Bacteria in CF Lung Infections Is Same in Chronic Rhinosinusitis

Less diverse microbiota linked to more severe symptoms of disease

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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The bacteria that causes chronic rhinosinusitis — swelling of the nasal cavity and sinuses — in people with cystic fibrosis (CF) are also those that often seed infections in their lungs, which means preventing or treating sinus disease may help better manage the symptoms of CF, a study suggests.

Researchers also observed that while there were more Pseudomonas aeruginosa or Staphylococcus bacteria over other types of germs, their amounts varied over time. And the less diverse the sinus microbiota, the worse the symptoms of chronic rhinosinusitis and CF. The sinus microbiota refers to the collection of all germs living in the sinuses, which are air-filled pockets in the head.

“As therapeutic options for CF are expanded and life expectancy extended, a comprehensive understanding of the ecological and evolutionary drivers of CF sinus disease holds promise for more rational interventions and treatment of chronic respiratory infections in people with CF,” the researchers wrote.

The study, “Low diversity and instability of the sinus microbiota over time in adults with cystic fibrosis,” was published in Microbiology Spectrum.

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Better Diagnosis, Treatment Needed for Chronic Rhinosinusitis in CF Care

The nose, mouth, and throat are exposed to germs all the time. When these germs enter and settle in the sinuses, which can occur after a cold or flu, they can cause swelling. The swelling usually clears up on its own as the germs are flushed away by the mucus made by the sinuses.

But in people with CF, the mucus becomes thick and sticky, and it may trap the germs instead of helping get rid of them. This means swelling can take longer to go away.

Chronic rhinosinusitis occurs when the sinuses keep getting infected and inflamed. When this happens, it brings about nasal congestion (a blocked nose), pain and tenderness around the cheeks and eyes, a headache, and a reduced sense of smell.

While chronic rhinosinusitis is common and can make for a poor quality of life for CF patients, how it tracks with disease symptoms is not exactly known. Researchers in the U.S. explored the idea that the type and number of germs that make up the sinus microbiota may point to how severe the disease is.

Sinus swabs hint at disease severity

To identify which bacteria were present in samples of sinus swabs, they used a method called 16S rRNA sequencing. The samples came from 27 adults with CF who also had chronic rhinosinusitis.

Their median age was 27.6 and one-third (33.3%) were men. Most (81.5%) used topical antibiotics to treat their sinuses and many (77.7%) were taking topical or oral steroids. Ten (37%) patients were taking CFTR modulators, which target the root cause of CF.

All sinus swabs were collected during clinic visits. For nine patients, there was just one sinus swab available. Two or more sinus swabs (up to 10) were collected over a median 522 days (almost 1.5 years) for the remaining 18 patients.

Of a total of 302 types of bacteria the team identified, two stood out as the most predominant types — P. aeruginosa (a main type of bacteria causing CF lung disease) and Staphylococcus — while other types were present in low amounts. But their abundance varied across samples from the same patient, showing the importance of collecting many samples over time, the researchers said.

The researchers also identified bacteria sometimes present in drinkable water. “The presence of bacteria frequently reported to be present in potable water suggests a potential exposure route of the sinuses to opportunistically pathogenic microbes,” they wrote.

Under a microscope, the team saw that both P. aeruginosa and Staphylococcus aureus lived as small communities close to cells of the sinuses. These communities also hosted small numbers of other types of bacteria.

The presence of more Pseudomonas bacteria was linked to CF-related diabetes, a common symptom of CF, while the presence of more of Staphylococcus bacteria was linked to sinus exacerbation, defined as a worsening of chronic rhinosinusitis symptoms and/or an unscheduled visit. It’s known to be linked to an increased odds of having a lung exacerbation, or worsening lung function.

When a patient had a sinus exacerbation, the sinus microbiota was not as diverse, “suggesting that a more diverse sinus microbiota, not dominated by one or very few taxa [groups of bacteria], is associated with less severe sinus disease,” the researchers wrote.

The least diverse the sinus microbiota, the more the inflammation, including higher levels of an inflammatory protein called interleukin-1beta (IL-1beta) that was linked to more damage to the sinuses.

“These findings suggest that sinus inflammation is highest when microbial community diversity is low,” the researchers wrote, adding that they provide “support for investigation of therapeutic strategies targeting [IL-1beta] for CF sinus disease” and reinforces research that establishes “the sinuses as an important site of chronic infection.”

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