髋关节置换术后感染的微生物特点及药敏分析

Analysis of microbiology and antibiotic susceptibility in 131 cases of prosthetic hip infections

目的对髋关节置换术后进行二期翻修的感染病例进行微生物学和药敏分析。方法选取自2007年1月1日至2013年12月31日解放军总医院骨关节科髋关节置换感染行二期翻修的患者进行回顾性研究，选取术中可疑组织做细菌培养，分析微生物种类、数量及抗生素药敏结果。结果本组患者共131例，术中培养阳性96例，阴性培养率为26．7％。所有感染病例中近50％病例原发病为骨折病例，31．3％的病例之前有过手术史。革兰阳性菌占74．3％，革兰阴性菌占20．2％，真菌占5．5％，混合感染比例为11．5％。凝固酶阴性葡萄球菌（CNS）是检出比例最高的菌株，达到38．53％，其次是金黄色葡萄球菌，占19．3％。耐甲氧西林葡萄球菌（MRS）的检出比例较高，达到29．4％（32／109），占葡萄球菌属的44．4％。革兰阴性菌主要以铜绿假单胞菌和大肠埃希菌为主。真菌感染主要以白色念珠菌为主。混合感染中最常见的菌株是肠球菌。抗生素药敏情况提示：指南推荐的头孢唑啉和头孢呋辛对CNS和MRS耐药情况严重，普通的第三代，第四代头孢对格兰阴性菌耐药较严重。对革兰阳性菌敏感率高的药物有万古霉素，利奈唑胺，利福平，对革兰阴性菌敏感率高的药物有阿米卡星，哌拉西林／他唑巴坦，头孢哌酮／舒巴坦，左氧氟沙星，碳青霉烯类。结论关节置换术后感染的细菌主要由凝固酶阴性葡萄球菌引起，耐甲氧西林葡萄球菌比例较高，经验型用药可以选用万古霉素来覆盖革兰阳性菌，左氧氟沙星，哌拉西林／他唑巴坦（头胞哌酮／舒巴坦）或碳青霉烯类药物来覆盖阴性菌。应当根据药敏结果及时调整抗生素。

Objective To explore the microbiological etiology of prosthetic hip infections during two-staged revision and analyze antibiotic susceptibility of bacteria isolated from infected hip arthroplasty specimens so as to provide clinical recommendations for empiric prophylactic and therapeutic antibiotics therapy. Methods A retrospective review was conducted for hospitalized patients of prothetic hip infections during two-staged revision between January 1, 2007 and December 31, 2013. Suspicious intraoperative tissues were cultured and microbiological data sets and antibiotic susceptibility of bacteria were analyzed. Results A total of 131 patients met the inclusion criteria. Micro-organisms were isolated in 96 patients. The negative culture rate was 26. 7%. Nearly half of primary diseases were of fractures and 31.29% of all infected patients had previous surgery. Gram-positive isolates were the most common genus encountered （n =81, 74. 3% ） , followed by Gram-negative isolates （ n = 22, 20. 2% ） and fungal isolates （ n = 6, 5.5% ）. Polymicrobial infections accounted for 11.5%. Coagulase-negative staphylococci was the most common causative organism of infection （ n = 42, 38.5% ） , followed by Staphylococcus aureus （ 19. 3% ）. The proportion of isolated methieillin-resistant Staphylococcus was 29.36% for all organisms and 44.4% for Staphylococcus. Gram-negative isolates were dominated by Pseudomonas aeruginosa and Escherichia coll. Fungal isolates were dominated by Candida albicans. Enterococcus was the most common causative organism of polymicrobialinfection. The results of antibiotic susceptibility showed cefazolin and cefuroxime were poorly susceptible to coagulase negative staphylococci （CNS） and methicillin-resistant staphylococcus （MRS）. Some third and fourth-generation cephalosporins also had problems of bacterial resistance to Gram-negative isolates. Some antibiotics such as vancomycin, linezolid and rifampin were sensitive to Gram-positive isolates. Some antibiotics such as amikacin piperacillin/tazobactam, cefoperazone/sulbactam, levofloxaeinareand carbapenems were sensitive to Gram-negative isolates. Conclusion Most infections are caused by staphylococci. The proportion of isolated methicillin-resistant Staphylococcus is high. Empiric antibiotics should include vancomycin for Gram-positive organisms and piperacillin/tazobactam （cefoperazone/sulbactam）, levofloxaeinare or carbapenems for most Gram-negative bacteria. Antibiotics should be timely adjusted according to the antibiotic susceptibility results.