腸球菌の微量液体希釈法を用いた薬剤感受性試験の検討（報文）

摘要

The broth microdilution (BMD) method is an antimicrobial susceptibility testing method defined as a guideline by the Clinical and Laboratory Standards Institute (CLSI). To date, the Japanese Veterinary Antimicrobial Resistance Monitoring System (JVARM), has adopted the agar dilution (AD) method for monitoring antimicrobial resistances targeting isolates of Enterococcus spp., found in the fecal flora of food-producing animals, as indicator bacteria. However, the AD method is tedious, and time-consuming. In order to examine whether it could be replaced with the BMD method, the two methods were compared in terms of the correlation of MICs. In this study, the BMD results agreed with the AD results within ±1 log2 dilutions in 72.3% of cases, except for the antimicrobial feed additive, Nosiheptide (NHT). Similarly, except for NHT, the MIC_(50) and MIC_(90) values obtained by the two methods were well correlated. In conclusion, our results indicate that the BMD method might be suitable for antimicrobial susceptibility testing targeting Enterococcus spp..%微量液体希釈法（BMD法）は，臨床?検査標準協会（CLSI）のガイドラインに規定された薬剤感受性試験法の1つである．現在，わが国の家畜衛生分野における薬剤耐性モニタリング体制（JVARM）では，薬剤耐性指標細菌である腸球菌を対象とした試験において，寒天平板希釈培養法（AD法）が採用されているが，本法は甚大な時間と労力を要する試験法であるため，より簡素で効率的な方法であるBMD法への移行が望まれている．そこで，腸球菌薬剤感受性試験へのBMD法の応用性を検討するため，両試験法の2倍希釈法にかかわるMIC倍の相関性について比較検討を行った．14薬剤中，ノシヘブタイド（NHT）以外の13薬剤で，両試験法のMIC値の濃度差，MIC_(50)およびMIC_(90)は良好な一致を示し，またMIC債分布に，薬剤濃度依存性が認められたことから，両試験法には良好な相関関係が認められた．