E-test法在自动化检测流感嗜血杆菌对氨苄西林药物敏感性试验误差中的校正作用

Errors of automated ampicillin susceptibility test for Haemophilus influenzae conditionally corrected by E-test assay

目的探讨E-test法在自动化检测流感嗜血杆菌(Hi)氨苄西林体外药物敏感性试验中的校正作用。方法采集227株Hi菌株,根据美国临床和实验室标准协会(CLSI)的判定标准,以肉汤稀释法药物敏感性试验为参考方法,采用E-test法、自动化微量肉汤稀释法(ATB法)同时检测临床分离的Hi对氨苄西林的敏感度,观察3种方法药物敏感性结果的一致性,分析E-test法对ATB法误差的校正作用。结果与肉汤稀释法相比,E-test法和ATB法的一致率均为70.48%,两者联合可将检测的一致率提高至87.67%,显著高于ATB法(χ~2=20.247,P<0.001);ATB法的重大误差率(42.00%)显著高于E-test法(6.00%),差异有统计学意义(P=0.002),E-test法的次要误差率显著高于ATB法(χ~2=10.018,P=0.002),二者的极重大误差率差异无统计学意义(χ~2=0.604,P=0.437);E-test法可校正ATB法71.43%的重大误差、62.96%的极重大误差以及6.84%的次要误差。结论对于Hi氨苄西林药物敏感性试验,E-test法可合理校正ATB法所产生的部分药物敏感性误差。如果ATB法判定为氨苄西林敏感且β-内酰胺酶阳性的菌株,建议采用E-test法进行校正。

Objective To observe the capability of E-test for correcting automated ampicillin susceptibility detection of Haemophilus influenzae（Hi）.Methods A total of 227 Hi isolates were collected.According to the standards of CLSI,broth dilution assay was regarded as a reference method.E-test and an automated microdilution broth test（ATB）were used to determine Hi susceptibility to ampicillin.Agreement rate of the three methods and the correction of E-test to the errors of ATB were analyzed.Results The essential agreement of E-test or ATB to broth dilution method was 70.48%,combined detection of E-test and ATB made the essential agreement up to 87.67%（χ2=20.247,P〈0.001）.Major error of ATB（42.0%）was significantly higher than that of E-test（6.0%）（P=0.002）.Minor error of E-test was significantly higher than that of ATB（χ2=10.018,P=0.002）.But very major error showed no significant difference between the two methods（χ2=0.604,P=0.437）.While,71.43% of major error,62.96% of the very major error and 36.84% of the minor error of ATB could be corrected by E-test.Conclusion For Hi ampicillin susceptibility tested by ATB-like automated microdilution broth assays,E-test could correct part of the errors produced by ATB.Moreover,it is necessary to apply E-test to confirm ampicillin sensitivity of the isolates withβ-lactamase positive.