Catheters with and without AcryMed’s
SilvaGard treatment

Infection control is at its very best when it prevents infection from occurring. Hospital-acquired infections (HAIs) have drawn much national attention in the past few years, and the search for means and ways to thwart HAIs has stepped up. Consequently, antimicrobials are getting increased attention as a result, because they can be useful in both preventing and treating infection. Manufacturers are working hard to find new uses for antimicrobials and novel ways to incorporate them into patient-care products.

Turning silver into gold
Silver is being highlighted due to its inherent antimicrobial property. Before you pile on the jewelry, you ought to know that, to be deadly to microbes, it must be ionic silver, the form that is dissolved in fluid, not the metallic form, explained Jack McMaken, president, AcryMed, Portland, OR. "Silver as an antimicrobial has been around for hundreds of years, but only in the past 10 years has it been more accepted as a broad-spectrum antimicrobial and incorporated into wound-care products," said McMaken. A few serendipitous aspects of using ionic silver as an antimicrobial is that it’s virtually impossible for relevant bacteria to develop resistance to it, it doesn’t damage healthy tissue, it promotes faster healing by reducing bioburden, and it has persistence that can last up to 8 days, depending on conditions. The trade-off is that "the cost difference is 25% to 50% higher than hydrogels, foams, or hydrocolloids," stated McMaken, "but silver gives more bang for the buck because dressing changes are needed less frequently, which reduces product and nursing costs, and wound healing is improved, reducing the risk of systemic infection and associated costs."

McMaken explained how silver works when applied to wound dressings: "Ionic silver is activated by wound exudate." (Exudate is a $2 word scientists use for that icky stuff that oozes from a wound.) "Bacteria have a desire to capture silver; the silver ions kill the bacteria by attacking up to 10 different sites of the bacterial cell, preventing bacterial reproduction. Bacteria replicate every few hours and can mutate to develop antibiotic resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA). Because ionic silver acts in many different ways against the bacteria, it’s virtually impossible for bacteria to develop resistance to it. Bacteria give off toxins that impede the rate of healing, so another valuable plus of ionic silver is that, by reducing bioburden in the wound, it promotes faster healing."

As the exclusive distributor, Medline IndustriesInc., Mundelein, IL, markets AcryMed’s SilvaSorb products. Jonathan Primer, president, Dermal Management System Division, added: "Silver helps prevent use of antibiotics because it reduces bacteria on the skin, which reduces the risk of infection developing. It facilitates wound healing regardless of the setting, of wound depth, and whether it’s draining or not. It takes only one part per billion for ionic silver to be antimicrobial and kill bacteria. Controlled-release ionic silver products like SilvaSorb release silver at between one and two parts per million, releasing antimicrobial power well below the level that would damage healthy skin.

In addition to wound dressings, Primer also noted that "ionic silver has been built into a cuff that goes over the insertion site of a catheter, where chance of infection is significant, to keep bacteria from migrating." A huge bonus is that, "whereas the widely used chlorhexidine gluconate (CHG) is contraindicated for use in children, ionic silver is safe for children, and data show the activity of silver is just as good as CHG."

Primer also pointed out that this particular cuff silver dressing is more comfortable for the patient and presents less chance of an adverse reaction. "It’s a preventive treatment, so infection never gets a foothold in the first place, meaning antibiotics aren’t needed." No need for antibiotics means antibiotic resistance isn’t a threat.

Medline also applies antimicrobials to fabrics with their HaloShield textiles line. Charlie Coe, director of HaloShield Textiles, describes HaloShield as "Velcro for chlorine. HaloShield grabs the chlorine molecules in normal laundering and anchors them to the textile. Bacteria can’t flourish because the chlorine kills 99.9% of the bacteria in minutes. The effect lasts the lifetime of the fabric; in fact the fabric would break down before the HaloShield would."

 In August 2004, Medline released HaloShield bed linens, impregnated with stabilized chlorine-based sanitizers that kill pathogens including MRSA and vancomycin-resistant Enterococcus. Coe told Healthcare Purchasing News that the increased cost for HaloShield-treated linens is minimal: "For a 150-bed facility, it costs only 5 cents more per bed per day on average, only pennies per day in return for added protection for patients, staff, and visitors. The CDC says preventing one nosocomial infection can save $14,000 on average." Medline intends to apply HaloShield to other textiles such as laboratory coats (introduced this month) and cubicle (privacy) curtains in the near future.

First Water from across the
Big Water
Another interesting answer to antimicrobial wound dressings is coming out of England. First Water, a British company soon expanding to the United States through partnerships, makes wound dressings containing no added antimicrobials. Their polymer gel and foam work to kill bacteria on contact by "creating a high osmotic stress, causing microorganisms to lose vital water and die," said Peter Walker, head of sales and marketing, Ramsbury, UK. Walker maintains that the gels retain their antimicrobial properties for more than 21 days, "far longer than the normal time frame for a wound-dressing application, which normally is 3 to 5 days, depending on the level of exudate." The microbial kill rate is impressive, too, said Walker. When challenged with Pseudomonas aeruginosa, S aureus, and Escherichia coli, "the colony counts in all cases had reduced from several million to less than 5, between 24 and 72 hours, and this was maintained for over 28 days."

Walker listed the advantages of First Water foam and gel wound dressings: "They’re suitable for treating wounds across the entire wound-healing continuum from necrotic wounds, where the dressing is able to donate large quantities of fluid, to highly exuding leg ulcers, where it is able to absorb significant quantities of exudates; the dressing provides a cooling, soothing environment, making it suitable for treating first- and second-degree burns, with the suitability for third-degree burns currently being evaluated; the nature of the dressing seems to reduce the pain felt by a patient throughout the dressing application; it promotes healing; it is able to absorb more exudate from a wound than conventional foam and hydrocolloid dressings; the rate of absorption is higher than a hydrocolloid; it is breathable; it controls moisture to stop the wound from becoming macerated; it is non-adherent to the wound bed and so does not cause trauma to the wound when the dressing is changed; it is clear or blue so the wound can be monitored; it absorbs slough, and it adsorbs and kills bacteria. In summary, he concluded, "it manages pain, manages microorganisms, and manages the wound." As for cost, Walker notes that "considering the features the dressings offer, we aim to be competitive in the market."

Beating biofilm
Biofilm can present a problem in certain clinical environments such as wounds, pressure ulcers, medical devices, and indwelling catheters. Planktonic bacteria are normally found floating on the skin, but in a biofilm, bacteria have attached themselves to damaged tissue or perhaps a medical device, have clumped together in multiple layers, and are encapsulated by a sugar-based coating secreted by the bacteria, explained Lawton Seal, PhD, senior program manager, research and development, Surgical Division, HEALTHPOINT Ltd, Fort Worth, TX. "These bacteria are 500 to 1,500 times harder to kill than normal bacteria, because the coating makes them harder to reach and penetrate."

First Water’s hydrogel wound dressing

Because biofilm is protected, it provides a nidus for continuing infection, so antimicrobial persistence is important in thwarting the growth of biofilm. Steve Owens, marketing director, pointed out that only alcohol-based products, not CHG or iodine alone, are really effective for quick kill. Topical alcohol and iodine used alone are short-acting, whereas HEALTHPOINT’s Actiprep employs alcohol preserved with zinc pyrithione for quick kill accompanied by persistence lasting 3 days or more. This persistent, preventive killing power is referred to as "cumulative effect," said Owens. "In 15 seconds, 50% of the bacteria are killed; within 2 minutes, virtually all of the bacteria are killed. ACTIPREP acts against both biofilm and planktonic forms of bacteria." Quick kill and persistence work together to prevent rebound of skin colonization, which could prevent or reduce catheter-associated or surgical-site infections. An added attraction is that irritation and sensitization don’t present a problem, as can products that contain iodine or CHG.

Looking ahead
These are only a few of the innovative antimicrobial products sweeping into the field of infection control. As the battle against HAIs continues to gather momentum, keep your eyes open for new and better products, because the search is on for antimicrobial products that don’t contribute to the danger of antimicrobial resistance while promoting faster healing and keeping patients more comfortable.