Department of Public Health and Pediatrics, University of Turin, Turin, Italy.
Department of Public Health and Pediatrics, University of Turin, Turin, Italy.
J Hosp Infect. 2020 Mar;104(3):365-373. doi: 10.1016/j.jhin.2019.10.010. Epub 2019 Oct 16.
Invasive non-tuberculous mycobacteria (NTM) infections are emerging worldwide in patients undergoing open-chest cardiac bypass surgery exposed to contaminated heater-cooler units (HCUs). Although this outbreak has been investigated by culturing bacteria isolated from HCU aerosol and water samples, these conventional methods have low-analytic sensitivity, high rates of sample contamination, and long turnaround time.
To develop a simple and effective method to detect NTM in HCUs by real-time polymerase chain reaction (PCR), with a short laboratory turnaround time and reliable culture results.
A total of 281 water samples collected from various HCUs at seven Italian hospitals were simultaneously screened for NTM by a propidium monoazide (PMA)-PCR assay and by conventional culture testing. The results were analysed with culture testing as the reference method.
(i) The agreement between culture testing and PMA-PCR was 85.0% with a cycle threshold (C) cut-off value of <38 vs 80.0% with a C of <43, with a moderate Cohen's κ-coefficient; (ii) the C cut-off value of <42 was deemed more suitable for predicting positive specimens; (iii) given the low concentration of target DNA in water samples, the minimum volume to be tested was 1 L.
The use of PMA-PCR for fast detection of NTM from environmental samples is highly recommended in order to ascertain whether HCUs may represent a potential source of human exposure to NTM. This reliable and simple method reduces laboratory turnaround time compared to conventional methods (one to two days vs eight weeks, respectively), thereby improving control strategies and effective management of HCUs.
在接受开胸心脏旁路手术的患者中，暴露于受污染的热交换器单元（HCU）的情况下，全球范围内侵袭性非结核分枝杆菌（NTM）感染正在出现。尽管已经通过培养从 HCU 气溶胶和水样中分离的细菌对该爆发进行了调查，但这些传统方法的分析灵敏度低、样本污染率高且周转时间长。
通过实时聚合酶链反应（PCR）开发一种简单有效的方法，从 HCU 中检测 NTM，该方法具有较短的实验室周转时间和可靠的培养结果。
对意大利七家医院的 281 个来自不同 HCU 的水样同时进行 PMA-PCR 检测和常规培养检测，以筛查 NTM。以培养检测作为参考方法对结果进行分析。
（i）培养检测与 PMA-PCR 的一致性为 85.0%，C 阈值（C）<38 时为 80.0%，C<43 时为 80.0%，中等 Cohen's κ 系数；（ii）C<42 的截止值更适合预测阳性标本；（iii）鉴于水样中目标 DNA 的浓度低，建议最小检测体积为 1 L。
强烈建议使用 PMA-PCR 快速检测环境样本中的 NTM，以确定 HCU 是否可能成为人类暴露于 NTM 的潜在来源。与传统方法（分别为一到两天和八周）相比，这种可靠且简单的方法可缩短实验室周转时间，从而改善 HCU 的控制策略和有效管理。
