Cerrudo V, Cortés-Cuevas J L, García-Fernández S, Morosini M I, Cantón R, Sánchez-Díaz A M
Servicio de Microbiología, Hospital Universitario Ramón y Cajal and Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Madrid, Spain.
Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain.
JAC Antimicrob Resist. 2023 Feb 17;5(1):dlad017. doi: 10.1093/jacamr/dlad017. eCollection 2023 Feb.
Reducing the turnaround time for reporting antimicrobial susceptibility testing (AST) results is important for adjusting empirical treatments and may impact clinical outcomes of septic patients, particularly in settings with high antimicrobial resistance. Disc diffusion could be useful for inferring β-lactam resistance mechanisms.
To evaluate the usefulness of EUCAST rapid AST (RAST) disc diffusion breakpoints for the screening of resistance mechanisms (sRAST) and interpretive reading of resistance phenotypes to infer ESBL and carbapenemases production in Enterobacterales.
Blood cultures were artificially spiked with Enterobacterales clinical isolates with well-characterized β-lactam resistance mechanisms ( = 93), WT phenotypes ( = 26) and ATCC strains ( = 8). AST was performed by disc diffusion directly from blood cultures and inhibition zones were manually measured at 4, 6 and 8 h. To infer the presence of resistance mechanisms, EUCAST RAST breakpoints and screening cut-off values (sRAST) combined with the double-disc synergy test (DDS) for ESBLs or aztreonam susceptibility for carbapenemases detection were used.
DDS together with sRAST detected all ESBL producers as early as at 4 h incubation. Cefotaxime was the antibiotic with the highest discriminatory power. The suspicion of carbapenemase production by sRAST at 8 h was possible in 73% of and in 100% of carbapenemase-producing isolates. Phenotypic analysis improves the detection of some low hydrolytic carbapenemases (OXA-48 or KPC-3 mutants).
Early detection of β-lactam resistance mechanisms directly from positive blood cultures was possible using sRAST together with the interpretive reading of antibiotic resistance phenotypes. Some carbapenemase types such as OXA-48 might be difficult to infer. Screening-positive isolates should be confirmed using an alternative technique.
缩短抗菌药物敏感性试验（AST）结果报告的周转时间对于调整经验性治疗很重要，并且可能影响脓毒症患者的临床结局，尤其是在抗菌药物耐药性高的环境中。纸片扩散法可用于推断β-内酰胺类耐药机制。
评估欧洲抗菌药物敏感性试验委员会（EUCAST）快速AST（RAST）纸片扩散法的断点用于筛选耐药机制（sRAST）以及解读耐药表型以推断肠杆菌科细菌中ESBL和碳青霉烯酶产生情况的实用性。
将具有明确β-内酰胺类耐药机制的肠杆菌科临床分离株（n = 93）、野生型表型（n = 26）和美国典型培养物保藏中心（ATCC）菌株（n = 8）人工接种到血培养物中。通过直接从血培养物进行纸片扩散法进行AST，并在4、6和8小时手动测量抑菌圈。为了推断耐药机制的存在，使用了EUCAST RAST断点和筛选临界值（sRAST），并结合用于检测ESBL的双纸片协同试验（DDS）或用于检测碳青霉烯酶的氨曲南敏感性试验。
DDS与sRAST一起最早在孵育4小时时就能检测出所有产ESBL菌株。头孢噻肟是具有最高鉴别力的抗生素。在8小时时，通过sRAST怀疑产碳青霉烯酶在73%的[具体菌株情况未明确]和100%的产碳青霉烯酶分离株中是可能的。表型分析提高了对一些低水解性碳青霉烯酶（OXA - 48或KPC - 3突变体）的检测。
使用sRAST以及解读抗生素耐药表型，直接从阳性血培养物中早期检测β-内酰胺类耐药机制是可行的。某些碳青霉烯酶类型如OXA - 48可能难以推断。筛选阳性的分离株应使用替代技术进行确认。
