Biofilm development is a major factor in the pathogenesis of implant-related infections. However, there are only a low number of studies that analyses the ability of clinical isolates of bacteria to develop biofilm in vitro. Here we study biofilm development in several strains of Staphylococcus aureus and Coagulase-negative Staphylococcus (CNS) consecutively isolated from retrieved orthopaedic implants from patients diagnosed of implant-related infections.

We have evaluated in vitro biofilm development using the crystal violet technique in microtiter plates. Biofilm development was confirmed by visual microscopy and Confocal Laser Scanning Microscopy. Staphylococcal strains were isolated from implant-related infections by sonication of retrieved prosthesis as previously published by our group, and identified using conventional methods.

Twenty-seven strains (15 S. aureus, nine S. epidermidis, and one each of S. hominis, S. lugdunensis and S. warneri) were included in the study. Four strains of S. aureus (26.7 %) and one strain of S. epidermidis (8.3 %) did not develop biofilm in the test, showing OD lectures almost identical to the negative control. No statistical differences were detected between the two groups. The microscopic examination confirms this finding. Among the biofilm-producing strains, an important difference of the amount of biofilm produced was detected. One strain (S. aureus) produced biofilm in greater amount than all other strains, detectable even by visual examination of the plate.

In conclusion, not all staphylococcal strains isolated from implant-related infections are able to develop biofilm in vitro. There must be other pathogenic factors that are important in the pathogenesis of implant-related infections and need to be studied in order to develop a better strategy for treat these infections.