Jeverica Samo, Nagy Elisabeth, Mueller-Premru Manica, Papst Lea
Institute of Microbiology and Immunology, Medical Faculty, University of Ljubljana, Ljubljana, Slovenia.
Institute of Clinical Microbiology, University of Szeged, Szeged, Hungary.
Anaerobe. 2018 Dec;54:231-235. doi: 10.1016/j.anaerobe.2018.05.003. Epub 2018 May 15.
Rapid detection and identification of anaerobic bacteria from blood is important to adjust antimicrobial therapy by including antibiotics with activity against anaerobic bacteria. Limited data is available about direct identification of anaerobes from positive blood culture bottles using MALDI-TOF mass spectrometry (MS). In this study, we evaluated the performance of two sample preparation protocols for direct identification of anaerobes from positive blood culture bottles, the MALDI Sepsityper kit (Sepsityper) and the in-house saponin (saponin) method. Additionally, we compared two blood culture bottle types designed to support the growth of anaerobic bacteria, the BacT/ALERT-FN Plus (FN Plus) and the BACTEC-Lytic (Lytic), and their influence on direct identification. A selection of 30 anaerobe strains belonging to 22 different anaerobic species (11 reference strains and 19 clinical isolates) were inoculated to 2 blood culture bottle types in duplicate. In total, 120 bottles were inoculated and 99.2% (n = 119) signalled growth within 5 days of incubation. The Sepsityper method correctly identified 56.3% (n = 67) of anaerobes, while the saponin method correctly identified 84.9% (n = 101) of anaerobes with at least log(score) ≥1.6 (low confidence correct identification), (p < 0.001). Gram negative anaerobes were better identified with the saponin method (100% vs. 46.5%; p < 0.001), while Gram positive anaerobes were better identified with the Sepsityper method (70.8% vs. 62.5%; p = 0.454). Average log(score) values among only those isolates that were correctly identified simultaneously by both sample preparation methods were 2.119 and 2.029 in favour of the Sepsityper method, (p = 0.019). The inoculated bottle type didn't influence the performance of the two sample preparation methods. We confirmed that direct identification from positive blood culture bottles with MALDI-TOF MS is reliable for anaerobic bacteria. However, the results are influenced by the sample preparation method used.
从血液中快速检测和鉴定厌氧菌对于调整抗菌治疗（包括使用对厌氧菌有活性的抗生素）很重要。关于使用基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）从阳性血培养瓶中直接鉴定厌氧菌的数据有限。在本研究中，我们评估了两种用于从阳性血培养瓶中直接鉴定厌氧菌的样品制备方案的性能，即MALDI Sepsityper试剂盒（Sepsityper）和内部皂苷（皂苷）法。此外，我们比较了两种旨在支持厌氧菌生长的血培养瓶类型，即BacT/ALERT-FN Plus（FN Plus）和BACTEC-Lytic（Lytic），以及它们对直接鉴定的影响。选择30株属于22种不同厌氧菌种的厌氧菌菌株（11株参考菌株和19株临床分离株），一式两份接种到2种血培养瓶类型中。总共接种了120个瓶子，99.2%（n = 119）在培养5天内发出生长信号。Sepsityper方法正确鉴定了56.3%（n = 67）的厌氧菌，而皂苷法正确鉴定了84.9%（n = 101）的厌氧菌，且至少对数（得分）≥1.6（低置信度正确鉴定），（p < 0.001）。革兰氏阴性厌氧菌用皂苷法鉴定效果更好（100%对46.5%；p < 0.001），而革兰氏阳性厌氧菌用Sepsityper方法鉴定效果更好（70.8%对62.5%；p = 0.454）。仅在两种样品制备方法同时正确鉴定的那些分离株中，平均对数（得分）值分别为2.119和2.029，支持Sepsityper方法，（p = 0.019）。接种的血培养瓶类型不影响两种样品制备方法的性能。我们证实，使用MALDI-TOF MS从阳性血培养瓶中直接鉴定厌氧菌是可靠的。然而，结果受所用样品制备方法的影响。
