Currently, the capability of identification for Acinetobacter species using MALDI-TOF MS still remains unclear in clinical laboratories due to certain elusory phenomena. Thus, we conducted this research to evaluate this technique and reveal the causes of misidentification. Briefly, a total of 788 Acinetobacter strains were collected and confirmed at the species level by 16S rDNA and rpoB sequencing, and subsequently compared to the identification by MALDI-TOF MS using direct smear and bacterial extraction pretreatments. Cluster analysis was performed based on the mass spectra and 16S rDNA to reflect the diversity among different species. Eventually, 19 Acinetobacter species were confirmed, including 6 species unavailable in Biotyper 3.0 database. Another novel species was observed, temporarily named A. corallinus. The accuracy of identification for Acinetobacter species using MALDI-TOF MS was 97.08% (765/788), regardless of which pretreatment was applied. The misidentification only occurred on 3 A. parvus strains and 20 strains of species unavailable in the database. The proportions of strains with identification score ≥ 2.000 using direct smear and bacterial extraction pretreatments were 86.04% (678/788) and 95.43% (752/788), χ² = 41.336, P < 0.001. The species similar in 16 rDNA were discriminative from the mass spectra, such as A. baumannii & A. junii, A. pittii & A. calcoaceticus, and A. nosocomialis & A. seifertii. Therefore, using MALDI-TOF MS to identify Acinetobacter strains isolated from clinical samples was deemed reliable. Misidentification occurred occasionally due to the insufficiency of the database rather than sample extraction failure. We suggest gene sequencing should be performed when the identification score is under 2.000 even when using bacterial extraction pretreatment.

中文翻译：

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在临床实验室中通过基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）鉴定不动杆菌属的见解

目前，由于某些难以捉摸的现象，在临床实验室中仍不清楚使用MALDI-TOF MS鉴定不动杆菌的能力。因此，我们进行了这项研究以评估该技术并揭示错误识别的原因。简而言之，共收集了788株不动杆菌菌株，并通过16S rDNA和rpoB测序在物种水平上进行了确认，随后与使用直接涂片和细菌提取预处理的MALDI-TOF MS进行了鉴定。基于质谱和16S rDNA进行聚类分析以反映不同物种之间的多样性。最终，有19种不动杆菌已确认物种，包括Biotyper 3.0数据库中不可用的6种。观察到另一种新物种，暂时命名为A.corallinus。无论采用哪种预处理，使用MALDI-TOF MS鉴定不动杆菌属的准确性为97.08％（765/788）。错误识别仅发生在数据库中没有的3株小曲霉菌株和20株物种中。使用直接涂片和细菌提取的预处理与识别得分≥2.000菌株的比例分别为86.04％（788分之678）和95.43％（788分之752），χ ²  = 41.336，P  <0.001。16 rDNA中相似的物种来自质谱判别，如鲍曼不动杆菌＆A.琼氏，A. pittii＆A. calcoaceticus，和A. nosocomialis＆A. seifertii。因此，使用MALDI-TOF MS鉴定从临床样品中分离出的不动杆菌菌株被认为是可靠的。错误识别有时是由于数据库不足而不是样本提取失败而引起的。我们建议，即使使用细菌提取预处理，当鉴定得分低于2.000时，也应进行基因测序。