Department of Laboratory Medicine, Microbiology Laboratory, Saint-Luc University Hospital and Catholic University of Louvain, Avenue Hippocrate 10, 1200, Brussels, Belgium.
BMC Infect Dis. 2019 Nov 21;19(1):989. doi: 10.1186/s12879-019-4623-x.
A bacteremia diagnosis with speeded-up identification and antimicrobial susceptibility testing (AST) is mandatory to adjust empirical broad-spectrum antibiotherapy and avoid the emergence of multi-resistant bacteria. Alfred 60 (Alifax, Polverara, PD, Italy) is an innovative automated system based on light scattering measurements allowing direct AST from positive blood cultures with rapid results. In this study we aimed to evaluate the system's performances and turnaround time (TAT) compared to routine AST.
The study was conducted during 2 non-consecutive 3-month periods at the microbiology laboratory of the Cliniques universitaires Saint-Luc. All blood cultures detected positive in the 0 AM-10 AM time frame with a pure Gram-positive cocci or Gram-negative bacilli stain were included for Alfred 60 testing. Two customized EUCAST antibiotic panels were set up composed of 1) a "Gram-negative" panel including cefuroxime, ceftazidime Enterobacteriaceae, piperacillin-tazobactam Enterobacteriaceae, ciprofloxacine, and ceftazidime Pseudomonas 2) a "Gram-positive" panel including cefoxitin Staphylococcus aureus, cefoxitin coagulase-negative (CNS) Staphylococci and ampicillin Enterococci. Categorical agreement (CA), very major errors (VME), major errors (ME), minor errors (mE) and TAT to Alfred 60 results were calculated in comparison with AST results obtained from direct testing on positive blood cultures with the Phoenix system (Becton Dickinson, Franklin Lakes, NJ, USA).
Five hundred seventy and one hundred nine antibiotics were evaluated on respectively 166 Gram-negative bacilli and 109 Gram-positive cocci included in the studied population. During the first study period regarding Gram-negative strains a CA of 89.5% was obtained with a high rate of VME (19 and 15.4% respectively) for cefuroxime and piperacillin-tazobactam Enterobacteriaceae. Considering this, Alifax reviewed these antibiotics' formulations improving Gram-negative bacilli total CA to 92.2% with no VME during the second study period. For Gram-positive cocci, total CA was 88.1% with 2.3% VME, 13.8% ME (mainly cefoxitin CNS) and 12% mE rates both study periods combined. Median TAT to AST results was 5 h with Alfred versus 12 h34 with Phoenix.
The Alfred 60 system shows correct yet improvable microbiological performances and a major TAT reduction compared to direct automated AST testing. Clinical studies measuring the impact of the approach on antibiotic management of patients with bacteremia are recommended.
为了调整经验性广谱抗生素治疗并避免出现多耐药菌，必须对快速鉴定和抗菌药物敏感性测试（AST）的菌血症诊断进行加速。Alfred 60（Alifax，Polverara，PD，意大利）是一种创新的自动化系统，基于光散射测量，可直接从阳性血培养物中进行 AST，并快速获得结果。本研究旨在评估该系统与常规 AST 的性能和周转时间（TAT）。
该研究在圣吕克大学临床微生物学实验室进行，在两个不连续的 3 个月期间进行。所有在上午 0 点至 10 点之间通过纯革兰阳性球菌或革兰阴性杆菌染色检测为阳性的血培养物均纳入 Alfred 60 检测。建立了两个定制的 EUCAST 抗生素试剂盒，包括 1）“革兰氏阴性”试剂盒，包括头孢呋辛、头孢他啶肠杆菌科、哌拉西林他唑巴坦肠杆菌科、环丙沙星和头孢他啶假单胞菌 2）“革兰氏阳性”试剂盒，包括头孢西丁金黄色葡萄球菌、头孢西丁凝固酶阴性（CNS）葡萄球菌和氨苄西林肠球菌。将与 Phoenix 系统（Becton Dickinson，Franklin Lakes，NJ，USA）直接从阳性血培养物中获得的 AST 结果进行比较，计算 Alfred 60 结果的分类一致性（CA）、重大错误（VME）、主要错误（ME）、次要错误（mE）和 TAT。
分别在 166 株革兰氏阴性杆菌和 109 株革兰氏阳性球菌中评估了 571 和 109 种抗生素。在第一个研究期间，对于革兰氏阴性菌株，CA 为 89.5%，头孢呋辛和哌拉西林他唑巴坦肠杆菌科的 VME 率分别为 19%和 15.4%。考虑到这一点，Alifax 在第二个研究期间审查了这些抗生素的配方，使革兰氏阴性杆菌的总 CA 提高到 92.2%，没有 VME。对于革兰氏阳性球菌，总 CA 为 88.1%，VME 为 2.3%，ME 为 13.8%（主要为头孢西丁 CNS），mE 为 12%，两个研究期间的综合比率。与 Phoenix 相比，Alfred 的 AST 结果中位 TAT 为 5 小时。
与直接自动 AST 检测相比，Alfred 60 系统显示出正确但可改进的微生物性能和显著的 TAT 缩短。建议进行临床研究，以评估该方法对菌血症患者抗生素管理的影响。
