Hansen D S, Jensen A G, Nørskov-Lauritsen N, Skov R, Bruun B
Department of Clinical Microbiology, Statens Serum Institut, Copenhagen, Denmark.
Clin Microbiol Infect. 2002 Jan;8(1):38-44. doi: 10.1046/j.1469-0691.2002.00372.x.
To study the possibility of reporting results of identification and susceptibility testing of Gram-negative bacilli the same day as bacteremia is detected by using direct inoculation from positive blood cultures (Bactec 9240) into VITEK GNI+ and GNS-GA cards.
All blood cultures with Gram-negative enteric bacillus-like morphology on microscopy found to be positive on workdays between 15 June 1999 and 29 February 2000 were included. Identification and susceptibility testing were done by three methods: the direct method using a suspension made by differential centrifugation of positive blood culture broth for inoculation of the VITEK cards; the standard method using an inoculum made from an overnight culture on a solid media; and the routine method (reference method) using conventional testing.
Of 169 isolates, the direct method resulted in 75% correct identifications, 9% misidentifications and 17% non-identifications. All misidentified isolates were Escherichia coli, of which 80% were reported as Salmonella arizonae. Five biochemical tests yielded most of the aberrant results; correcting the citrate and malonate reactions in most cases led to correct identification by the VITEK database. Despite a negative H2S reaction, 11 E. coli isolates were reported as S. arizonae. Two-thirds (69%) of identifications were reported within 6 h, and 95% of these were correct. The direct susceptibility testing method was assessable for 140 isolates. Correct results were found in 99% of isolate-antimicrobial combinations, and 85% were reported within 6 h.
The direct VITEK method could correctly report identifications and susceptibility patterns within 6 h, making same-day reporting possible for almost two-thirds (63%) of bacteremic episodes with Gram-negative bacilli. These results could probably be improved by modification of the identification algorithms of the VITEK software.
研究通过将阳性血培养物（Bactec 9240）直接接种到VITEK GNI+和GNS-GA卡中，在检测到菌血症当天报告革兰氏阴性杆菌鉴定和药敏试验结果的可能性。
纳入1999年6月15日至2000年2月29日工作日期间镜检显示革兰氏阴性肠道杆菌样形态且血培养呈阳性的所有样本。采用三种方法进行鉴定和药敏试验：直接法，使用通过对阳性血培养肉汤进行差速离心制备的悬液接种VITEK卡；标准法，使用由固体培养基上的过夜培养物制备的接种物；常规法（参考法），使用传统检测方法。
在169株分离株中，直接法的正确鉴定率为75%，错误鉴定率为9%，无法鉴定率为17%。所有错误鉴定的分离株均为大肠杆菌，其中80%被报告为亚利桑那沙门氏菌。五项生化试验产生了大多数异常结果；在大多数情况下校正柠檬酸盐和丙二酸盐反应可导致VITEK数据库正确鉴定。尽管硫化氢反应为阴性，但11株大肠杆菌分离株被报告为亚利桑那沙门氏菌。三分之二（69%）的鉴定结果在6小时内报告，其中95%是正确的。直接药敏试验方法可用于140株分离株。99%的分离株-抗菌药物组合结果正确，85%在6小时内报告。
直接VITEK法可在6小时内正确报告鉴定结果和药敏模式，使近三分之二（63%）革兰氏阴性杆菌菌血症发作能够当天报告。通过修改VITEK软件的鉴定算法，这些结果可能会得到改善。
