氯唑西林增效试验对肠杆菌科高产AmpC酶细菌的表型检测

目的建立易于操作、适合临床应用的检测产AmpC酶肠杆菌科细菌的方法。方法制作分别含80、120、160、200、240μg氯唑西林的头孢他啶、头孢噻肟、头孢曲松、氨曲南的标准复合纸片,分别测定未加氯唑西林和加上氯唑西林后上述纸片对130株耐头孢西丁肠杆菌科细菌的抑菌环直径,根据氯唑西林对4种抗菌药物的增效作用判断受试菌是否产AmpC酶,将检测结果与头孢西丁三维试验结果进行比较从而确定复合纸片中氯唑西林的含量以及最佳药敏指示剂;采用统计学软件对试验数据进行分析。结果三维试验证实,在130株耐头孢西丁肠杆菌科细菌中产AmpC酶为48株,非产AmpC酶82株;氯唑西林增效试验结果表明,复合纸片中氯唑西林含量为200μg时,单一复合纸片头孢他啶、头孢噻肟、头孢曲松的产AmpC酶检出率均为87.5%,氨曲南的检出率较低为33.3%,头孢噻肟和头孢曲松联合使用则检出率为95.8%,特异性为95.1%。结论复合纸片中氯唑西林含量为200μg,联合使用头孢噻肟和头孢曲松,氯唑西林增效试验检测AmpC酶有较高的敏感性和特异性,适合临床常规开展。

Cloxacillin-potentiated Disc Diffusion Test to Detect AmpC β-Lactamases in Gram-negative Bacilli Strains

OBJECTIVE To develop a suitable and easy method for detecting AmpC β-lactamases. METHODS The function with different cloxacillin concentrations in cloxacillin-potentiated disc diffusion test was compared and estimated with FOX three-dimensional extract test to show the best concentration of cloxacillin. RESULTS Cefoxitin three-dimesional test indicated that 48 strains were detected out to produce AmpC β-lactamases among 130 clinical isolates of Gram-negative bacilli strains, when the discs contained 200μg cloxacillin the CAZ, CTX,CRO and ATM alone could separately detect 87. 5%, 87.5%, 87. 5% and 33. 3% highly producing AmpC β-lactamases strains. When the combination of CTX with CRO, almost 95. 8% could be detected out.CONCLUSIONS With the combination of CTX and CRO, the cloxacillin-potentiated disc diffusion test can specifically detect AmpC β-lactamases and easy to he used in clinical laboratories.