Department of Microbiology, AIIMS, Jodhpur, Rajasthan, India.
Infect Disord Drug Targets. 2024;24(8):e170424229017. doi: 10.2174/0118715265280460240302165218.
Sepsis is a major health problem worldwide and is associated with high morbidity and mortality with every hour delay in initiation of therapy. A conventional method of blood culture and Antimicrobial Susceptibility Testing (AST) takes around 48-72 hours. Empirical antibiotics need to be administered until the sensitivity report is made available. It has been estimated that 20-50% of the empirical antibiotics are inappropriate, resulting in prolonged hospital stays, adverse effects, and emergence of drug resistance. Additionally, this also puts an extra financial burden on both the patients and healthcare settings. Performing direct Antimicrobial Sensitivity Testing (dAST) is an important tool to reduce turn-around time (TAT) by at least 18-24 hours, thus reducing morbidity and mortality among critically ill patients.
Direct AST (dAST) was performed from the positively flagged blood culture bottles received between December, 2021 to May, 2022 from Intensive Care Units (ICUs) on Mueller- Hinton Agar (MHA) using four drops of withdrawn blood. dAST was performed for six drugs: Ceftriaxone-30 μg (CTR), Piperacillin/Tazobactam-100/10 μg (PIT), Meropenem-10 μg (MRP), Ciprofloxacin-5 μg (CIP), Aztreonam-30 μg (AT), and Colistin (CL). The zone of inhibition was interpreted as per CLSI M100 ed32, 2022 guidelines. A parallel conventional method was also performed to examine for categorical agreement and disagreement. Identification was carried out using MALDI-TOF MS from the colonies that appeared on the dAST plate on the subsequent day.
A total of 162 positively flagged blood culture bottles were included in the study. The majority of the Gram-negative organisms were from (n=109), followed by Acinetobacter spp. (n=28) and (n=25). Out of the 972 isolate-antimicrobial combinations, overall Categorical Agreement (CA) was seen in 936 (96.3%), whereas disagreement was observed in 36 with minor error (mE) in 21 (2.2%), major error (ME) in 7 (0.7%), and very major error (VME) in 8 (0.8%) when compared to the routine method. Categorical agreement (CA) of > 99% was seen in ceftriaxone (CTR) and ciprofloxacin (CIP). In comparison, the lowest CA was observed with meropenem (MRP) at 92%. Colistin dAST was performed using the E-strip method, and the result obtained was highly convincing, with an overall disagreement of only 1.2%.
Rapid dAST from positively flagged blood culture bottles proved to significantly reduce the TAT from the time of sample collection to the first availability of antimicrobial susceptibility report with excellent categorical agreement of > 95% using the conventional disc diffusion method. Results obtained were within the acceptance criteria set by U. S. Food and Drug Administration (FDA) guidelines of > 90% categorical agreement for a new method. We were able to obtain excellent concordance for colistin using the E-strip method. Performing dAST not only saves a "day", but its proper implementation would save a "life".
败血症是全球范围内的一个主要健康问题，与每延迟一小时开始治疗相关联的发病率和死亡率都很高。传统的血液培养和抗菌药物敏感性测试（AST）方法需要大约 48-72 小时。在获得药敏报告之前，需要使用经验性抗生素。据估计，20-50%的经验性抗生素是不合适的，这会导致住院时间延长、产生不良反应、出现耐药性。此外，这也会给患者和医疗机构带来额外的经济负担。进行直接抗菌药物敏感性测试（dAST）是减少周转时间（TAT）的重要工具，至少可以减少 18-24 小时，从而降低重症患者的发病率和死亡率。
直接 AST（dAST）是从 2021 年 12 月至 2022 年 5 月 ICU 收到的阳性标记血培养瓶在 Mueller-Hinton 琼脂（MHA）上使用四滴抽出的血液进行的。对六种药物进行 dAST：头孢曲松-30μg（CTR）、哌拉西林/他唑巴坦-100/10μg（PIT）、美罗培南-10μg（MRP）、环丙沙星-5μg（CIP）、氨曲南-30μg（AT）和粘菌素（CL）。根据 CLSI M100 ed32，2022 年指南，根据抑菌环直径来解释结果。同时也进行了平行的常规方法，以检查分类一致性和不一致性。使用 MALDI-TOF MS 对 dAST 板上出现的第二天的菌落进行鉴定。
共有 162 个阳性标记血培养瓶被纳入研究。大多数革兰氏阴性菌来自肺炎克雷伯菌（n=109），其次是不动杆菌属（n=28）和铜绿假单胞菌（n=25）。在 972 个分离株-抗菌药物组合中，总体分类一致（CA）率为 936（96.3%），而在 36 个中有差异（mE），其中 21 个为次要错误（2.2%），7 个为主要错误（0.7%），8 个为非常主要错误（0.8%），与常规方法相比。头孢曲松（CTR）和环丙沙星（CIP）的 CA 率>99%。相比之下，美罗培南（MRP）的 CA 率最低，为 92%。粘菌素 dAST 使用 E-strip 方法进行，结果非常令人信服，总不一致率仅为 1.2%。
从阳性标记血培养瓶中进行快速 dAST 证明可以显著减少从样本采集到获得抗菌药物敏感性报告的时间 TAT，使用传统的圆盘扩散法，CA 率>95%。结果在符合美国食品和药物管理局（FDA）指南设定的标准，新方法的 CA 率>90%。我们使用 E-strip 方法能够获得粘菌素的优异一致性。进行 dAST 不仅可以节省一天时间，而且其正确实施可以挽救一条生命。
