Non-specific, agar medium-related peaks can result in false positive Mycoplasma alkalescens and Mycoplasma arginini identification by MALDI-TOF MS
Non-specific, agar medium-related peaks can result in false positive Mycoplasma alkalescens and Mycoplasma arginini identification by MALDI-TOF MS
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DOI：
10.1016/j.rvsc.2020.03.010
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发表时间：
2020-06-01
影响因子：
2.4
通讯作者：
Boyen, Filip
中科院分区：
文献类型：
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作者：
Bokma, Jade;Pardon, Bart;Boyen, Filip
MALDI-TOF MS 是一种快速、准确地识别液体培养基中支原体种类的工具。然而，当试图从固体培养基中鉴定假定的牛支原体（M. bovis）菌落（“直接转移法”）时，观察到精氨酸支原体和碱性支原体鉴定的出现率惊人地高。据推测，琼脂培养基成分与支原体属的假阳性鉴定有关，因为牛支原体菌落非常小并且会生长到琼脂中。本研究的目的是确定完全改良的胸膜肺炎样生物 (PPLO) 琼脂（补充有马血清、丙酮酸钠、工业酵母提取物、氨苄青霉素钠盐和粘菌素）及其单独成分是否会导致错误鉴定为支原体属。通过 MALDI-TOF MS。总共检查了 100 个样品，其中 33% 的修饰 PPLO 琼脂斑点被鉴定为 M. alkalescens (16%) 和 M. arginini (17%)），尽管分值相对较低（< 1.85）。没有获得牛分枝杆菌的错误鉴定。几种培养基成分（未补充的 PPLO 琼脂、马血清和粘菌素）产生的光谱峰与 M. alkalescens 和 M. arginini 数据库光谱中存在的峰非常匹配。这项研究表明，应谨慎解释直接转移方法，从含有 PPLO 琼脂、马血清和/或粘菌素的固体培养基中取样支原体样菌落时，应尽量挑选尽可能少的琼脂。
MALDI-TOF MS is a fast and accurate tool to identify Mycoplasma species in liquid media. However, when trying to identify presumptive Mycoplasma bovis (M. bovis) colonies from solid medium (the "direct transfer method") a surprisingly high occurrence of M. arginini and M. alkalescens identification was observed. It was hypothesized that agar medium components are associated with false positive identification with Mycoplasma spp., as M. bovis colonies are very small and grow into the agar. The objective of this study was to determine whether complete modified pleuropneumonia-like organism (PPLO) agar (supplemented with horse serum, sodium pyruvate, technical yeast extract, ampicillin sodium salt and colistin) and the separate components, result in false identification as Mycoplasma spp. by MALDI-TOF MS. A total of 100 samples were examined, of which 33% of the modified PPLO agar spots were identified as M. alkalescens (16%) and M. arginini (17%)), albeit with relatively low score values ( < 1.85). No false identification of M. bovis was obtained. Several medium components (unsupplemented PPLO agar, horse serum and colistin) resulted in spectra with peaks showing close matches with peaks present in the M. alkalescens and M. arginini database spectra. This study shows that the direct transfer method should be interpreted with caution, and one should strive to pick as little as possible agar when sampling Mycoplasma-like colonies from solid medium containing PPLO agar, horse serum and/or colistin.