Although the presence of virus or bacteria, or their combination, is associated with acute exacerbations in bronchiectasis patients, each of these microbes is linked to differing symptoms, a study found.
These distinctions might be useful to physicians in identifying which microbes are causing a flare and in optimizing treatment plans, its scientists reported.
The study, “The Roles of Bacteria and Viruses in Bronchiectasis Exacerbation: A Prospective Study,” was published in the journal Archivos de Bronconeumología.
In bronchiectasis, the bronchi or small lung airways become inflamed, and progressively larger and thicker due to bacterial and/or viral infections.
These recurrent or chronic respiratory infections are often linked to acute exacerbations, and associate with more severe symptoms and poorer lung function.
Although the individual roles of bacteria and viruses have been addressed in people with bronchiectasis, studies have not investigated the impact both types of microbes on patients, or fully assessed symptoms that help differentiate bacterial from viral infections.
To investigate the relationship between acute flares and the presence of these microbes, researchers in China and Spain analyzed the composition of sputum samples (mucus expelled by coughing) from 108 adults with bronchiectasis, with an average age of 46.8. Of them, 98 patients were followed over a median of 13 months.
All were examined at outpatient clinics of The First Affiliated Hospital of Guangzhou Medical University in China, every three to six months, between March 2017 and November 2018.
Sputum samples collected during this period were divided in two batches to be analyzed separately for their viral and bacterial content. At initial visits, the investigators also collected information from flares occurring in the year prior to the study’s start. Symptoms and lung function were also evaluated during acute exacerbations.
Most of the 98 patients (74.5%) being followed had at least one acute exacerbation during the 13 months for a total of 169 flares.
The presence of bacteria in sputum samples was not associated with acute exacerbations. Viruses were isolated 3.28 times more often when patients were having flares, particularly rhinovirus and influenza.
New bacteria and mixed populations of viruses and bacteria were more than twice as frequent in sputum samples collected during exacerbations than in those obtained in routine visits. Notably, new bacteria sputum cultures included those that were originally negative but later found to be positive for bacteria, or those with different species of bacteria identified.
Researchers also found that the presence of each of these microbes was associated with a specific set of symptoms during acute exacerbations. While cold-like symptoms were more frequent with flares linked to viruses, severe symptoms of lower respiratory infections were more common in those whose samples had new bacteria.
Levels of the pro-inflammatory molecule interleukin-1 beta were higher in sputum samples of new bacteria collected during flares, compared with those where viruses or no microbes had been identified.
In general, patients whose sputum samples contained bacteria (with or without viruses) tended to have more severe symptoms of lower respiratory infections than those whose samples only contained viruses, the investigators found.
“Viral isolations, isolation of new bacteria and bacterial plus viral isolation are associated with bronchiectasis exacerbations. Symptoms at exacerbations might inform clinicians the possible culprit pathogens [disease-causing microbes],” the researchers wrote.
Further studies are needed to determine possible causes of acute exacerbations for which no disease-causing microbes have been identified, they added.
Study limitations included too small a number of patients to analyze specific subgroups, and an exclusion of people requiring hospitalization that may have missed cases of severe exacerbations, the team noted.
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