A silver-based surface modification for devices prevents the creation of biofilms.
Though the increase of antimicrobial-resistant bacteria may pose an imminent threat, it is too soon to raise the white flag of surrender. Several developments in curbing infections contracted while in the hospital have been announced. They are in the form of a coating and a surface treatment. And they may just prove to be worthy foes.
Antimicrobial resistance is an alarming problem in hospitals, since patients tend to be vulnerable and thus more susceptible to infection. According to the Centers for Disease Control and Prevention (CDC), close to 2 million patients each year in the United States acquire an infection while in the hospital. Seventy percent of the bacteria that cause these infections are resistant to at least one of the drugs most commonly used to treat them. The most prevalent antimicrobial-resistant strains of bacteria are vancomycin-resistant Enterococcus and methicillin-resistant Staphylococcus aureus.
Many hospital-acquired, or nosocomial, antimicrobial-resistant infections can be attributed to the formation of biofilms on implanted medical devices. Biofilms occur when organisms secrete a sticky substance that enables the organism to adhere to a surface. The biofilms then synthesize a polysaccharide that envelops the organism, protecting it from the body’s defense system. AcryMed Inc. (Portland, OR; www.acrymed.com) has introduced a surface treatment that blocks this bacterial formation.
A microbiocidal coating for gauze kills bacteria and prevents it from recolonizing at wound sites.
SilvaGard is a silver nanoparticle technology that can be applied to devices without changing their composition. Though silver is recognized as an effective antimicrobial, it formerly was underused in the prevention of biofilms because of limited application methods, according to the company. Silver application as a form of surface modification has had drawbacks in the past. Conventional methods of application, such as sputter coating, can be expensive and coatings apply in a directional fashion from the source of the silver, reports Bruce Gibbins, PhD, founder and chief technology officer of AcryMed. Unlike other methods of silver application, SilvaGard is applied via a fluid-phase method. This procedure entails forming the silver in water so that the silver follows the water throughout all the crevice of a device that is suspended in the fluid bath. This treatment results in the thorough application of the coating in nooks and crannies that may be missed using other methods.
A number of tests conducted by AcryMed on the efficacy of silver concluded that the majority of devices treated with SilvaGard demonstrated a 99% reduction in bacterial growth, as compared with untreated devices. The company touts additional test results revealing that the product exhibited a complete resistance to biofilm formation. “We think that there’s a high degree of interest in making medical devices less susceptible to nosocomial infections,” says Gibbins. “Making medical devices more resistant to infection is important. I think that SilvaGard is a technology that will play a part in that.”
Materials successfully treated with the product include stainless steel, PEEK, polyurethane, silicone, and Teflon. It is suited for use on devices such as catheters, bone pins, and pacemakers. Catheters and other invasive devices are the leading cause of exogenous nosocomial infections because of their support of the development of biofilms. AcryMed also produces a line of ionic silver–based antimicrobial dressings and gel for wound care.
Whereas AcryMed has developed a surface solution that prevents the formation of biofilms, the University of Florida (Gainesville, FL; www.ufl.edu) and Quickmed Technologies Inc. (Gainesville, FL; www.quickmedtech.com) have announced a microbiocidal coating for wound dressings that kills the two most common antibiotic-resistant bacteria. The coating acts as a barrier, impeding bacteria from reaching the wound and recolonizing.
The distinguishable trait of this coating lies in the method of bacterial attack. Commonly used metals such as silver, iodine, and copper attack bacteria by traveling into the cell and reacting with essential proteins. Conversely, the coating developed by the University of Florida uses polyquats that interact with the negatively charged surface of bacteria, thus creating regions of membrane instability. The polymer essentially punches holes in the bacterial membrane, causing materials such as potassium, proteins, and DNA to leach out. The interaction of the polymer with the bacterial membrane is similar to sticking a pin in a balloon, according to Gregory Schultz, PhD, director of the University of Florida’s Institute for Wound Research and codeveloper of the coating.
According to the researchers, the coating will prove more effective than other antimicrobial methods, including silver-based dressings. Schultz predicts that since silver kills bacteria in the same manner as antimicrobials such as penicillin, bacteria will eventually develop resistance to silver as well. Because of the polymer’s method of killing bacteria by puncturing its membrane, it is virtually impossible for bacteria to develop a resistance to it, according to Schultz.
As a preventative measure to stave off infection, the coating can be chemically bonded to gauze bandages. Though the developers plan to expand the use of coating on wound dressings, they are currently collaborating with companies to apply the coating to cotton-based products such as ready-to-wear hospital clothing and bed sheets. The coating-protected clothing and sheets could prove to be invaluable in hospitals, since the transfer of bacteria from doctors to patients is among the leading causes of nosocomial infections. “The coating has the potential to significantly reduce the risk of transference of resistant bacteria within healthcare facilities,” says Schultz. A modified version of the polymer coating as a hand disinfectant for hospital use is also currently in development.
Though these advancements have been made in the fight against antimicrobial-resistant infection, a significant threat to patients remains. As Bruce Gibbins of AcryMed notes, “There’s pretty significant costs in both lives and in healthcare when overcoming infections.” An estimated 90,000 people die each year from nosocomial infections, according to the CDC. In addition to the increased patient risk, these infections also incur large price tags for hospitals. Substantial costs for treatment of hospital-acquired infections are a byproduct of prolonged patient stays and added drug treatments. In 2000, the World Health Organization estimated U.S. costs for treating nosocomial infections at a hefty $10 billion each year. Innovative biocidal products such as AcryMed’s SilvaGard and the University of Florida’s coating may significantly impact the medical community; however, many experts feel that maybe the war has only just begun.