AAOS：多次细菌培养或可提高骨折内固定术后感染诊断率

引言：在骨不连或可能存在的深部内植物感染的情况下，一次或两次局部标本细菌培养所分离出来的皮肤菌群（SFOs）难以被区分是污染还是感染。人工关节置换的相关研究结果提示多次细菌培养可能有助于确定最终的诊断。但尚无研究探讨过在其它一些骨科植入物存在的情况下这样做是否有指导意义。本研究通过将术中所采集的标本量由1-2份增加到大于等于5份，同时延长细菌培养时间到10天以检测那些常规培养难以检测出的细菌，以此探讨微生物学诊断以及最终的抗生素治疗方案是否有所变化。
方法：通过对为期16个月的病例资料进行回顾性分析以确定符合研究条件的病例，包括：取除内固定者、非人工关节骨科植入物病例接受病灶清除冲洗者、因骨不连再次手术者、由原手术转变为人工关节置换者。本研究纳入标准为采集了5份组织标本，并分别以无菌器具对每份标本培养10天。SFOs包括凝固酶阴性的葡萄球菌、棒状杆菌、以及丙酸菌属。根据多次细菌培养的结果将所有病例划分为4组：（1）所有培养结果均为阴性，患者未接受抗生素治疗；（2）5份标本中至少1份培养出化脓性细菌（如金黄色葡萄球菌、假单胞菌等）者确定为化脓性感染；（3）至少3份标本培养出同一种SFO者诊断为SFO感染；以及（4）仅有1-2份标本培养出SFOs者诊断为SFO污染。抗生素治疗方案改变定义为由广谱抗生素更换为敏感抗生素，对SFO污染者不予抗生素治疗或以抗生素治疗SFO感染。
结果：共52例患者符合本研究纳入标准。其中21例患者的所有组织标本均未培养出细菌。有17例培养出化脓性细菌，但在这些病例中有26%的标本未能培养出化脓性细菌。因此多次培养结果确定了如果只进行一次培养就可能误诊的病例。本组病例中有7例患者最终确定为SFOs感染，而这些病例难以通过单次细菌培养得到确定。总共296份标本中共有14份（13例患者）培养出污染性SFOs，这表明2例被确定为SFO污染的患者如果只行1-2次培养就可能被误诊。总体而言，多次细菌培养改变了52例患者中13例的微生物学诊断结果（25%，95%可信区间：14-39%）。分别有4例化脓性细菌感染和5例SFO感染的患者根据培养结果选用了窄谱的敏感抗生素，另有2例SFO污染病例停用了抗生素。这表明根据多次细菌培养的结果，本研究中我们改变了52例患者中11例的术后抗生素治疗方案。
结论：与仅行1-2次细菌培养相比，5次或更多次细菌培养的结果增加了对细菌感染诊断的准确性，并改变了近1/4病例的术后抗生素治疗方案。

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The Impact of Multiple Cultures on Antibiotic Usage: A Protocol for Nonunion and Hardware Infections
INTRODUCTION
Skin flora organisms (SFOs) isolated from one or two biopsies in cases of fracture nonunion or possible deep implant infection are difficult to distinguish as contamination or infection. Prosthetic joint studies suggest multiple biopsies may help with definitive diagnosis. This has never been analyzed in cases with other orthopaedic implants. This study examined the change in microbiological diagnosis and resultant antibiotic treatment when the number of intra-operative biopsies was increased from 1-2 to ≥5 and incubation prolonged to 10 days to detect fastidious bacteria.
METHODS
A cohort of patient cases was constructed from a 16-month retrospective chart review. Patients undergoing either removal of hardware, irrigation and debridement with deep non-arthroplasty orthopaedic implant present, revision of nonunion, or conversion of prior surgery to total joint arthroplasty were identified. Inclusion criteria were five separate surgical biopsies, each cultured for 10 days (using separate sterile instruments). Coagulase negative Staphylococcus, Corynebacteria and Propionibacteria were defined as SFOs. Patients were categorized into four groups based upon the results of multiple cultures. Patients with (1) all cultures sterile and not treated for infection, (2) virulent infection defined as ≥1/5 biopsies growing a virulent organism (S.aureus, Pseudomonas, etc.), (3) SFO infection defined as ≥3 biopsies growing the same SFO or (4) SFO contaminant defined as one to two biopsies growing SFOs. Change in antibiotic treatment was defined as tailoring treatment from broad-spectrum coverage to organism specific coverage, avoiding treatment of a SFO contaminant or treating an SFO infection.
RESULTS
Fifty-two cases fulfilled inclusion criteria. In 21 cases, all biopsies were sterile. Seventeen cases grew virulent organism(s). However, virulent organisms were not grown in 26% of biopsies from these cases. Thus, multiple biopsies identified the virulent organism in four cases that could have been missed with one biopsy. Seven infections due to SFOs were definitively identified; that would not have been possible with one biopsy. Fourteen of 296 biopsies grew contaminant SFOs in 13 cases; thus, two patients were identified as having SFO contaminant that would not have been possible with only one to two biopsies. In summary, multiple biopsies changed microbiological diagnosis in 13/52 cases (25%, 95% Confidence Interval 14-39%). Antibiotic treatment was narrowed in four cases of virulent organism infection, targeted to an SFO infection in five cases and held in two cases of SFO contamination. In summary multiple biopsies changed postoperative antibiotic management in 11/52 cases (21%, 95% CI 11-25%) . {nextpage}
CONCLUSION
In comparison to one to two biopsies, five or more biopsies increased accuracy of diagnosis and altered post-operative antibiotic management in nearly one quarter of the cases.