[Value of the technique of cellular lysis by thermic shock in the isolation of bacteria causing osteoarticular infections].

Abstract

The purpose of this work is to compare, a conventional technique, for bacterial isolation, with a lysis-centrifugation method using a rapid freezing in liquid nitrogen, followed by decongelation at 37 degrees C for bone and joint samples. The bone and joint specimens were biopsies and punctions (35 cases) or fistula (10 cases). The residual antibiotic activity of the sample was determined using a susceptible strain of Micrococcus luteus and of Staphylococcus epidermidis. Among the 45 samples, 20 were sterile with both methods among which 8 exhibited a residual antibiotic activity which may have contributed to isolation failure. In 12 cases, bacterial isolates were obtained with both methods. Cultures were obtained from 13 samples with the lysis centrifugation method alone. The isolates were 4 Staphylococcus aureus, 8 coagulase-negative Staphylococcus and 1 Acinetobacter sp. These results suggest that the intracellular location of bacteria may be responsible for the negative cultures from bone or joint specimens.