Martínez J A, Pozo L, Almela M, Marco F, Soriano A, López F, Balasso V, Aguilar J, Mensa J
Department of Infectious Diseases, Hospital Clinic, IDIBAPS, University of Barcelona, Spain.
Clin Microbiol Infect. 2007 Jul;13(7):709-16. doi: 10.1111/j.1469-0691.2007.01736.x. Epub 2007 May 2.
Time-to-positivity is useful in the diagnosis of catheter-related bacteraemia and as a predictor of an endovascular source in patients with Staphylococcus aureus bacteraemia. However, this parameter has been evaluated for only a limited number of microorganisms. In the present study, time-to-positivity was recorded for 1872 episodes of significant monomicrobial bacteraemia diagnosed at a teaching hospital during a 2-year period, and the associated microbial and clinical variables were investigated. According to multivariate analysis, Streptococcus pneumoniae, beta-haemolytic streptococci, Escherichia coli, Klebsiella, Enterobacter, Citrobacter and Aeromonas were characterised by fast growth, with an endovascular source, shock, liver cirrhosis and neutropenia also predicting a short time-to-positivity. For patients not receiving appropriate antibiotics, detection of Gram-positive cocci in clusters within 14 h was predictive of Staph. aureus; a time-to-positivity of >21 h ruled out the possibility that a Gram-positive organism in chains was a beta-haemolytic streptococcus or Strep. pneumoniae, and a time-to-positivity of < or =12 h meant that it was very unlikely that a Gram-negative bacillus was a non-fermenter. A time-to-positivity of < or =8 h was predictive of a non-urinary tract source in patients with E. coli bacteraemia, and detection of growth within 13 h predicted an endovascular source in those with Staph. aureus bacteraemia. In conclusion, time-to-positivity depended on the microorganism, original source and clinical variables involved. Although this measurement may provide some early clues concerning the microorganisms involved and the source of bacteraemia, its clinical impact remains to be defined.
阳性时间对于导管相关菌血症的诊断以及金黄色葡萄球菌菌血症患者血管内感染源的预测具有重要价值。然而，仅对有限数量的微生物评估了该参数。在本研究中，记录了一家教学医院在两年期间诊断出的1872例显著单微生物菌血症发作的阳性时间，并对相关的微生物和临床变量进行了调查。多因素分析显示，肺炎链球菌、β溶血性链球菌、大肠杆菌、克雷伯菌属、肠杆菌属、柠檬酸杆菌属和气单胞菌属具有生长迅速的特点，血管内感染源、休克、肝硬化和中性粒细胞减少也预示着阳性时间较短。对于未接受适当抗生素治疗的患者，14小时内检测到成堆的革兰氏阳性球菌提示为金黄色葡萄球菌；阳性时间>21小时可排除链状革兰氏阳性菌为β溶血性链球菌或肺炎链球菌的可能性，阳性时间≤12小时意味着革兰氏阴性杆菌极不可能是非发酵菌。大肠杆菌菌血症患者阳性时间≤8小时提示非泌尿道感染源，金黄色葡萄球菌菌血症患者13小时内检测到细菌生长提示血管内感染源。总之，阳性时间取决于所涉及的微生物、原始感染源和临床变量。尽管该测量可能提供一些有关所涉及微生物和菌血症感染源的早期线索，但其临床影响仍有待确定。
