Abstract：
Precise and rapid methods are needed to improve monitoring approaches of L. pneumophila (Lp) in cooling towers (CTs) to allow timely operational adjustments and prevent outbreaks. The performance of liquid culture (ASTM D8429-21) and an online qPCR device were first compared to conventional filter plate culture (ISO 11731-2017), qPCR and semi-automated qPCR at three spiked concentrations of Lp (serogroup 1) validated by flow cytometry (total/viable cell count). The most accurate was qPCR, followed by liquid culture, online and semi-automated qPCR, and lastly, by a significant margin, filter plate culture. An industrial CT system was monitored using liquid and direct plate culture by the facility, qPCR and online qPCR. Direct plate and liquid culture results agreed at regulatory sampling point, supporting the use of the faster liquid culture for monitoring culturable Lp. During initial operation, qPCR and online qPCR results were within one log of culture at the primary pump before deviating after first cleaning. Other points revealed high spatial variability of Lp. The secondary pumps and chiller had the most positivity and highest concentrations by both qPCR and liquid culture compared to the basin and infeed tank. Altogether, this suggests that results from monthly compliance sampling at a single location with plate culture are not representative of Lp risks in this CT due to the high temporal and spatial variability. The primary pump, rather than the CT basin, should be designated for sampling, as it is representative of the health risk. An annual multi point survey of the system should be conducted to identify and target Lp hot spots. Generally, a combination of liquid culture for compliance and frequent qPCR for process control provides a more agile and robust monitoring scheme than plate culture alone, enabling early treatment adjustments, due to lower limit of detection (LOD) and turnover time.
摘要：
需要精确和快速的方法来改进冷却塔(CT)中嗜肺乳杆菌(Lp)的监测方法,以允许及时的操作调整和防止爆发。首先将液体培养（ASTMD8429-21）和在线qPCR装置的性能与常规过滤板培养（ISO11731-2017）进行比较，通过流式细胞术(总/活细胞计数)验证在三个加标浓度的Lp(血清群1)下的qPCR和半自动qPCR。最准确的是qPCR，其次是液体培养，在线和半自动化qPCR，最后，以显著的优势，过滤板培养。该设施使用液体和直接平板培养来监测工业CT系统，qPCR和在线qPCR。直接平板和液体培养结果在监管采样点一致，支持使用更快的液体培养物监测可培养的Lp。在初始操作期间，qPCR和在线qPCR结果在第一次清洁后偏离之前在初级泵处的培养物的一个对数内。其他点显示Lp的高度空间变异性。与盆和进料罐相比,通过qPCR和液体培养,二级泵和冷却器具有最大的阳性和最高的浓度。总之,这表明,由于时间和空间变异性较高,因此在该CT中,在单个位置进行每月依从性采样并采用平板培养的结果不代表Lp风险.主泵,而不是CT盆地，应指定取样，因为它是健康风险的代表。应进行系统的年度多点调查，以识别和瞄准Lp热点。一般来说,液体培养的合规性和频繁的qPCR过程控制的组合提供了一个更敏捷和强大的监测方案比单独的平板培养，能够早期调整治疗，由于检测限(LOD)和周转时间较低。
