No abstract

PCR for detection of 16S rRNA in tissue specimens obtained from hip joints is not superior to routine bacteriologic culture techniques for detection of low-grade infections. However, these results demonstrate that the loosening of cups in THPs do not usually result from nonculturable periprosthetic infection, if the microbiological processing is adequate.

Local delivery of gentamicin is an accepted method of infection prophylaxis in the surgery of open fractures. However, the few reports of studies into the effect of locally applied gentamicin on osteoblasts used inadequate methods. In our study, we used the wellcharacterised C2C12 cell line with reproducible differentiation pathway into the osteoblast lineage. We investigated the viability, cell number, alkaline phosphatase activity, and the expression of osteogenic genes of C2C12 cells after exposure to gentamicin at concentrations of 12.5-800 μg/ml for 48 h. Exposure of C2C12 cells to gentamicin (12.5-800 mg/ml) for 48 h showed no significant changes in the cell number, but cell viability was decreased by one-third at the tested concentrations of 200-800 μg/ml. The alkaline phosphatase activity was significantly decreased by one-third to one-half at any tested concentration (12.5-800 μg/ml) of gentamicin.

Staphylococcus epidermidis and Staphylococcus aureus are the most common causes of medical device-associated infections, including septicemic loosenings of orthopedic implants. Frequently, the microbiological diagnosis of these infections remains ambiguous, since at least some staphylococci have the capacity to reduce their growth rate considerably. These strains exhibit a small-colony phenotype, and often they are not detectable by conventional microbiological techniques. Moreover, clinical isolates ofS. aureus and S. epidermidis adhere to polymer and metal surfaces by the generation of thick, multilayered biofilms consisting of bacteria and extracellular polysaccharides. This study reports improved detection and identification of S. aureusand S. epidermidis by an in situ hybridization method with fluorescence-labeled oligonucleotide probes specific for staphylococcal 16S rRNA. The technique has proven to be suitable for the in situ detection of staphylococci, which is illustrated by the identification of S. epidermidis in a connective tissue sample obtained from a patient with septicemic loosening of a hip arthroplasty. We also show that this technique allows the detection of intracellularly persisting bacteria, including small-colony variants of S. aureus, and the differentiation of S. epidermidisfrom other clinically relevant staphylococci even when they are embedded in biofilms. These results suggest that the 16S rRNA in situ hybridization technique could represent a powerful diagnostic tool for the detection and differentiation of many other fastidious microorganisms.