PEPTOSTREPTOCOCCUS MAGNUS BONE AND JOINT INFECTIONS AFTER ORTHOPEDIC-SURGERY - 14 REPORTS, AND PATHOGENIC FACTORS

We report a retrospective study of 14 Peptostreptococcus magnus bone a nd 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 graftings, and 9 c aught joint or wound infections, after limb traumatic injuries or bone neoplastic ruptures involving femur, tibia, calcaneum and humerus, tr eated by arthroplasty or osteosynthesis with implantation of biomateri als. Septic arthritis was experienced one week to one year after recon structive surgery, and had evolved for several months to years before etiologic diagnosis in 5 cases. Specimens of pus, tissues or removed i mplants produced numerous slow growing small colonies of Gram positive cocci arranged in clumps on culture media incubated in anaerobic atmo sphere only. In 10 patients, the same organism was disclosed in severa l separate specimens. The identification of P. magnus was assessed by the enzym profile (rapid ID 32A API strips), gaz liquid chromatography , catalase and coagulase production, resistance to novobiocin and Na p olyanethol sulphonate, antibiotic sensitivity testing performed by dis c method was constant to penicillin G, amoxicillin, cefuroxime, cefoxi tin, imipenem and pristinamycin with penicillin G MICs < 0,125 mg/l an d metronidazole MICs < 1mg/l. Erythromycin, clindamycin, rifampicin, t etracycline and fosfomycin were active against more than 70 % of P. ma gnus.. All patients were cured after a prolonged course of various ant ibiotics and surgical removal of the foreign material whenever possibl e. 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. Eigty one % of strains bound to c ollagen, 69 % to fibrinogen and 46 % to fibonectin. Comparison of orth opaedic strains with strains of other infections and from skin showed a correlation between P. magnus from bone and joint infections and the ir fibrinogen binding ability (69 % against 20 %, p < 0,05).