A new antibacterial coating for intravascular catheters could one day help prevent bloodstream infections, the most common type of hospital-acquired infection.
“These kinds of infections are a major burden for hospitals, health care providers, and most of all for patients,” says Anita Shukla, an assistant professor of engineering at Brown University. “We wanted to develop a coating that could both kill planktonic [free-floating] bacteria and prevent colonization of bacteria on surfaces. The initial data that we gathered for this paper shows that we have something really promising.”
The researchers showed in lab tests that a polyurethane coating that can be readily applied to various medically relevant surfaces and that gradually releases a drug called auranofin, can kill methicillin-resistant Staphylococcus aureus (MRSA) bacteria for nearly a month. The tests also showed that the coating could prevent the formation of MRSA biofilms, which, once established, are especially resilient to antimicrobial treatment.
More than 150 million intravascular catheters are implanted each year in the United States alone, and 250,000 patients a year develop infections, 25 percent of which are fatal. Even when successfully treated, infections can add up to millions of dollars in extended hospital stays.
Previous approaches to the problem have had limited success, the researchers say. Other antibacterial coatings tend to lose their effectiveness after two weeks at most, often because they release their drug payload too quickly. Other coatings also tend to use traditional antibiotics, raising concerns about antibiotic resistance over long term use.
New job for an arthritis drug
For the new coating, Shukla and colleagues utilized auranofin, a drug the US Food and Drug Administration originally developed and approved to treat arthritis. Studies have shown that the drug is also highly effective in killing MRSA and other dangerous microbes. In addition, it works in ways that make it hard for bacteria to evolve a natural resistance. Researchers have never incorporated the drug into a coating technology.
To make the coating, the researchers dissolved polyurethane and concentrations of auranofin in a solution, which was then deposited onto a catheter. The solvent is then evaporated away, leaving a stretchable yet durable polymer coating. Mechanical testing showed that the coating can stretch up to 500 percent without breaking.
To test the coating’s effectiveness, the researchers placed coated catheters in MRSA both in solution and on agar plates where MRSA bacteria thrive. The experiments showed that the coatings were able to inhibit MRSA growth for up to 26 days, depending on the initial concentration of auranofin used in the coating.
Biofilm defense
The researchers also used bioluminescence imaging to look for signs of biofilm formation. Those experiments showed that the coatings prevent any trace of biofilm. For comparison, the researchers also tested a catheter loaded with a more traditional antibiotic, highly effective against free-floating MRSA, which was unable to prevent biofilm formation.
“The antibiofilm finding is very critical,” Shukla says. “Biofilms have really effective ways of evading antibiotics, which makes them thousands of times more difficult to treat in terms of the concentration of drug needed compared to planktonic bacteria. The fact that these coatings are able to prevent biofilms from forming in the first place is really important.”
Preliminary tests for toxicity in the lab showed that the coatings had no adverse effects on human blood or liver cells, but more testing is required before the coating is for use with patients, Shukla says. The fact that the FDA has approved both of the coating’s components for other uses should speed the approval process for in vivo testing.
“We’re hopeful that the initial results we show here will soon translate to the clinic,” Shukla says.
Additional researchers from Brown contributed to the research, which appears in Frontiers in Cellular and Infection Microbiology.
Source: Brown University
