Special Pathogens Laboratory, Pittsburgh, PA, United States of America.
Microbiology Department, Freeman Hospital, Newcastle upon Tyne, United Kingdom.
PLoS One. 2021 Mar 3;16(3):e0247166. doi: 10.1371/journal.pone.0247166. eCollection 2021.
Nontuberculous mycobacteria (NTM) are waterborne pathogens commonly found in building water systems where they are a primary concern to vulnerable patient populations and can cause severe disease. The recovery of NTM from environmental samples can be a laborious undertaking and current pre-treatment methods and selective media lack sensitivity. We explored the use of the highly selective Rapidly Growing Mycobacteria (RGM) medium for culturing NTM from environmental water samples compared to existing methods. In total, 223 environmental water samples, including potable and non-potable water, were cultured for NTM using three culture media. In addition to direct culture on RGM medium, each sample was cultured on Middlebrook 7H10 medium and Mitchison 7H11 medium after pre-treatment with 0.2M KCl-HCl. Additionally, 33 distinct species of NTM were inoculated onto RGM medium and 7H10 medium in parallel to directly compare their growth. The use of RGM medium alone without pre-treatment provided a sensitivity (91%) comparable to that offered by culture on both 7H10 and 7H11 with acid pretreatment (combined sensitivity; 86%) with significantly less overgrowth and interference from other organisms on RGM medium. The average concentration of NTM observed on RGM medium alone was comparable to or greater than the NTM concentration on either medium alone or combined. Thirty-three species were examined in parallel and all tested strains of 27 of these species successfully grew on RGM medium, including 19 of 21 from the CDC's healthcare-associated infections species list. RGM medium was successful at recovering environmental NTM without a pre-treatment, greatly reducing labor and materials required to process samples. Simplification of culture processing for environmental NTM will allow for a better assessment of their presence in building water systems and the potential for reduced exposure of susceptible populations.
非结核分枝杆菌（NTM）是一种水生病原体，通常存在于建筑物的供水系统中，对脆弱的患者群体构成主要威胁，并可导致严重疾病。从环境样本中回收 NTM 是一项费力的工作，目前的预处理方法和选择性培养基缺乏敏感性。我们探讨了使用高度选择性的快速生长分枝杆菌（RGM）培养基从环境水样中培养 NTM 的方法，并与现有方法进行了比较。总共培养了 223 个环境水样，包括饮用水和非饮用水，使用三种培养基培养 NTM。除了直接在 RGM 培养基上培养外，每个样本在预处理 0.2M KCl-HCl 后分别在 Middlebrook 7H10 培养基和 Mitchison 7H11 培养基上培养。此外，将 33 种不同的 NTM 种接种到 RGM 培养基和 7H10 培养基上，以直接比较它们的生长。单独使用 RGM 培养基而不进行预处理，其敏感性（91%）与用酸预处理的 7H10 和 7H11 培养基联合培养（综合敏感性；86%）相当，RGM 培养基上的过度生长和其他生物体的干扰明显减少。单独使用 RGM 培养基观察到的 NTM 平均浓度与单独使用任何一种培养基或联合使用的 NTM 浓度相当或更高。33 种物种同时进行了平行检测，所有 27 种受试菌株都能在 RGM 培养基上成功生长，其中包括疾病预防控制中心的医疗保健相关感染物种列表中的 21 种中的 19 种。RGM 培养基无需预处理即可成功回收环境 NTM，大大减少了处理样品所需的劳动力和材料。简化环境 NTM 的培养处理将有助于更好地评估它们在建筑物供水系统中的存在情况，并减少易感人群暴露的风险。
