Sensitivity and negative predictive value of swab cultures in musculoskeletal allograft procurement

Seventy-five fibular specimens were obtained from postmortem donors using aseptic surgical techniques. All specimens were swabbed following the same technique as routinely used for retrieved musculoskeletal grafts. After swabbing, the specimens were placed in BHI-culture medium. Three different protocols were subsequently followed: (1) culture of the entire bone specimen in BHI-culture medium, (2) culture of the swab incubated on blood agar and chocolate plates, and (3) culture of the swab in BHI-culture medium. A control group included 20 sterilized bone specimens that were cultured entirely in BHI-culture medium according to Protocol 1. The sensitivity and negative predictive value were found to be 10% and 9% in Protocol 2 and 13% in Protocol 3. These findings imply that swab cultures are inadequate to detect bacterial contamination of musculoskeletal allografts in all cases. However, the instances of infection after transplantation of allografts bacteriologically screened according to Protocols 1 and 2 do not exceed those reported in other similar series. This suggests an acceptable bioburden.