Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai 200040, China.
Eur J Clin Microbiol Infect Dis. 2010 Oct;29(10):1297-9. doi: 10.1007/s10096-010-0987-y. Epub 2010 Jun 13.
A negative extended-spectrum β-lactamase (ESBL) phenotypic confirmation test result obtained after a positive ESBL screening test result but which was cefepime-susceptible (NCPSCS) using the Clinical and Laboratory Standards Institute (CLSI) methods has been observed among isolates of Escherichia coli and Klebsiella spp. in the antimicrobial surveillance program in Shanghai, China. Among isolates collected from Huashan Hospital in 2005, NCPSCS strains were observed in 2.5% of 433 E. coli isolates and in 1.2% of 562 Klebsiella spp. isolates. We then selected 11 E. coli isolates and seven Klebsiella spp. NCPSCS isolates. Transmission electron microscopy (TEM), SHV, plasmid-borne AmpC, and CTX-M type ESBL genes were detected by the polymerase chain reaction (PCR) method. We found that all except two K. pneumoniae strains of NCPSCS isolates producing ESBL and AmpC harbored a plasmid-borne CMY-2 or DHA-1 type AmpC enzyme. The majority of NCPSCS E. coli and K. pneumoniae strains from Shanghai harbor plasmid-borne AmpC enzyme, and we recommend that, when NCPSCS strains are identified, further work such as the PCR detection of ESBL genes is necessary to determine whether they will produce ESBLs. The ESBL-positive strains should be reported as resistant to cefepime according to the CLSI guidelines.
在中国上海的抗菌药物监测计划中，观察到了产超广谱β-内酰胺酶（ESBL）表型确证试验结果为阴性但对头孢吡肟敏感（NCPSCS）的大肠杆菌和克雷伯菌属分离株。在 2005 年华山医院收集的分离株中，NCPSCS 菌株在 433 株大肠杆菌分离株中占 2.5%，在 562 株克雷伯菌属分离株中占 1.2%。然后，我们选择了 11 株大肠杆菌和 7 株克雷伯菌属 NCPSCS 分离株。通过聚合酶链反应（PCR）方法检测了透射电子显微镜（TEM）、SHV、质粒携带的 AmpC 和 CTX-M 型 ESBL 基因。我们发现，除了两株产 ESBL 和 AmpC 的肺炎克雷伯菌 NCPSCS 菌株外，所有 NCPSCS 分离株均携带质粒携带的 CMY-2 或 DHA-1 型 AmpC 酶。大多数来自上海的 NCPSCS 大肠杆菌和肺炎克雷伯菌菌株都携带质粒携带的 AmpC 酶，因此我们建议，当鉴定出 NCPSCS 菌株时，需要进一步进行 PCR 检测 ESBL 基因等工作，以确定它们是否会产生 ESBL。根据 CLSI 指南，ESBL 阳性菌株应报告为对头孢吡肟耐药。
