Medical Device Daily Executive Editor

GAITHERSBURG, Maryland — The 37th meeting of the FDA's General Hospital and Personal Use Devices Panel, held on Friday, examined the use of antimicrobials on personal protective equipment (PPE), and, as has been the case in trials for other classes of devices, the panel concluded that controls should be used in any clinical trials.

The items discussed included medical and surgical gloves, surgical masks and surgical respirators, and gowns for isolation and surgery. Of these, only the isolation gowns are Class I products, which need no premarket clearance from the agency. But the addition of an antimicrobial pushes it to a Class II device. The rest of these items are already in Class II.

Sheila Murphey, MD, the agency's branch chief for infection control devices, said that FDA "has not cleared any medical gloves, surgical masks or N95 respirators which incorporate antimicrobial agents," but that it had cleared two surgical gowns thus equipped in the late 1970s.

Murphey said that other devices approved for impregnation with antimicrobial agents "have generally been devices associated with device-related infections, such as intravascular catheters" and the like.

The agency believes, she said, that while personal protective equipment is typically worn for only short periods of time — and also typically is not seen as a vector for hospital-acquired (nosocomial) infections — such equipment could discourage sanitary practices in hospitals, and the routine exposure of pathogens might also breed resistance to antibiotics.

The Centers for Disease Control and Prevention (Atlanta) recently estimated that as many as 90,000 hospital deaths per year can be attributed to nosocomial infections, and it is pushing hospital workers to adhere to sanitary standards (Medical Device Daily, March 13).

The market for such devices outside of hospital use is potentially huge in an age that treats bioterrorism as a threat that is every bit as real as that of nuclear annihilation during the Cold War period.

But CDC just this past week issued a statement that in an infectious disease pandemic, masks and respirators are likely to be of less help than simply avoiding those who are ill (Medical Device Daily, May 7, 2007).

Wava Trusscott, PhD, VP of scientific affairs for Safe Life (San Diego), briefly discussed filtration masks, saying that most N95 masks will capture particles at .3 microns or larger, which will snare anthrax and tuberculosis spores as well as most industrial dust.

He said that any masks that employ an electrostatic charge to trap particles may filter more effectively at first but will lose efficacy as water droplets accumulate, possibly retaining viruses "which are still alive." Any such viruses can be reintroduced into the air after the droplets reach "a critical mass."

Over a period of hours, the effectiveness can drop to below 10%, a consideration in circumstances of extended use, he said.

Stephen Rothenburger, PhD, of Ethicon (Somerville, New Jersey), discussed some of his experience in product development, briefly outlining the company's development of antimicrobials in suture materials. He said that staphylococcus is a main driver of interest in this area and that the company's experience in animal trials demonstrated that "animal studies have a lot of variability."

"In vitro testing can be really convincing, but is not always relevant." he said, because of the differences between the animal tests and actual use. As for duration of antimicrobial effect, the consensus was that a period of weeks was not relevant for these kinds of infections.

Rothenburger said that "the question [of toxicity] does come up a lot," but that the tests Ethicon runs for the treated sutures suggest that "there is absolutely no difference in biocompatibility" in terms of tissue reaction. However, he said that Ethicon's studies for treated sutures in animals did not examine animals that are already ill.

Rothenburger cited three ongoing studies to evaluate the use of antimicrobials in ventricular shunts for cranial use, saying that one such study at the halfway point "found such a significant effect — I think it was on the order of an 18% reduction in infections — [that] they stopped" the control arm and started using the treated shunts on all the subjects.

While he said that it is difficult to establish a useable model to test for resistance in many uses, "we keep a very close eye on that question," and that recently published studies indicate that "the risk of additional resistance is pretty much nil."

The first question for the panel was which primary indications or claims might a manufacturer make for such a product.

The panel said that for all three types of devices, the three primary indications might be:

• reducing/preventing infections on both patient and caregiver;
• reducing colonization on both;
• uppressing bacteria/viruses on the device.

After substantial discussion with members of the audience with some experience in the area of testing, the panel chairman, William Jarvis, MD, acting director of the hospital infections program at CDC, said, "in general, we would recommend testing include both dry and wet states, a variety of clinically relevant organisms, includes controls, and includes a variety of timepoints," ranging from "pretty short to several hours."

FDA also asked about a "reasonable possibility that the presence of an antimicrobial agent" on PPE might lead the wearer to be less vigilant regarding infection control procedures or proper techniques.

Fluryanne Leach, the chief of infection control service at Walter Reed Army Medical Center (Washington), said, "I feel it's definitely a risk and I'm not sure how much labeling is going to change it" because once hospital personnel are familiar with a product, most of them "reach into the box and grab some gloves."

On the other hand, "many healthcare workers are becoming skeptical" of changes and that most are not interested "in becoming the one to find out that there are problems down the road," Leach said.

The panel concluded that such a possibility exists but that the matter of usage patterns is more properly the domain of the institutions that purchase PPE products.