血培养凝固酶阴性葡萄球菌阳性的评价

Evaluation of Coagulase-Negative Staphylococci in Blood Culture

目的调查血培养中凝固酶阴性的葡萄球菌(CNS)血样本的污染率。方法回顾分析2004-2006年从本院住院患者血中分离到CNS的病例共97例,判定是菌血症还是血样本污染。结果48/97(49.5%)的病例为菌血症,其中24例(50.0%)原发入侵部位为静脉插管及外来异物,8例(16.7%)为术后伤口感染,5例(10.4%)来自呼吸道,5例(10.4%)来自脐带,1例来自眼,5例来源不明。这48例主要来自重症监护病房、新生儿病房、外科病房和血液病房。48h内检测出的CNS中,有24株(35.8%)为污染菌,48h以后检出的CNS,全部为污染菌(16株);污染菌的检测时间明显长于病原菌的检测时间(P<0.01)。病原菌与污染菌对青霉素、苯唑西林、庆大霉素、环丙沙星、万古霉素的耐药性无显著差异(P>0.25)。在24例由静脉插管及外来异物引起的菌血症中,19例拔除导管后,菌血症得到控制;5例同时还使用了万古霉素,菌血症才得到控制。结论CNS菌血症血样本的污染率较高,应当综合临床和实验室的资料判定是否为污染,避免不必要地使用抗微生物药物,特别是万古霉素。

Objective To investigate the contamination incidence of coagulase - negative staphylococci （CNS） in blood culture. Methods Retrospectively analyze coagulase -negative staphylococci in blood culture from 97 hospitalized patients at our Hospital from 2004 to 2006. We differentiated true bacteremia from contamination by using a criterion reviewed from published papers. Results 48/97（49.5% ） of cases was bacteremia due to CNS. 24 strains （50. 0% ） were related to catheters using and foreign bodies, 8 （ 16. 7% ） related to postoperative wounds, 5 （ 10. 4% ） related to breath way, 5 （ 10. 4% ） related to umbilicus, 1 related to eye infection. The rest 5 strains were unkown. Most of 48 cases of bacteremia were from intensive care units, neonatal ward, surgeon wards and hematology ward. 24 strains from 67 of CNS （35.8%） isolated from bloodstream within 49 hours, All 16 strains isolated after 48 hours were contaminants. The time to positive for contaminants was significantly longer than that for true pathogens （32.2 h/20.6h, P 〈 0. 01 ）. The resistance to penicillin, oxacillin, gentamicin ciprofloxacin and vancomycin were no significant difference between contaminants and pathogens （ P 〉 0. 25 ）. 19 of 24 cases of true bacteremia due to catheters and foreign bodies were cured after only removal of catheters and foreign bodies, and the rest 5 cases were cured by both administering vancomycin and removing catheters. Conclusion The contamination incidence of CNS in blood culture was relatively high. We should determine true bacteremia from contamination by reviewing the clinical, epidemiological and laboratory information, which would be helpful to avoid abuse of antimicrobials, especially vancomycin.