Correction of Kirby-Bauer disc diffusion assay to the errors of automated ampicillin susceptibility test for Hemophilus influenzae / 国际检验医学杂志

ABSTRACT

Objective Broth dilution method was used as a reference method to observe the capability of Kirby-Bauer disc diffusion assay(K-B)for correcting automated ampicillin susceptibility detection of He-mophilus influenzae(HI).Methods A total of 228 HI strains isolated were collected,broth dilution assay,K-B and automated microdilution broth test(ATB)were used to determine the susceptibility of HI to ampicillin. Analyze the essential agreements of the three methods and the correction of K-B to the errors of A TB. Results The essential agreement of K-B or ATB with broth dilution method were 77.19%,70.18% respec-tively,combination of K-B and ATB could make the essential agreement increase up to 86.0%,which was sig-nificantly higher than ATB(χ2=16.600,P=0.000).Major error of ATB(42.0%)was higher than that of K-B(10.0%)(χ2=13.306,P=0.001),but very major error and minor error showed no significant difference be-tween the two methods(χ2=1.208,P=0.272;χ2=1.182,P=0.227),meanwhile,76.19% of major error of ATB could be corrected by K-B.For the very major error of ATB,53.57% could be corrected by K-B.Howev-er,the corrective capability of K-B to minor error of ATB was relative low.Conclusion K-B test could correct some errors generated by ATB.For the β-lactamase negative strains which were judged as ampicillin resistance by A TB,K-B test should be used to correct the errors by ATB.Moreover,it is necessary to apply K-B to confirm am-picillin sensitivity of the β-lactamase positive strains which were judged as ampicillin susceptible by ATB.