浓度梯度法用于耐甲氧苯西林葡萄球菌的检测

Detection of methicillin resistant Staphylococcus with Etest strips

目的尝试用浓度梯度法（如Ｅｔｅｓｔ法）对耐甲氧苯西林葡萄球菌（ＭＲＳ）进行检测，并验证其精确性、连续性、稳定性。方法应用Ｅｔｅｓｔ法苯唑西林和甲氧苯西林试条检测５８株临床分离葡萄球菌的耐药率，并对其中２９株菌采用Ｅｔｅｓｔ法和Ｍｉｃｒｏｓｃａｎ法对青霉素、苯唑西林、万古霉素等６种抗生素进行最低抑菌浓度（ＭＩＣ）结果的比较。结果５８株葡萄球菌中，Ｅｔｅｓｔ法对ＭＲＳ的总检出率为８３％。如果Ｅｔｅｓｔ法作为参考方法，则２９株菌的ＭＩＣ对比中Ｍｉｃｒｏｓｃａｎ法的判别误差为苯唑西林１３．０％，庆大霉素３．４％，氯林可霉素２７．６％；两种方法对青霉素和环丙氟哌酸无明显误差。尽管两法对万古霉素无判别误差，但Ｍｉｃｒｏｓｃａｎ法有较明显的低ＭＩＣ值趋势。结论Ｅｔｅｓｔ法的精确性、连续性和稳定性使其可作为临床实验室检测ＭＲＳ的常规药敏方法的重要补充。

Objective To study detection of methicillin resistant Staphylococcus (MRS) with Etest and comparison of Etest vs. Microscan MIC systems in susceptibility of Staphylococcus.Methods 58 clinical Staphylococcus isolates were tested with Etest oxacillin, and methicillin strips. Among them, 29 were compared with both Etest and microscan MIC methods for penicillin, oxacillin, vancomycin, ciprofloxacin, gentamycin and clindamycin.Results The total MRS detection rate by Etest was 83% in the 58 strains. For comparison, if Etest was used as the reference method, the interpretation discrepancies found for microscan were: 13% for oxacillin, 3.4% for gentamycin, and 27.6% for clindamycin. Both systems had comparable results for penicillin and ciprofloxacin. There was a clear tendency towards lower MICs for vancomycin by microscan but no category errors occurred.Conclusion Etest as an accurate, continuous and stable MIC method may be an useful supplement and confirmation tool for detection of MRS with routine susceptibility tests in clinical labs.