H. influenzae infections not tied to worse outcomes for CF adults
Bacterium has been associated with worse lung outcomes in children
Infection with an airway bacterium called Haemophilus influenzae isn’t linked with worse lung health outcomes among adults with cystic fibrosis (CF), a study suggests.
“Our study is the first to specifically dissect the natural history and consequences of H. influenzae infection in adult [people with] CF,” the researchers wrote. The study, “Clinical epidemiology and impact of Haemophilus influenzae airway infections in adults with cystic fibrosis,” was published in BMC Infectious Diseases.
Bacterial lung infections are a common problem in CF and can lead to lung function decline and pulmonary exacerbations, which is when lung function suddenly worsens, usually in the context of an infection. The bacterium H. influenzae has been linked to worse lung outcomes in children with CF, but whether this specific bacteria type is associated with worse outcomes for adults wasn’t known.
Clinical outcomes with H. influenzae infection
Researchers in Canada analyzed samples of sputum (phlegm) from 240 adults with CF who were cared for at the Calgary Adult CF Clinic between 2002 and 2016 to look for associations between H. influenzae and clinical outcomes.
Of the 240 adults tested, 70 (30%) had previously had a positive test for H. influenzae in their sputum. Among those who were positive, roughly half had more than one positive test for the bacterium and 17% had a persistent infection, meaning two or more positive samples with the same bacteria type and more than 50% sputum-culture positive for H. influenzae in each year.
Preliminary analyses seemed to suggest an association between H. influenzae and the risk of pulmonary exacerbation. But these associations weren’t seen when the researchers restricted their analysis to patients who regularly produced sputum. “Taken together, this suggests that H. influenzae recovered only at time of [pulmonary exacerbation] is more likely to come from limited sputum producers and may not accurately reflect the lower respiratory tract colonization,” the scientists wrote.
Other analyses showed no significant associations between the presence of H. influenzae in sputum and the risk of long-term lung function decline. Lung function decline was similar in patients who had long-term or short-term infections of this bacteria.
The scientists did note that patients with short-term infections tended to have higher hospitalization rates in the two years immediately after an infection compared with patients who had ongoing long-term infections. This might be due to other types of co-occurring bacterial infection, however, and may require more research, they said.
No “adverse impact associated with [H. influenzae] infection was observed on short-term or long-term outcomes,” they wrote.
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