Introduction. Bloodstream infections (BSI) are growing in incidence and present a serious health threat. Most patients wait up to 48 h before microbiological cultures can confirm a diagnosis. Low numbers of circulating bacteria in patients with BSI mean we need to develop new methods and optimize current methods to facilitate efficient recovery of bacteria from the bloodstream. This will allow detection of positive blood cultures in a more clinically useful timeframe. Many bacterial blood recovery methods are available and usually include a combination of techniques such as centrifugation, filtration, serum separation or lysis treatment. Here, we evaluate nine different bacteria recovery methods performed directly from blood culture. Aim. We sought to identify a bacterial recovery method that would allow for a cost-effective and efficient recovery of common BSI pathogens directly from blood culture. Methods. Simulated E. coli ATCC 25922 blood culture was used as a model system to evaluate nine different bacteria recovery methods. Each method was assessed on recovery yield, cost, hands-on time, risk of contamination and ease of use. The highest scoring recovery method was further evaluated using simulated blood cultures spiked with seven of the most frequently occurring bloodstream pathogens. The recovery yield was calculated based on c.f.u. count before and after each recovery method. Independent t-tests were performed to determine if the recovery methods evaluated were significantly different based on c.f.u. ml−1 log recovery. Results. All nine methods evaluated successfully recovered E. coli ATCC 25922 from simulated blood cultures although the bacterial yield differed significantly. The MALDI-TOF intact cell method offered the poorest recovery with a mean loss of 2.94±0.37 log c.f.u. ml−1. In contrast, a method developed by Bio-Rad achieved the greatest bacterial yield with a mean bacteria loss of 0.27±0.013 log c.f.u. ml−1. Overall, a low-speed serum-separation method was demonstrated to be the most efficient method in terms of time, cost and recovery efficiency and successfully recovered seven of the most frequent BSI pathogens with a mean bacteria loss of 0.717±0.18 log c.f.u. ml−1. Conclusion. The efficiency of bacterial recovery can vary significantly between different methods and thereby can have a critical impact on downstream analysis. The low-speed serum-separation method offered a simple and effective means of recovering common BSI pathogens from blood culture and will be further investigated for use in the rapid detection of bacteraemia and susceptibility testing in clinical practice.

中文翻译：

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改善血液培养中血液病原体的回收和检测。

介绍。血流感染（BSI）的发病率正在增加，并严重威胁健康。大多数患者在微生物培养可以确诊之前要等待48小时。BSI患者中循环细菌的数量较少，这意味着我们需要开发新方法并优化当前方法，以促进从血液中有效回收细菌。这将允许在临床上更有用的时间内检测到阳性血液培养物。有许多细菌血液回收方法可用，并且通常包括诸如离心，过滤，血清分离或裂解处理等技术的组合。在这里，我们评估了直接从血液培养中进行的9种不同的细菌回收方法。目标。我们试图确定一种细菌回收方法，该方法可直接从血液培养物中经济高效地回收常见的BSI病原体。方法。模拟的大肠杆菌ATCC 25922血液培养用作模型系统，以评估九种不同的细菌回收方法。对每种方法的回收率，成本，动手时间，污染风险和易用性进行了评估。使用掺有最常见的七种血液病原体的模拟血液培养物进一步评估了最高得分的恢复方法。根据每种回收方法之前和之后的cfu计数计算回收率。独立t 进行了测试，以确定评估的恢复方法是否基于cfu ml - 1日志恢复显着不同。结果。评估的所有九种方法均能从模拟血液培养物中成功回收大肠杆菌ATCC 25922，尽管细菌产量差异显着。MALDI-TOF完整细胞方法提供的回收率最差，平均损失为2.94±0.37 log cfu ml -1。相反，由Bio-Rad开发的方法获得了最大的细菌产量，平均细菌损失为0.27±0.013 log cfu ml -1 。总体而言，低速血清分离方法被证明是在时间，成本方面和回收效率的最有效的方法，成功地回收的最频繁的BSI病原体七连0.717±0.18日志菌落ml的平均细菌损失- 1。结论。细菌回收的效率在不同方法之间可能会有很大差异，因此可能对下游分析产生重大影响。低速血清分离法提供了一种从血液培养物中回收常见BSI病原体的简单有效方法，并将进一步研究其在临床实践中对菌血症的快速检测和药敏试验中的应用。