Antimicrobial Effect of Silver-Coated External Fixator Pins

Evaluation of a silver-impregnated coating to inhibit colonization of orthopaedic implants by biofilm forming methicillin-resistant Staphylococcus pseudintermedius

OBJECTIVES

To evaluate the in vitro antibacterial activity of a silver-impregnated coating against a biofilm-forming strain of methicillin-resistant Staphylococcus pseudintermedius (MRSP).

METHODS

A clinical MRSP isolate sourced from a failed canine knee implant was evaluated for biofilm production and used in the present study. Using a standard test method and a clinically approved titanium substrate, the antimicrobial activity of a novel silver plasma coating was determined at two times: five minutes after inoculation of the specimens (T0) and after 24 hours of incubation (T24). Scanning electron microscopy was used to evaluate the biofilm formation on specimens.

RESULTS

The tested clinical MRSP isolate was classified as a strong biofilm producer. The silver coating significantly reduced the MRSP growth more than four log steps compared to the non-coated specimens and showed more than 99.98% reduction in the number of colony forming units after 24 hours. Scanning electron microscopy images revealed that silver-coated surfaces did not manifest detectable biofilm, while biofilm formation was readily observed on the control specimens.

CLINICAL SIGNIFICANCE

The silver coating exhibited excellent activity against the multidrug resistant biofilm-forming MRSP isolate. The next stage of this work will involve testing in an animal model of orthopaedic infection. Positive results from animal studies would support the introduction of the silver plasma coating as a new strategy for preventing implant contamination, biofilm formation, and surgical infection in dogs undergoing orthopaedic surgery.