2 Anaerobic Bacteria Species Tied to Declining Lung Health in Adults
Two types of bacteria — Porphyromonas pasteri and Prevotella nanceiensis — were found to be highly prevalent in the mucus of adults with cystic fibrosis (CF) and associated with a progressive decline in lung health, a study reported.
These two bacteria differ from previously identified, disease-exacerbating bacteria in being anaerobic species, meaning they do not require oxygen to survive.
“Our findings support a potential association of specific anaerobic species abundantly present in CF [mucus] with long-term lung function decline,” the researchers wrote.
The study, “Porphyromonas pasteri and Prevotella nanceiensis in the sputum microbiota are associated with increased decline in lung function in individuals with cystic fibrosis,” was published in the Journal of Medical Microbiology.
Lung infections are common in CF and associated with lung damage. Several species of aerobic bacteria, which require oxygen to survive, have been shown to cause airway infections in these patients.
Anaerobic bacteria, which live without oxygen, are also frequently present in CF airways, but few studies have investigated whether they contribute to disease progression.
Researchers in the U.K. evaluated anaerobic bacteria in CF sputum — a mixture of saliva and mucus from the lungs — and its potential association with lung function decline over eight years.
“We hypothesized that the presence and relative abundance of the most prevalent, live, anaerobic bacteria in sputum of adults with CF were associated with adverse clinical outcomes,” the researchers wrote.
Sputum samples from 70 adults with CF (median age of 30.6) who had been recruited at CF centers in the U.K. for a previous study were analyzed and compared with patients’ clinical data.
Among the 10 most abundant anaerobic bacteria in the samples, P. pasteri and P. nanceiensis alone were associated with lung function declines, as measured by yearly changes in each patient’s forced expiratory volume (FEV), the amount of air a person can exhale in one breath.
Data showed the presence of P. pasteri or P. nanceiensis correlated with an average FEV loss of 52.3 and 67.9 milliliters each year, respectively, indicating a decline in lung health. The greater the abundance of either bacteria in an individual’s sample, the faster the rate of decline.
P. pasteri was observed in 21 of these 70 adults (30%), and P. nanceiensis in nine (12.9%).
Of note, 68 patients (97.1%) had chronic Pseudomonas aeruginosa infection, the aerobic bacteria most often associated with CF lung infections.
P. aeruginosa and the two anaerobic species might collaborate to contribute to lung decline, the researchers wrote. This idea is supported by previous research suggesting that anaerobic and aerobic bacteria work together to cause inflammation in CF.
The researches also noted that studies in children reported a protective effect for the Porphyromonas species, including a defense against P. aeruginosa. These conflicting results, they suggested, could be due to the wide diversity of aerobic and anaerobic bacteria present and interacting with one another at any given time.
“This suggests that diverse anaerobic species present in the airway may have distinct pathogenic [disease-causing] or protective roles depending on individual interactions in the lung,” the researchers wrote.
They also noted that their work was in “adults with chronic pulmonary P. aeruginosa and more severe pulmonary disease,” unlike the pediatric studies.
A study limitation was the one-time collection of sputum samples at its start, and compared with data on clinical overcomes over eight years. Changes in the bacteria were not assessed over time. Future studies should address this through regular sample analysis, the researchers noted.
Still, “our findings support a potential association of specific anaerobic species abundantly present in CF sputum with long-term lung function decline,” the team concluded, and “suggest that Prevotella and Porphyromonas species may contribute to lung disease and CF” progression.