The Clinical Study Of Prosthetic Joint Infection Caused By The Non-tuberculosisgram-positive Bacillus

Objective: To review the patients with a prosthetic joint infection due togram-positive bacillus and analyze their clinical symptoms, laboratory andpathological examination outcomes, risk factors, treatment methods and results tosummarize the experience in diagnosing and treating this infection.Methods: Firstly, we retrospectively analyzed8cases who were suspected to beinfected by the gram-positive bacillus after joint replacement from August2007toSeptember2011and collected the patients’ following information:(1) age, gender,body mass index;(2) The diagnosis for primary total hip or knee replacement, thelifetime of the prosthesis, the type of infection;(3) body temperature, the localmanifestations of joint and the presence around the prosthesis during operation andthe X-ray reports;(4) Laboratory tests: erythrocyte sedimentation rate (ESR),c-reactive protein (CRP);(5)The results of pathological examination;(6) Themicrobiological findings from the aspiration and tissues culture. And then, thestandard for diagnosis of gram-positive bacillus prosthetic joint infection was adoptedto identify the infection or contamination. Secondly,24cases were randomly selectedfrom72cases who were infected by coagulase-negative staphylococcus as the controlgroup and the identified cases were considered as experimental group; after that, wecompared the clinical manifestations and risk factors between these two groups toexplore the characteristic of the prosthetic joint infection caused by gram-positivebacillus. Finally, the pathological examinations，laboratory tests results and the Harris（HSS）-score were compared between postinfection and reimplantation to assess thestrategies and results of the treatment.Results:6cases were identified as infection and the rest was considered ascontamination. The infection caused by the gram-positive bacillus has no difference with the infection caused by the coagulase-negative staphylococcus in the8common-seen risk factors and clinical manifestations (p>0.05) except bodytemperature (p<0.05). The bacteria cultured from the aspiration and intraoperativetissues were sensitive to the amikacin and ciprofloxacin and the diameter ofbacteriostatic ring were bigger than20mm. The average follow-up time of the6identified cases was43months and the average Harris-scores increased from41.6preoperatively to91.2postoperatively and the HSS-scores from32to83.Conclusions: The gram-positive bacillus is an infrequent cause of prosthetic jointinfection, but some cases were false-positive and this ratio is small. The infectioncaused by the gram-positive bacillus had no statistical difference with infectioncaused by the coagulase-negative staphylococcus in the8common-seen risk factors,the clinical manifestations except the body temperature. The sensitivity of thegram-positive bacillus to the amikacin and ciprofloxacin was still satisfying at present.The two-stage protocol and6weeks of antibiotic therapy of combination ofvancomycin and levofloxacin after removal of the prosthesis is the advisabletreatment for the most of the prosthetic infection caused by gram-positive bacillus; butit is difficult to cure the rare prosthetic infection caused by Mycobacterium chelonaein the same way, which is one of the gram-positive bacillus and resistant to manyantibiotics. To deal with this, removal of the prosthesis and elongation of theantibiotic therapy time must be needed. During the therapy, the accurate time forreimplantation can be indicated by ESR, CRP and the results of the intraoperativefrozen sections.