking, including animal contact, can be a clue to the origins of infection.