For reasons that are unclear, about 5% of patients who receive a cardiac implant develop post-operative infections. Current preventive strategies for such infections involve antibiotic therapy given in the hours and days before implantation, but infections do sometimes occur despite this prophylactic approach.
In 2019, the FDA issued a warning that use of absorbable mesh patches to help the heart's left ventricle contract more efficiently could be linked to an increased rate of infection, prompting a number of research groups to study this association in more detail. Now, researchers at the University of California, San Diego have shed new light on the issue, by describing genetic differences that may predict whether a patient is more likely to become infected.
"It is generally assumed that all staph are bad, but we believe there are different types of staph, and some of them are more likely to be trouble than others," said Victor Nizet, a Howard Hughes Medical Institute investigator who directs the Skaggs School of Pharmacy's Center for Immunity, Infection and Inflammation at UC San Diego.
In experiments using tissue culture models that mimic the heart valve and left ventricular assist device settings, Nizet and his team found that staph isolates from infected patients had distinct mutations and gene expression patterns that enabled them to better adhere to both mesh material and the surface of the blood-contacting device.
In patients who had cardiac device infections and S. aureus, 86% tested positive for mutations in a specific gene, lukF-PV. In mice experiments, the deletion of this gene from S. aureus reduced infections in mice that were implanted with the materials.
The researchers note that lukF-PV mutations in the S. aureus genome can be quickly and cost-effectively identified by PCR assay.
"We believe this represents the first example of how genetic features of a patient's infecting bacteria could predict infection risk and potentially be targeted for prevention or treatment," Nizet said.
The team believe that their findings can be quickly turned into clinical diagnostic tools to identify high-risk patients for device-based infection and that targeted therapies will follow soon after.
The study, "S. aureus lukF-PV mutations enhance adhesion and infection of left ventricular assist device materials," was published in the journal Nature Communications on Jan. 18.
