Antimicrobial peptides may prevent cement colonization, indicating they could be useful in preventing bacterial growth and subsequent biofilm formation, according to investigators from the United Kingdom.

As Staphylococcus epidermidis is a major cause of biofilm infections associated with indwelling medical devices and most prosthetic joint infections (PJI), increasing resistances among these isolates means new therapies are needed to prevent the initial adhesion of bacteria to biomaterial surfaces, study investigator Mathew Upton, PhD, said during his presentation at the 2010 Meeting of the Combined Orthopaedic Associations.

“[S. epidermidis] has only recently been recognized as a real cause of significant infection,” Upton said.

“It is now widely recognized that more than 80% of infections — and certainly the majority of those involving medical devices — have a biofilm element to their development,” he added, noting that his group was approaching the issue “from a different angle.”

This new angle, Upton reported, involves the incorporation of antimicrobial peptides directly into medical devices and materials to prevent the development of potentially dangerous biofilm.

Incorporating the peptides

His group incorporated lantibiotic gallidermin and NI01 with respective inhibitory activities of more than 5120 AU/mL and 2560 AU/mL into polymethylmethacrylate (PMMA) bone cement. Columns of bone cement with a diameter of 4 mm and a height of 7 mm were attached to the lid of a microtitre plate, then incubated with clinical biofilm forming S. epidermidis strain 156 for 1 hour.

These columns were then rinsed in phosphate-buffered saline (PBS) and immersed in PBS containing 0.25% glucose, ammonium sulfate and 1% tryptic soy broth. The growth of adhered bacteria was then monitored in real time using a kinetic plate reader for more than 48 hours, producing a time proliferation curve.

Further investigation is necessary

The investigators found that gallidermin and NI01, when incorporated into columns of PMMA cement, resulted in a significant decrease in the growth of clinical S. epidermidis isolate 156. This included a significant reduction in the growth of PJI-associated strains during the course of 96 hours.

According to Upton, the use of peptides could represent “a potential novel therapy” for preventing bacterial growth, and the incorporation of these materials into clinical use should be investigated.

“We are very interested in incorporating these into a number of areas, to be used in things like prosthetic joint infections,” Upton said. — by Robert Press

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