Cystic fibrosis and the effects of a microbial community

By Ramiro Bustamante Torres, April 4 2023—

A paper published in January 2023 from the University of Calgary had challenged previous ideas about the human lung and the microbial community. The main author of the paper, Dr. Christina Thornton, is an assistant professor in the Department of Medicine and the Department of Microbiology, Immunology and Infectious Diseases — she is also a respirologist and clinician scientist — at the Cumming School of Medicine. As a respirologist, she specializes in cystic fibrosis and her research focuses on the microbiological aspect of the disease.

Cystic fibrosis is a genetic disease that can affect the lungs, digestive system and reproductive system. According to Cystic Fibrosis Canada, one in 25 Canadians carry a defective copy of the gene responsible for cystic fibrosis. Previously, it was believed that infections in patients with cystic fibrosis were caused by single organisms in the lungs but Thornton has found that the microbial community of a patient’s lung has a major impact on their health and treatment. 

“The way I kind of like to talk about it is as lung disease gets worse, meaning you’re starting to reach the point of either needing a lung transplant or potentially passing away from the disease, your microbial community in the lungs tends to become less diverse,” said Thornton. “You want to have a rich community, you want to have lots of different bacteria there because they do things like protect against the bad bacteria, they provide sort of a good environment for the immune system. But we know that as patients get worse in their disease, that community tends not to be so diverse, and it tends to be overtaken by one of a few bad bacteria.”

Thornton mentioned that patients with a lower lung function were considered to have a low diversity in their lung microbial community. In previous research, she had worked with Dr. John LiPuma from the University of Michigan who had sputum samples — the inner mucous material in the lungs — dating back to the 90s up to 2022, which allowed them see the microbial community changes for patients at different lung capacities over time.

“We found patients that were all end-stage — their lung function was less than 40 per cent. We found that while there were about 60 per cent that did have that traditional kind of community that’s dominated by one of those bad bacteria,” said Thornton. “We surprisingly found nearly half or 40 per cent weren’t. In fact, they were quite diverse. We found that those people that had more diverse communities actually did better. They had less need for transplantation, less death, less exacerbations. And the reason this study was unique is that is not typically what’s thought of with end stage disease.”

When talking about her recent publication, Thornton had stated that there was a difference in infection expectancies depending on the bad bacteria that has dominated the microbial community. Three genus were specified in her research — the Burkholderia genus, Pseudomonas genus and Staphylococcus genus. She mentioned that in the past, children were taken to cystic fibrosis camps where they could interact with other children with the disease to socialize. Unfortunately, many children died due to the camps as they were infected with Burkholderia which is highly transmissible and highly virulent. She goes on to say that there is a trajectory that can be followed depending on the pathogen dominating the microbial community.

“In our study, Burkholderia was absolutely the worst, it was just under two years to needing a transplant or death after you acquired it. Pseudomonas was longer with several years, and Staphylococcus was actually the best,” said Thornton. “Even though these are all pathogens, it just goes to show even amongst them, there’s quite a bit of diversity.” 

As a respirologist, Thornton shared how she and her colleagues have worked together towards creating personalized medicine for their patients with cystic fibrosis. She says that seeing a patient at a later stage of cystic fibrosis with a more diverse community can avoid getting a transplant which could cause many side effects compared to a patient with a dominant community in their system. 

“We’re taught this disease is this, and it’s very homogenous across patients, and that’s just not true,” said Thornton. “The goal of any clinician scientist is to bridge the bench to the bedside. That’s always our goal. And I think this helps give us information that we can hopefully start to apply to our patients.”

To know more about Thornton’s research, you can find her U of C profile here. 

“In medicine, just like science, always be inquisitive. Things that we take as dogma or things that we take that this is the way it is, be inquisitive about it, because you might find that so-called standards are not necessarily the case,” said Thornton.