Centre for Infectious Diseases and Microbiology Laboratory Services, Institute of Clinical Pathology and Medical Research, Westmead Hospital, Westmead, New South Wales, Australia.
PLoS One. 2011;6(8):e23285. doi: 10.1371/journal.pone.0023285. Epub 2011 Aug 16.
Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) is a novel method for the direct identification of bacteria from blood culture broths. We evaluate for the first time, the performance of the MALDI Sepsityper™ Kit and MS for the identification of bacteria compared to standard phenotypic methods using the manufacturer's specified bacterial identification criteria (spectral scores ≥1.700-1.999 and ≥2.000 indicated identification to genus and species level, respectively). Five hundred and seven positive blood culture broths were prospectively examined, of which 379 (74.8%; 358 monomicrobial, 21 polymicrobial) were identified by MALDI-TOF MS; 195 (100%) and 132 (67.7%) of 195 gram-positive; and 163 (100%) and 149 (91.4%) of 163 gram-negative organisms from monomicrobial blood cultures were correctly identified to genus and species level, respectively. Spectral scores <1.700 (no identification) were obtained in 128/507 (25.2%) positive blood culture broths, including 31.6% and 32.3% of gram-positive and polymicrobial blood cultures, respectively. Significantly more gram-negative organisms were identified compared to gram-positive organisms at species level (p<0.0001). Five blood cultures were misidentified, but at species level only; including four monomicrobial blood cultures with Streptococcus oralis/mitis that were misidentified as Streptococcus pneumoniae. Positive predictive values for the direct identification of both gram-positive and gram-negative bacteria from monomicrobial blood culture broths to genus level were 100%. A diagnostic algorithm for positive blood culture broths that incorporates gram staining and MALDI-TOF MS should identify the majority of pathogens, particularly to genus level.
基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）是一种直接从血培养肉汤中鉴定细菌的新方法。我们首次评估了 MALDI Sepsityper™试剂盒和 MS 与标准表型方法相比的性能，使用制造商规定的细菌鉴定标准（光谱评分≥1.700-1.999 和≥2.000 分别表示鉴定到属和种水平）。前瞻性检查了 507 份阳性血培养肉汤，其中 379 份（74.8%；358 份为单一致病菌，21 份为多致病菌）通过 MALDI-TOF MS 鉴定；195 份（100%）和 132 份（67.7%）革兰阳性菌；163 份（100%）和 149 份（91.4%）革兰阴性菌分别正确鉴定到属和种水平。128/507（25.2%）份阳性血培养肉汤的光谱评分<1.700（无法鉴定），其中革兰阳性菌和多致病菌的比例分别为 31.6%和 32.3%。与革兰阳性菌相比，革兰阴性菌在种水平上的鉴定率明显更高（p<0.0001）。有 5 份血培养被误鉴定，但仅限于种水平；包括 4 份单一致病菌的血培养被误鉴定为肺炎链球菌。直接鉴定革兰阳性和革兰阴性菌单一致病菌血培养肉汤到属水平的阳性预测值均为 100%。一种包含革兰染色和 MALDI-TOF MS 的阳性血培养肉汤诊断算法，应该能够识别出大多数病原体，特别是在属水平。
