RATIONALE Lipids are important mycobacterium cell wall constituents; changes are linked with drug resistance. Liquid extraction surface analysis (LESA) enables direct sampling in a highly sensitive manner. Here we describe protocols for the analysis of lipids from bacterial colonies. Lipids form various adducts, complicating spectra. Salt additives were investigated to circumvent this problem. METHODS Chloroform:methanol mixtures were studied for lipid extraction and analysis by LESA-MS. The inclusion of (ESI-compatible) acetate salts of sodium, potassium or lithium in the extraction solvent was investigated. RESULTS We report the detection of bacterial cell wall lipids from mycobacterial species using LESA for the first time. Sampling protocols were optimised for the use of volatile extraction solvents. The inclusion of acetate salt additives in the sampling solvent significantly reduces spectral complexity in comparison with no additives being used. CONCLUSIONS LESA offers a sensitive technique for bacterial lipid phenotyping. The inclusion of an acetate salt in the sampling solvent drives adduct formation towards a specific adduct type and thus significantly reduces spectral complexity.

中文翻译：

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分枝杆菌细胞壁脂质的直接液体萃取表面分析质谱：盐添加剂，可降低光谱复杂性。

理性因素脂质是重要的分枝杆菌细胞壁成分。变化与耐药性有关。液体萃取表面分析（LESA）能够以高度灵敏的方式直接取样。在这里，我们描述了用于分析细菌菌落中脂质的方案。脂质形成各种加合物，使光谱复杂化。研究了盐添加剂来解决这个问题。方法采用LESA-MS法研究了氯仿：甲醇混合物的脂质提取和分析。研究了萃取溶剂中钠，钾或锂的（ESI兼容）乙酸盐的含量。结果我们首次报道了使用LESA检测到分枝杆菌属细菌细胞壁脂质的方法。针对使用挥发性提取溶剂的采样方案进行了优化。与不使用添加剂相比，采样溶剂中包含乙酸盐添加剂会大大降低光谱复杂性。结论LESA为细菌脂质表型提供了一种灵敏的技术。采样溶剂中包含乙酸盐会促使加合物形成特定的加合物类型，从而显着降低光谱复杂性。