膝关节置换术后感染的微生物学及药敏分析

Analyses of microbiology and antibiotic susceptibility in prosthetic knee infections

目的对膝关节置换术后感染进行二期翻修的病例进行微生物学和药敏分析。方法对自2007年1月1日至2014年2月28日解放军总医院骨关节科膝关节置换感染行二期翻修患者共78例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。结果本组术中培养阳性65例，阴性培养率为16．7％。在培养出的细菌中，75．7％为革兰氏阳性菌，20．5％为革兰阴性菌，真菌占2．7％，混合感染比例为15．4％。检出比例最高的菌株是凝固酶阴性葡萄球菌（46．6％），其次是金黄色葡萄球菌（20．5％）。耐甲氧西林葡萄球菌（MRS）的检出比例为34．3％（25／73），占葡萄球菌属的47．5％，比例较高。革兰阴性菌主要为大肠埃希菌（4／15）和鲍曼不动杆菌（4／15），其中所有的鲍曼不动杆菌均为混合感染。混合感染中最常见的菌株是凝固酶阴性葡萄球菌（12／25）和鲍曼不动杆菌（4／25）。药敏结果提示，头孢唑啉和头孢呋辛等指南推荐的抗生素耐药情况严重，耐药率分别达到43．5％和53．6％，普通的第三代，第四代头孢也有一定耐药性。敏感率高的药物有万古霉素，利奈唑胺，亚胺培南，利福平，头孢哌酮／舒巴坦，左氧氟沙星等。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。经验性预防性用药可选用万古霉素和头胞哌酮／舒巴坦来覆盖革兰阳性菌和阴性菌，治疗性用药可选用万古霉素和头胞哌酮／舒巴坦或碳青霉烯类药物。在药敏结果出来以后应根据药敏结果及时调整抗生素。

Objective To explore the microbiological etiology of prosthetic knee infections during two-staged revision and analyze antibiotic susceptibility of bacteria so as to provide clinical recommendations for empiric antibiotic therapy. Methods A retrospective review was performed for 78 hospitalized patients for prothetic knee infections undergoing two-staged revision between January 1, 2007 and February 28, 2014. Suspicious intra-operative tissues were collected and cultured. Microbiological data sets and antibiotic susceptibility of bacteria were analyzed. Results Micro-organisms were isolated from 65 patients. The negative culture rate was 16. 7%. The most common genus encountered was Gram-positive isolates （75.7%）, followed by Gram-negative isolates （ 20. 5%） and fungi isolates （ 2. 7%）. Polymicrobialinfections accounted for 15.4% of patients. The most common causative organism of infection was coagulase-negative staphylococci （46. 6% ） and followed by Staphylococcus aureus （20. 5% ）. The detection rate of methicillin-resistant staphylococcus （MRS） was 34. 3 % （25/73） and it accounted for 47.5 % of staphylococcus. Gram-negative isolates were dominated by Escherichia coli （ 4/15 ） and Acinetobacter baumannii （ 4/15 ）. All A. baumanniiscame from polymicrobial infection. Coagulase-negative staphylococci and A. banmannii were the most common causative organisms of polymicrobial infection. The results of antibiotic susceptibility showed cefazolin and cefuroxime were poorly susceptible to isolates. The drug resistance rates were 43.5% and 53.6%. Some third or fourth generation cephalosporins also have problems of bacterial resistance. Some antibiotics such as vancomycin, linezolid, imipenem, rifampin, cefoperazone! sulbactam and levofloxacin had high rates of drug sensitivity. Conclusion Most infections are caused by staphylococci. The proportion of isolated MRS is high. Empiric prophylacticantibiotics therapy may include vancomycin and cefoperazone/sulbactam to cover Gram-positive and Gram-negative organisms. Empiric therapeutic antibiotics therapy includes vancomycin and carbapenems. After the results of antibiotic susceptibility, antibiotics should be timely adjusted.