State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, , Hong Kong, China.
J Clin Pathol. 2014 Apr;67(4):361-6. doi: 10.1136/jclinpath-2013-201818. Epub 2013 Oct 18.
Although the revolutionary matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) has been evaluated for identification of various groups of bacteria, its application in bacteria that are 'difficult-to-identify' by phenotypic tests has been less well studied. We aim to evaluate the usefulness of MALDI-TOF MS for identification of 'difficult-to-identify' bacterial isolates.
We evaluated the performance of the Bruker MALDI-TOF MS system for a collection of 67 diverse clinically important bacterial isolates that were less commonly encountered, possessed ambiguous biochemical profiles or belonged to newly discovered species. The results were compared with 16S rRNA gene sequencing as a reference method for species identification.
Using 16S rRNA gene sequencing as the reference method, 30 (45%) isolates were identified correctly to species level (score ≥2.0), 20 (30%) were only identified to genus level (score ≥1.7), four (6%) were misidentified (incorrect species with score ≥2.0 or incorrect genus with score ≥1.7) and 13 (19%) showed 'no identification' (score <1.7). Aerobic Gram-positive bacteria showed the highest percentage of correct species identification, followed by aerobic Gram-negative, anaerobic Gram-positive and anaerobic Gram-negative bacteria. Sixteen isolates identified to genus level actually showed the correct species but with scores below the threshold for species identification. Most isolates which showed 'no identification' were due to the absence of the corresponding species in the Bruker database.
Expansion of commercial databases to include reference spectra of less commonly encountered and newly discovered species and to increase available spectra for each species is required to improve the accuracy of MALDI-TOF MS for identifying 'difficult-to-identify' bacteria.
尽管革命性的基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)已被评估用于鉴定各种细菌群,但它在通过表型试验难以鉴定的细菌中的应用研究较少。我们旨在评估 MALDI-TOF MS 对鉴定“难以鉴定”细菌分离株的有用性。
我们评估了 Bruker MALDI-TOF MS 系统对一组 67 种不同的临床重要细菌分离株的性能,这些分离株较不常见,具有模糊的生化特征或属于新发现的物种。结果与 16S rRNA 基因测序作为物种鉴定的参考方法进行了比较。
使用 16S rRNA 基因测序作为参考方法,30(45%)个分离株被正确鉴定到种水平(得分≥2.0),20(30%)个分离株仅鉴定到属水平(得分≥1.7),4(6%)个分离株被错误鉴定(得分≥2.0 的错误物种或得分≥1.7 的错误属),13(19%)个分离株显示“无法鉴定”(得分<1.7)。需氧革兰氏阳性菌显示出最高的正确种鉴定百分比,其次是需氧革兰氏阴性菌、厌氧革兰氏阳性菌和厌氧革兰氏阴性菌。16 个鉴定到属水平的分离株实际上显示了正确的物种,但得分低于物种鉴定的阈值。大多数显示“无法鉴定”的分离株是由于 Bruker 数据库中缺少相应的物种。
需要扩展商业数据库,包括较少遇到和新发现的物种的参考光谱,并增加每个物种的可用光谱,以提高 MALDI-TOF MS 鉴定“难以鉴定”细菌的准确性。