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Cystic Fibrosis Aggregate Biofilm Model to Study Infection-relevant Gene Expression
Published on: April 18, 2025
Group B streptococcus (GBS) is an important pathogen in human disease- but what about in cystic fibrosis?
Kate Skolnik1,2, Austin Nguyen3, Christina S Thornton3
1Department of Medicine, University of Calgary, 7007 14th Street SW, Calgary, AB, T2V 1P9, Canada. kate.skolnik@albertahealthservices.ca.
Background:
Group B Streptococcus (GBS) is a common commensal capable of causing severe invasive infections. Most GBS infections occur in neonates (often as pneumonia). GBS can also cause infection in adults with diabetes and other immunological impairments but rarely leads to pneumonia in adults. GBS has occasionally been found in the sputum of Cystic Fibrosis (CF) patients, an inherited condition known for progressive lung disease. However, the epidemiology and clinical significance of GBS in CF are not understood.
Methods:
We retrospectively reviewed a large single-centre adult CF population with an associated comprehensive, prospectively collected bacterial biobank beginning in 1978. We identified all individuals with GBS isolated from their sputum on at least one occasion. The primary outcome was risk of pulmonary exacerbation (PEx) at the time of the first GBS isolate compared to the preceding visit. Secondary outcomes included determining: prevalence of GBS infection in a CF population, whether GBS infections where transient or persistent, whether GBS strains were shared among patients, change in % predicted FEV1 at the time of GBS isolate compared to the preceding visit, PEx frequency after the first GBS isolate, change in % predicted FEV1 after the first GBS isolate, and complications of GBS infection.
Results:
GBS was uncommon, infecting 3.5% (11/318) adults within our cohort. Only three individuals developed persistent GBS infection, all lasting > 12 months. There were no shared GBS strains among patients. PEx risk was not increased at initial GBS isolation (RR 5.0, CI 0.69-36.1, p=0.10). In the two years preceding initial GBS isolation compared to the two following years, there was no difference in PEx frequency (median 2, range 0-4 vs 1, range 0 to 5, respectively, p=0.42) or lung function decline, as measured by % predicted FEV1, (median -1.0%, range -19 to 7% vs median -6.0%, range -18 to 22%, p=0.86). There were no invasive GBS infections.
Conclusion:
In adults with CF, GBS is uncommon and is generally a transient colonizer of the lower airways. Despite the presence of structural lung disease and impaired innate immunity in CF, incident GBS infection did not increase PEx risk, PEx frequency, rate of lung function decline, or other adverse clinical outcomes.
Insights
Group B Streptococcus (GBS) is uncommon in adults with Cystic Fibrosis (CF) and typically colonizes airways temporarily. GBS infection in CF patients did not increase pulmonary exacerbation risk or lung function decline.
Area of Science:
- Pulmonary Medicine
- Infectious Diseases
- Microbiology
Background:
- Group B Streptococcus (GBS) is a common bacterium causing severe infections, particularly in neonates.
- While GBS can infect adults with compromised immunity, it rarely causes pneumonia.
- GBS has been observed in Cystic Fibrosis (CF) patients, but its prevalence and clinical impact in this population are unclear.
Purpose of the Study:
- To investigate the epidemiology and clinical significance of Group B Streptococcus (GBS) in adult Cystic Fibrosis (CF) patients.
- To determine if GBS colonization or infection is associated with increased pulmonary exacerbations (PEx) or lung function decline in CF.
Main Methods:
- Retrospective review of a large adult CF cohort with a bacterial biobank starting in 1978.
- Identification of patients with GBS isolated from sputum.
- Analysis of primary outcome: risk of PEx at initial GBS isolation versus preceding visit.
- Secondary outcomes included GBS prevalence, persistence, strain sharing, and impact on lung function (% predicted FEV1).
Main Results:
- GBS was uncommon, found in 3.5% of the adult CF cohort.
- Most GBS infections were transient; only three patients had persistent infections (>12 months).
- No increased risk of PEx at initial GBS isolation (RR 5.0, p=0.10) or changes in PEx frequency and lung function decline were observed.
Conclusions:
- In adult CF patients, GBS is an uncommon and generally transient colonizer of the lower airways.
- Incident GBS infection did not elevate PEx risk, PEx frequency, lung function decline, or other adverse clinical outcomes in this population.
- These findings suggest GBS has a limited clinical impact in adult CF patients despite underlying lung disease and immune impairment.
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