Mohanty Srujana, Gaind Rajni, Ranjan Rajeev, Deb Monorama
Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi-110029, India.
J Infect Dev Ctries. 2009 Nov 21;4(1):24-9. doi: 10.3855/jidc.493.
Extended-spectrum beta-lactamases (ESBLs) may not always be detected in routine susceptibility tests. This study reports the performance of the cefepime-clavulanate ESBL Etest for the detection of ESBLs in Enterobacteriaceae, including those producing AmpC enzyme.
Consecutive non-duplicate isolates of Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis isolated from bloodstream infections from January to June 2008 were tested for ESBL by both the standard CLSI double-disk diffusion method using ceftazidime and cefotaxime disks and Etests using ceftazidime/ceftazidime-clavulanate, cefotaxime/cefotaxime-clavulanate and cefepime/cefepime-clavulanate gradients. Isolates were also tested for the presence of transferable AmpC beta-lactamase by AmpC disk test and the efficacies of the different Etests in detecting ESBL production were compared.
A total of 113 bacterial isolates (61 K. pneumoniae, 50 E. coli, and 2 P. mirabilis) were recovered. Respectively, 42 (37.2%) and 55 (48.7%) isolates were positive for ESBL by the ceftazidime-clavulanate and cefotaxime-clavulanate combined disk tests. The cefepime/cefepime-clavulanate Etest strip detected the maximum number of isolates (70/113, 61.9 %) as ESBL-positive compared to the ceftazidime/ceftazidime-clavulanate and cefotaxime/cefotaxime-clavulanate strips, which detected 57 (50.4%) isolates each as ESBL-positive. All three ESBL Etest strips were equally effective in detecting ESBL in the isolates that were AmpC negative. In the 66 (58.4%) isolates that co-produced AmpC in addition to the ESBL enzymes, cefepime/cefepime-clavulanate Etest strip detected ESBL in an additional 13 (11.4%) isolates as compared to the other ESBL Etest strips.
Cefepime-clavulanate ESBL Etest is a suitable substitute to test for ESBL production, especially in organisms producing AmpC beta-lactamases.
超广谱β-内酰胺酶（ESBLs）在常规药敏试验中可能并非总能被检测到。本研究报告了头孢吡肟-克拉维酸ESBL Etest在检测肠杆菌科细菌（包括产AmpC酶的细菌）中ESBLs的性能。
对2008年1月至6月从血流感染中分离出的大肠埃希菌、肺炎克雷伯菌和奇异变形杆菌的连续非重复分离株，采用标准的CLSI双纸片扩散法（使用头孢他啶和头孢噻肟纸片）以及使用头孢他啶/头孢他啶-克拉维酸、头孢噻肟/头孢噻肟-克拉维酸和头孢吡肟/头孢吡肟-克拉维酸梯度的Etest法检测ESBL。还通过AmpC纸片试验检测分离株中是否存在可转移的AmpCβ-内酰胺酶，并比较不同Etest法检测ESBL产生的效果。
共分离出113株细菌（61株肺炎克雷伯菌、50株大肠埃希菌和2株奇异变形杆菌）。通过头孢他啶-克拉维酸和头孢噻肟-克拉维酸联合纸片试验，分别有42株（37.2%）和55株（48.7%）分离株ESBL阳性。与头孢他啶/头孢他啶-克拉维酸和头孢噻肟/头孢噻肟-克拉维酸试纸条相比，头孢吡肟/头孢吡肟-克拉维酸Etest试纸条检测出ESBL阳性的分离株数量最多（70/113，61.9%），后两者各检测出57株（50.4%）分离株为ESBL阳性。所有三种ESBL Etest试纸条在检测AmpC阴性的分离株中的ESBL时效果相同。在除ESBL酶外还共产生AmpC的66株（58.4%）分离株中，与其他ESBL Etest试纸条相比，头孢吡肟/头孢吡肟-克拉维酸Etest试纸条在另外13株（11.4%）分离株中检测到了ESBL。
头孢吡肟-克拉维酸ESBL Etest是检测ESBL产生的合适替代方法，尤其适用于产AmpCβ-内酰胺酶的菌株。
