Bell Jan M, Chitsaz Mohsen, Turnidge John D, Barton Mary, Walters Luke J, Jones Ronald N
Women's and Children's Hospital, Adelaide, South Australia 5006, Australia.
J Clin Microbiol. 2007 May;45(5):1478-82. doi: 10.1128/JCM.02470-06. Epub 2007 Mar 7.
A negative extended-spectrum beta-lactamase (ESBL) confirmation test result obtained after a positive ESBL screening test result using Clinical and Laboratory Standards Institute methods has been a common occurrence among isolates of Escherichia coli and Klebsiella pneumoniae in the SENTRY Antimicrobial Surveillance Program in the Asia-Pacific region. Among isolates collected between 1998 and 2004 this screen-positive, nonconfirmed profile (failed to show clavulanate synergy) was observed in 8.9% of 4,515 E. coli isolates and 20.3% of 2,303 K. pneumoniae isolates. We then selected 52 E. coli isolates and 68 K. pneumoniae isolates with a negative ESBL confirmation test, as well as comparable number of isolates with confirmed ESBL-positive tests, and examined them for the presence of TEM, SHV, plasmid-borne ampC, and CTX-M genes. We found that 62% of nonconfirming E. coli isolates and 75% of nonconfirming K. pneumoniae harbored a plasmid-borne AmpC enzyme of the CIT or DHA type. The majority of nonconfirming E. coli and K. pneumoniae from the Asia-Pacific region harbor important beta-lactamases, and a positive screening test alone should be sufficient grounds to report resistance to extended-spectrum cephalosporins in this region.
采用临床和实验室标准协会方法进行超广谱β-内酰胺酶（ESBL）筛查试验结果为阳性后，ESBL确证试验结果为阴性，这在亚太地区哨兵抗菌监测计划中大肠埃希菌和肺炎克雷伯菌的分离株中很常见。在1998年至2004年收集的分离株中，在4515株大肠埃希菌分离株中有8.9%以及2303株肺炎克雷伯菌分离株中有20.3%观察到这种筛查阳性但未确证的情况（未显示克拉维酸协同作用）。然后，我们选择了52株ESBL确证试验结果为阴性的大肠埃希菌分离株和68株肺炎克雷伯菌分离株，以及数量相当的确证ESBL阳性试验的分离株，并检测它们是否存在TEM、SHV、质粒介导的AmpC和CTX-M基因。我们发现，62%的未确证大肠埃希菌分离株和75%的未确证肺炎克雷伯菌携带CIT或DHA型质粒介导的AmpC酶。亚太地区大多数未确证的大肠埃希菌和肺炎克雷伯菌携带重要的β-内酰胺酶，仅筛查试验阳性就足以报告该地区对超广谱头孢菌素耐药。
