Hispanic CF patients in US at higher risk of lung infections:…

Hispanic cystic fibrosis (CF) patients are at a higher risk of developing Staphylococcus aureus lung infections — and at a younger age — than are non-Hispanic white patients, according to a new U.S. study.

The analysis also indicated that Hispanic CF patients, on average, develop both antibiotic-responsive and antibiotic-resistant S. aureus infections earlier in life.

Scientists believe it is possible that this increased exposure might contribute to the relatively more severe lung function declines that are observed among Hispanic CF patients relative to their non-Hispanic counterparts.

“These are significant findings as it means Hispanic [people with] CF have more years of S. aureus exposure and, in turn, more years of chronic inflammation,” the researchers wrote, noting that “chronic pulmonary inflammation in CF leads to structural lung damage … and lower pulmonary function even early in life.”

The study, “Ethnic differences in staphylococcus aureus acquisition in cystic fibrosis,” was published in the Journal of Cystic Fibrosis.

Investigating the role of S. aureus infections in lung function

Although CF is most prevalent among Caucasians, the genetic disease can affect people of all races and ethnicities. Data indicate that neither the symptoms nor progression of CF are uniform across ethnic groups.

Particularly, Hispanic CF patients have been found to have lower lung function and be at a higher risk of death relative to white, non-Hispanic patients.

The reasons underlying this difference are not known, but it is possible that lung infections might play a role, according to researchers. Infections with bacteria such as Pseudomonas aeruginosa — previously found to be a major contributor to lung disease in people with CF — are known to negatively affect lung function and survival of CF patients.

Indeed, Hispanic patients are at a higher risk of acquiring P. aeruginosa lung infections than their Caucasian counterparts. These infections also occur at an earlier age and are more likely to become chronic or drug-resistant in Hispanic patients.

S. aureus, another common infection-causing bacteria in CF, has shown a dramatic increase in prevalence among CF patients in recent years. Like P. aeruginosa, it is linked to lung function declines and mortality risk, particularly for antibiotic-resistant strains.

Now, a team of scientists aimed to more closely examine whether the acquisition of S. aureus infections early in life differs between Hispanic and non-Hispanic white patients in the U.S.

“Our study [is] the first longitudinal investigation of ethnic differences in S. aureus in [people with] CF to our knowledge,” the scientists wrote.

Long-term clinical data were assessed from 797 Hispanic people and 9,843 non-Hispanic individuals included in the U.S. Cystic Fibrosis Foundation Patient Registry (CFFPR) between 2008 and 2013. All of the patients were younger than 25.

With clinical information for more than 80% of CF patients in the U.S., the CFFPR is the largest database of Hispanic CF patients. Data from each patient were analyzed up to the year 2018 or age 25.

Lung infections found to occur 1 year earlier in Hispanic children with CF

The results from this analysis indicated that Hispanic patients first had antibiotic-sensitive S. aureus infections — also called Methicillin-sensitive Staphylococcus aureus or MSSA — significantly earlier than did non-Hispanic patients. Specifically, Hispanic children acquired such infections at a median age of 3.8 years compared with 4.9 years for white youngsters.

Likewise, antibiotic-resistant infections — also called Methicillin-resistant Staphylococcus aureus or MRSA — occurred sooner in Hispanic patients. The median for Hispanic patients was 20.8, compared with 22.4 in the non-Hispanic group.

Acquiring S. aureus years earlier, even if just intermittently, may contribute to more severe pulmonary function by age six years and higher mortality.

After adjusting for clinical, biological, and socioeconomic factors, Hispanic patients were found to be about 18% more likely to experience MSSA than non-Hispanic patients.

While they also were found to be at an elevated risk of MRSA in initial analyses, that difference was not maintained after adjusting for both clinical and socioeconomic factors.

At the age of 2.5 years, Hispanic children were at a significantly higher risk of acquiring an MSSA infection than were non-Hispanic patients. By age 10, these children also were at a significantly elevated risk of MRSA.

The risk of persistent MRSA infections, defined as three or more positive tests for MRSA during follow-up, was not increased in Hispanic patients at any age.

“Acquiring S. aureus years earlier, even if just intermittently, may contribute to more severe pulmonary function by age six years and higher mortality,” the researchers wrote.

Data in study predates use of CFTR modulator therapies

The researchers noted that, while Hispanic patients did have more yearly cultures to test for the infection, that alone was unlikely to explain the significant differences in S. aureus acquisition.

The team also pointed out that the data were collected prior to the widespread use of CFTR modulator therapies for treating the disease. CFTR modulators are a newer class of medication that have been found to ease CF symptoms and slow disease progression.

While these therapies have drastically affected outcomes for CF patients, including a reduced risk of lung infections, Hispanic patients and those from other minority groups are less likely to be eligible for them than are Caucasian patients, studies have shown. Indeed, one 2021 study found U.S. patients from racial and ethnic minority groups in the U.S. are two times more likely to be ineligible than white individuals.

As such, the scientists believe the differences observed in the study could possibly be even more dramatic if data from more recent years had been included.

“Further studies are needed to understand how MSSA and MRSA independently contribute to the observed disparities in pulmonary function in Hispanic [CF patients],” the team wrote.

Such studies also should include Black CF patients, who have similarly been found to be at an increased risk for poor outcomes, according to the authors.