Infectious prosthetic hip joint loosening: bacterial species involved in its aetiology and their antibiotic resistance profiles against antibiotics recommended for the therapy of implant-associated infections.

Reliable microbiological diagnosis along with surgery and prolonged antibiotic therapy are key elements in the management of prosthetic-joint infections (PJIs). The purpose of this study was to characterize antibiotic resistance profiles of bacteria involved in the aetiology of PJIs. A total of 33 bacterial isolates cultured from 31 patients undergoing exchange of total hip prostheses were analyzed. The diagnostic approach toward isolation of prosthesis- associated microorganisms included sonication of retrieved implants and conventional cultures of periprosthetic tissues and synovial fluid. The in vitro resistance profiles of bacterial isolates were determined in relation to antibiotics recommended for the therapy of PJIs using the disc diffusion method, E-tests(®) and broth microdilution system. Coagulase-negative staphylococci (CNS) were predominant microorganisms followed by Staphylococcus aureus, Enterobacter cloacae, Streptococcus mitis, and Propionibacterium acnes. Twenty out of 30 and 12 out of 30 staphylococcal isolates were methicillin- and multi-drug resistant, respectively. Only two isolates were rifampicinresistant. All staphylococci were susceptible to glycopeptides and linezolid. This paper stresses the pathogenic role of staphylococci in patients suffering from implant loosening and reports high methicillin- and multidrug-resistance rates in these bacteria. Hence, antimicrobial susceptibility tests of individual bacterial isolates must always be performed to guide selection of the optimal therapeutic option.

Characterization of Staphylococcus epidermidis and Staphyloccocus warneri small-colony variants associated with prosthetic-joint infections.

We determined the frequency of isolation of staphylococcal small-colony variants (SCVs) from 31 culture-positive patients undergoing revision of total hip prosthesis for aseptic loosening or presumed prosthetic-joint infection (PJI). We analysed auxotrophy of cultured SCVs, their antimicrobial susceptibility profiles and their biofilm-forming capacity. Eight SCV strains were cultivated from six (19 %) patients. All SCVs were coagulase-negative staphylococci (CNS) with Staphylococcus epidermidis as the predominant species; there was also one Staphylococcus warneri SCV. The SCVs were auxotrophic for haemin, with one strain additionally auxotrophic for menadione. We noted the presence of two phenotypically (differences concerning antimicrobial susceptibility) and genetically distinct SCV strains in one patient, as well as the growth of two genetically related SCVs that differed in terms of their morphology and the type of auxotrophy in another. Seven out of eight SCVs were resistant to meticillin and gentamicin. In addition, antibiotic sensitivity testing revealed three multidrug-resistant SCV-normal-morphology isolate pairs. One S. epidermidis SCV harboured icaADBC genes and was found to be a proficient biofilm producer. This paper highlights the involvement of CNS SCVs in the aetiology of PJIs, including what is believed to be the first report of a S. warneri SCV. These subpopulations must be actively sought in the routine diagnosis of implant-associated infections. Moreover, in view of the phenotypic and genetic diversity of some SCV pairs, particular attention should be paid to the investigation of all types of observed colony morphologies, and isolates should be subjected to antimicrobial susceptibility testing.

[Large diameter femoral heads in primary alumina/alumina and XSPE/alumina total hip arthroplasty. A follow-up study of 50 hips after average 40 months and review of literature]. / Pierwotna calkowita bezcementowa endoprotezoplastyka stawów biodrowych--ceramika/ceramika i ceramika/polietylen XSPE z uzyciem glów o duzej srednicy. Ocena 50 bioder po okresie srednio 40 miesiecy i przeglad pismiennictwa.

INTRODUCTION: The aim of the study was a preliminary report of the use of large diameter alumina femoral heads in total hip arthroplasty. MATERIAL AND METHODS: In the years 2005-2008 50 THRs were implanted in 48 patients with the use of 36 mm alumina femoral heads. 5 women and 43 men in the age from 35 to 75 years (average 61 years) were operated on. Primary osteoarthritis was the cause of 41 arthroplasties, and AVN of femoral head of 9 surgeries. 18 alumina/alumina and 32 polyethylene/alumina THRs were implanted. The prospective study consisted of clinical examination with Harris Hip Score and X-ray evaluation. AP and lateral view X-rays were evaluated. The incidence of radiolucent lines around acetabular cups were noted with DeLee and Charnley zones and around stems with Gruen's zones. RESULTS: The follow up is from 24 to 58 months (average 40 months). There was an increase in Harris Hip Score from average 37 points (from 25 to 49 points) before operation to average 94 points (from 90 to 100 points) after the surgery. The incidence of postoperative dislocation have not been noted. Long-term postoperative X-ray examination have showed proper geometry of endoprostheses without radiolucent lines. Neither visible wear of bearing surfaces nor breakage of alumina components have been noted. CONCLUSIONS: 1) The use of 36 mm femoral heads in total hip arthroplasty decrease the risk of postoperative dislocation. 2) Innovative biomaterials: alumina ceramics and cross-linked polyethylene give chance for decrease the incidence of osteolysis.