Infection with the bacterium Bordetella bronchiseptica can have varying symptoms and be difficult to eradicate in patients with non-cystic fibrosis (CF) bronchiectasis, a case series shows.
Because people, particularly those with compromised immune systems, can get this infection from animals, the researchers recommend making sure that pets are vaccinated to prevent the spread of the bacteria to humans.
The report, “Bordetella bronchiseptica in non-cystic fibrosis bronchiectasis,” was published in the journal Respiratory Medicine Case Reports.
B. bronchiseptica normally infects the respiratory tract of mammals, but infection in humans is uncommon. People taking medications that suppress the immune system, or those who have a medical condition in which their immune system is weakened, are known to be more susceptible to infection with these bacteria.
The bacteria are responsible for what’s commonly known as “kennel cough” in dogs, a hacking cough that usually disappears on its own. Humans can acquire the infection from sick pets.
Infection of B. bronchiseptica in two women and one man, all with non-CF bronchiectasis, is described in this case series. The infections were of varying degrees of severity, and infections with other species of bacteria occurred in two of the three patients.
The first patient, a 53-year-old woman, had primary ciliary dyskinesia (a rare disease that affects the tiny, hair-like structures called cilia that line the airways), and had previously had a lung infection with another bacterium — Pseudomonas aeruginosa. She complained of increased sputum production, worsening shortness of breath, and weight loss. B. bronchiseptica was isolated from her sputum, and her health improved after two weeks of treatment with the antibiotic tetracycline.
However, she then had other exacerbations (episodes of symptom worsening) over the next two years. B. bronchiseptica was repeatedly isolated from her sputum, despite extended treatments with the antibiotic doxycycline. The patient had a dog with no symptoms of kennel cough.
The second patient, a 66-year-old man, had a persistent cough with sputum production. He had previously been infected with B. bronchiseptica and another bacterium called Mycobacterium avium complex. Sputum cultures revealed the patient was infected with B. bronchiseptica and yet another species of bacteria, Staphylococcus aureus.
Treatment with antibiotics somewhat improved his condition, but the productive cough returned. Over the following weeks, other species of bacteria were isolated from his sputum. He reported owning several cats and dogs that were all in good health. However, he was then lost to follow-up, and no further information could be obtained.
The third patient was a 70-year-old woman who had previously been diagnosed with sarcoidosis and bronchiectasis. B. bronchiseptica was isolated from her sputum, but she felt fairly well and was not prescribed antibiotics. She was in frequent contact with other people’s pets, but had none of her own.
However, she required hospitalization 10 months later due to an infection with the bacterium Hemophilus influenzae that was properly treated with the antibiotic levofloxacin. The patient improved and was then discharged.
Based on the results, the researchers wrote that the clinical manifestations of B. bronchiseptica infection “can be quite variable” from apparently asymptomatic, such as in the third case, to being the sole infection, in the first case, or associated with other more usual respiratory pathogens, as in the second case.
In addition, “while the clinical presentation can be quite variable, it is important to note that Bordetella bronchiseptica can be a cause of pulmonary exacerbations and can be difficult to eradicate,” they added.
The team emphasized, however, that “whether these distinct presentations reflect differences in the host immune response to the microbe versus the expression of different virulence factors by the microbe is unknown.”
Apart from antibiotic treatment in cases of B. bronchiseptica infection, researchers also called attention to the importance of vaccinating pets and identifying infected pets to prevent zoonotic transmission — the transmission of an infectious agent to humans.
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