Influence of Type of Screw on the Bacterial Adherence and Infection

Lee, Eun Woo; Kang, Ki Ser; Kang, Soo Yong; Jin, Whui Jae; Jeong, Sang In

Abstract

The purpose of the study was to evaluate the effect of commonly used orthopaedic material, stainless steel (SS) screw (2.7xlOmm, Synthes) and titanium (Ti) screw (2.7x10mm, Synthes), on bacterial adherence and infection. The bacteria used for this study was Staphylococcus epidermidis for its ability of adherence. For in vitro assay, screws of each material were placed into test tube containing 107 colony forming unit (CFU) of S. epidermidis in trypticase soy broth for 18 hours. Following incubation, each screws were treated either with trypsin or with an ultrasonic cleaner. For in vivo assay, we inoculated 5x107 CFU of S. epidermidis into the proximal tibial metaphysis of the rabbits, and then inserted Ti screw on the right side and SS screw on the left side. The amount of in vitro adherence of S. epidermidis was greater for SS screw than for Ti screw. Especially following trypsin treatment, SS groups yielded significantly higher bacterial counts than Ti group, respectively (1.4x105 CFU vs 2.8x104 CFU, p<0.05). We found a significantly higher bacterial count after use of SS screw than after Ti screw in rabbits in vivo assay also. Trypsin treatment for identifying biofilm embedded bacteria from implanted metal may be useful in the diagnosis of infection. Ti screw appears to have biocompatibility to inhibit bacterial adherence compared with SS screw in the rabbit tibial model.