Peretz A, Isakovich N, Pastukh N, Koifman A, Glyatman T, Brodsky D
Clinical Microbiology Laboratory, Baruch Padeh Medical Center, Poriya, Affiliated with the Faculty of Medicine, Bar-Ilan University, Galilee, Israel,
Eur J Clin Microbiol Infect Dis. 2015 Aug;34(8):1539-41. doi: 10.1007/s10096-015-2383-0. Epub 2015 Apr 16.
Blood is one of the most important specimens sent to a microbiology laboratory for culture. Most blood cultures are incubated for 5-7 days, except in cases where there is a suspicion of infection caused by microorganisms that proliferate slowly, or infections expressed by a small number of bacteria in the bloodstream. Therefore, at the end of incubation, misidentification of positive cultures and false-negative results are a real possibility. The aim of this work was to perform a confirmation by Gram staining of the lack of any microorganisms in blood cultures that were identified as negative by the BACTEC™ FX system at the end of incubation. All bottles defined as negative by the BACTEC FX system were Gram-stained using an automatic device and inoculated on solid growth media. In our work, 15 cultures that were defined as negative by the BACTEC FX system at the end of the incubation were found to contain microorganisms when Gram-stained. The main characteristic of most bacteria and fungi growing in the culture bottles that were defined as negative was slow growth. This finding raises a problematic issue concerning the need to perform Gram staining of all blood cultures, which could overload the routine laboratory work, especially laboratories serving large medical centers and receiving a large number of blood cultures.
血液是送往微生物学实验室进行培养的最重要标本之一。大多数血培养需孵育5 - 7天，但怀疑由生长缓慢的微生物引起感染或血流中细菌数量较少导致的感染情况除外。因此，在孵育结束时，阳性培养物的错误鉴定和假阴性结果确实有可能出现。这项工作的目的是通过革兰氏染色对孵育结束时被BACTEC™ FX系统鉴定为阴性的血培养物中是否存在任何微生物进行确认。所有被BACTEC FX系统定义为阴性的瓶子都使用自动设备进行革兰氏染色，并接种到固体生长培养基上。在我们的工作中，发现15份在孵育结束时被BACTEC FX系统定义为阴性的培养物经革兰氏染色后含有微生物。在被定义为阴性的培养瓶中生长的大多数细菌和真菌的主要特征是生长缓慢。这一发现引发了一个关于是否需要对所有血培养物进行革兰氏染色的问题，这可能会使常规实验室工作负担过重，尤其是为大型医疗中心服务且接收大量血培养物的实验室。
