Sometimes good ideas don't always work out the way we expected.
New data reported this week show that implanting sponges soaked with antibiotics into surgical wounds may not reduce the incidence of infections as intended and may, in fact, actually increase them. The findings represent a blow to the manufacturer's efforts to get the sponges approved for use in the United States.
Post-operative infections are a problem with all types of surgery, but are particularly troublesome with colorectal surgery because the bowels are loaded with bacteria. The reported incidence of such infections ranges from 8.2% to 26%, and most experts agree that a figure of 18% to 20% is typical for such procedures.
One effort to prevent such infections is a collagen sponge containing the antibiotic gentamicin, manufactured by Innocell Technologies of Gallowston, Ireland. When one to five such sponges are implanted at a surgical site, they produce a high local concentration of the drug without producing a high systemic concentration. The sponge itself biodegrades and disappears within days to weeks. The sponge was first approved in Germany in 1985 and is now marketed in 53 countries. More than 2 million of the sponges have been used to treat about a million patients.
A team headed by Dr. Elliott Bennett-Guerrero of Duke University studied 602 patients undergoing colorectal surgery, randomly assigning half to receive the sponge plus conventional systemic antibiotics and half to receive only the systemic drugs. The team reported Wednesday in the New England Journal of Medicine that 90 of 300 patients receiving the sponges (30%) developed an infection, compared with 63 of 302 patients (20.9%) receiving conventional care. Patients receiving the sponges were also more likey to visit an emergency room or doctor's office for wound-related symptoms (19.7% versus 11%) or to be hospitalized for a surgical-site infection (7% versus 4.3%).
The same team of researchers reported in August in the Journal of the American Medical Assn. on a similar trial in heart surgery, where infections are less common. That trial enrolled more than 1,500 patients and found no benefit for the sponges: 8.4% of those receiving sponges developed an infection compared to 8.7% of those receiving standard care.
Both studies were sponsored by Innocell as part of its phase 3 trials to get the sponges approved by the U.S. Food and Drug Administration. Such approval now seems highly unlikely, experts said.
The researchers seemed at a loss to explain the findings. Perhaps the most likely possibility is a different spectrum of germs abroad, with a higher prevalence of bacteria sensitive to gentamicin. Another possibility is differences in surgical procedures.