[Microbiological pitfalls in the diagnostic of bone and joint infections].
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Biomedical subjects
Publications and source records attributed to N Desplaces.
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Peroperative contamination is the most frequent cause of infection after arthroplasty. For other cases of infection subsequent to bacteremia or a neighboring focus, it would be more appropriate to use the term "secondary" infections rather than hematogeneous infections. Arguments favoring secondary infection include long symptom-free interval between prosthesis implantation and the infectious episode, a causal germ not generally responsible for peroperative infection, presence of a distant infectious focus, positive blood culture, and a positive bacteriological sample from the prosthesis level showing the same strain as grown from the distant focus or blood samples. Both acute and chronic infections are observed, leading to prosthesis dysfunction. History taking generally identifies a neglected acute but transient episode. Search for a bacteriological diagnosis must be completed before initiating an antibiotic regimen. If detected very early, washing with open synovectomy and resection of suspicious tissue should be attempted in order to maintain the implant if possible. Local antibiotics have proven efficacy. Beyond a certain delay, treatment for chronic infection usually requires removing the prosthesis, cleaning the bone interface, and new arthroplasty delayed or not. Search for the portal must be undertaken early in order to initiate appropriate local treatment. The causal event may be any invasive procedure, with or without material implantation. The risk-benefit ratio for antibiotic prophylaxis remains to be determined.
BACKGROUND: Mycobacterium xenopi spinal infections were diagnosed in 1993 in patients who had undergone surgical microdiscectomy for disc hernia, by nucleotomy or microsurgery, in a private hospital. Contaminated tap water, used for rinsing surgical devices after disinfection, was identified as the source of the outbreak. Several cases were recorded in the 4 years after implementation of effective control measures because of the long time between discectomy and case detection. The national health authorities decided to launch a retrospective investigation in patients who were exposed to M xenopi contamination in that hospital. METHODS: Mailing and media campaigns were undertaken concurrently to trace exposed patients for spinal infections. Patients were screened by magnetic resonance imaging (MRI), and the scans were reviewed by a radiologist who was unaware of the diagnosis. Suspected cases had discovertebral biopsy for histopathological and bacteriological examination. FINDINGS: Of 3244 exposed patients, 2971 (92%) were informed about the risk of infection and 2454 (76%) had MRI. Overall, 58 cases of M xenopi spinal infection were identified (overall cumulative frequency 1.8%), including 26 by the campaign (mean delay in detection 5.2 years, SD 2.4, range 1-10 years). Multivariate analysis showed that the risk of M xenopi spinal infection was related to nucleotomy and high number of patients per operating session. INTERPRETATION: Failures in hygiene practices could result in an uncontrolled outbreak of nosocomial infection. Patients who have been exposed to an iatrogenic infectious hazard should be screened promptly and receive effective information.
In a randomised double-blind trial conducted between 1990 and 1994, 616 patients from 43 centres, pefloxacin (group P, 316 patients) and a cefazolin-oxacillin combination (group C, 300 patients) were compared in the prophylaxis of bone infection after grade 1 and 2 open leg fractures. Samples were obtained at emergency, before and during surgery, and from drain aspirates. Antimicrobial susceptibility, slime production and adherence properties of the bacteria were tested. Cultures at emergency and before surgery showed similar distributions of gram-positive and gram-negative bacteria in both groups, while wound closure and infecting isolates showed prevailing gram-positive bacteria in group P and gram-negative bacteria in group C. Positive cultures at each stage were correlated with the occurrence of infection but were not predictive of the infecting species, which were nosocomial bacteria in most cases. Positive cultures at wound closure warn of a higher infection risk. Twenty-one of 316 (6.6%) patients in group P and 24 of 300 (8%) in group C were considered infected within 3 months. The difference is not significant (chi-square test = 0.42; P = 0.51). Infecting strains were isolated from 38 patients (group P, 18; group C, 20). Infecting species, although not predictable, appear to be those escaping the spectrum of the prescribed antimicrobial prophylaxis.
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We studied the SmaI and SstII macrorestriction patterns of 54 Staphylococcus epidermidis strains isolated from 14 patients infected following the implantation of joint prostheses. Multiple strains from pus and infected tissue specimens of each patient were selected on the basis of different colony morphologies and drug resistance patterns. The same criteria were used to select 23 S. epidermidis strains from hand swabs of eight healthy individuals. For 10 of the 14 patients, all the intrapatient strains appeared to be closely or possibly related, whereas related strains were detected in the skin flora of only one of the eight healthy individuals. This observation suggests that, in most cases, the patients were infected by a single S. epidermidis clone which subsequently underwent rearrangements that yielded derivatives with divergent phenotypes and, occasionally, divergent macrorestriction patterns. The four patients whose specimens contained unrelated S. epidermidis strains were probably infected with several polyclonal strains.
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THE PURPOSE OF THE STUDY: Was to compare the efficacy of a single 800 mg injection of Pefloxacin (PF) versus 2 days of cefazolin (1 gr.Q.6 H) followed by 3 days of oxacillin (1 gr.Q.8 H) in patients with an open tibial fracture and to examine the predictive factors for infection. A double-blind double dummy, multicentric, randomized trial was performed. 616 adults with an open tibial fracture requiring single-stage bone coverage were included. The end point was wound infection within 3 months. RESULTS: Within 3 months, 21/316 patients were infected in the PF group (6.6 p. 100) versus 24/300 in the CZ-OX group (8 p. 100), the difference was not significant (95 p. 100 Cl for difference: -4.8 p. 100 to 2.1 p. 100). Twenty one strains were isolated in 18 infected patients in the PF group, and 27 in 20 patients in the CZ-OX group. Negative gram bacteria were less frequent in the PF group (10 p. 100) than in the CZ-OX group (48 p. 100), and positive gram bacteria were more frequent in the PF group (90 p. 100) than in the CZ-OX group (52 p. 100). Independent risk factors for infection were severe contamination, widespread contusion, unstable fracture, positive sample in the emergency room and at the end of surgery. Resistant infecting bacteria rate was 24 p. 100 in infected cases. CONCLUSION: There was no difference in infection rates after surgery for open tibial fractures between a 800 mg injection of Pefloxacin and 2 days of pephazolin followed by 3 days of oxacillin. Infecting bacteria were mainly nosocomially acquired.
Several atypical sucrose-negative Yersinia strains, isolated from clinical samples and sometimes associated with symptoms, proved to have full virulence potential in in vitro and in vivo testings. DNA-relatedness studies revealed that they were authentic Yersinia enterocolitica strains. Therefore, atypical sucrose-negative Yersinia isolates should be analyzed for their virulence potential.
We report a retrospective study of 14 Peptostreptococcus magnus bone and joint infections, following orthopaedic prostheses or implantation of fixation devices, diagnosed in two Paris hospitals between 1992 and 1996. Five patients experienced a knee joint infection after anterior cruciate ligament reconstruction with 4 artificial grafts, and 9 caught joint or wound infections, after limb traumatic injuries or bone neoplastic ruptures involving femur, tibia, calcaneum and humerus, treated by arthroplasty or osteosynthesis with implantation of biomaterials. Septic arthritis was experienced one week to one year after reconstructive surgery, and had evolved for several months to years before etiologic diagnosis in 5 cases. Specimens of pus, tissues or removed implants produced numerous slow growing small colonies of Gram positive cocci arranged in clumps on culture media incubated in anaerobic atmosphere only. In 10 patients, the same organism was disclosed in several separate specimens. The identification of P. magnus was assessed by the enzyme profile (rapid ID 32A API strips), gaz liquid chromatography, catalase and coagulase production, resistance to novobiocin and Na polyanethol sulphonate. Antibiotic sensitivity testing performed by disc method was constant to penicillin G, amoxicillin, cefuroxime, cefoxitin, imipenem and pristinamycin with penicillin G MICs < 0.125 mg/l and metronidazole MICs < 1 mg/l. Erythromycin, clindamycin, rifampicin, tetracycline and fosfomycin were active against more than 70% of P. magnus. All patients were cured after a prolonged course of various antibiotics and surgical removal of the foreign material whenever possible. We studied in vitro binding of P. magnus with extracellular matrix proteins adsorbed onto biomaterials, by particle agglutination assays of latex beads coated with proteins. Eighty one% of strains bound to collagen, 69% to fibrinogen and 46% to fibronectin. Comparison of orthopaedic strains with strains of other infections and from skin showed a correlation between P. magnus from bone and joint infections and their fibrinogen binding ability (69% against 20%, p < 0.05).
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Staphylococcus aureus BM4626 (ciprofloxacin MIC, 0.5 microgram/ml) and BM4627 (ciprofloxacin MIC, 32 microgram/ml) were isolated from the same patient before and during pefloxcin therapy for septic tibial nonunion, respectively. The two strains had similar serotypes and indistinguishable phage types and SmaI-generated restriction fragment length polymorphisms. Portions of the gyrA (codons 60 to 120) and the gyrB (codons 420 to 480) genes of each clinical isolate were amplified by PCR and sequenced. Strain BM4627 had a serine-to-leucine substitution resulting from a cytosine-to-thymidine mutation at codon 84 of gyrA relative to the sequence of the gyrA gene of BM4626. Norfloxacin accumulation, measured in a whole-cell uptake assay, was significantly lower in BM4627 than BM4626. These data indicate that double mutants can be selected in vivo under fluoroquinolone therapy.
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