Relatives with CF Can Be Source of MRSA Transmission, Study Finds
Among people with cystic fibrosis (CF), antibiotic-resistant Staphylococcus aureus is sometimes transmitted among relatives, but rarely in healthcare settings, an analysis of patients at a CF center in Iowa suggested.
Findings also indicate that distinct subsets of S. aureus may be associated with differences in disease progression.
These results were in the study, “MRSA Strains with Distinct Accessory Genes Predominate at Different Ages in Cystic Fibrosis,” published in the journal Pediatric Pulmonology.
S. aureus is a bacteria that can cause lung infections in people with CF. Methicillin-resistant S. aureus, or MRSA, is a variety of this bacteria and, as its name suggests, is resistant to treatment with the antibiotic methicillin.
A team of researchers at the University of Iowa reported an increase in MRSA infections among CF patients at their institution.
“We suspected that rising MRSA prevalence over the past decade may have been hastened by either person‐to‐person or healthcare worker‐to‐patient transmission,” they wrote.
To test this idea, the scientists sequenced the genomes (genetic code) of 97 MRSA isolates collected from 74 patients attending either the university’s pediatric or adult CF clinic in 2017. By comparing genetic sequences among the different isolates, the researchers could look for clues as to how the bacteria were transmitted.
In general, bacteria with relatively similar sequences are more closely related to each other. As such, if two people have MRSA isolates with very similar sequences, it is probable that one person acquired the infection from the other.
Analysis showed evidence of MRSA transmission between relatives — for example, between a parent and their child, or between siblings. However, instances of related individuals with distinctly different MRSA strains were also noted.
In contrast, results showed minimal evidence suggesting transmission within hospitals, which indicates that these infections probably are not being acquired in a healthcare setting.
Investigators then further analyzed the bacterial genomes. Specifically, the team conducted a cluster analysis — which involves grouping the genomes into “clusters,” based on similarities and differences in the genetic code.
They created three clusters, termed A, B, and C. Most of the CF patients had MRSA in either cluster A or cluster B.
Patients infected with cluster A bacteria tended to be older, whereas all but one patient with cluster B bacteria was younger than 20. Further analysis of people under age 20 suggested that young patients infected with cluster A tend to have poorer lung function, and a faster rate of lung decline than those with cluster B.
“Although these differences in outcomes between MRSA clusters were intriguing, they require confirmation in larger studies,” the researchers wrote.
This study is limited by being conducted at a single institution and by a design that precluded analysis of whether differences in pulmonary function are due to the type of MRSA, the team noted.
“Understanding the origins of MRSA in patients with CF could help limit acquisition of these resistant bacteria and improve patient outcomes,” the scientists concluded.