Use of the cefepime-clavulanate ESBL Etest for detection of extended-spectrum beta-lactamases in AmpC co-producing bacteria

  • Srujana Mohanty Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi
  • Rajni Gaind Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi
  • Rajeev Ranjan Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi
  • Monorama Deb Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi
Keywords: Antimicrobial resistance, AmpC beta-lactamase, ESBL Etest, Extended-spectrum -lactamases

Abstract

Background: 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.

Methodology:  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.  

Results: 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.

Conclusions: Cefepime-clavulanate ESBL Etest is a suitable substitute to test for ESBL production, especially in organisms producing AmpC beta-lactamases.  

Author Biographies

Srujana Mohanty, Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi
Specialist

Dept of Microbiology

VMMC and Safdarjung Hospital
New Delhi 110029

India

Rajni Gaind, Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi

 Senior Specialist and Reader

Dept of Microbiology

VMMC and Safdarjung Hospital
New Delhi 110029

India

Rajeev Ranjan, Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi
Senior Resident 

Dept of Microbiology

VMMC and Safdarjung Hospital
New Delhi 110029

India

Monorama Deb, Department of Microbiology, VMMC and Safdarjung Hospital, New Delhi
Director Professor 

Dept of Microbiology

VMMC and Safdarjung Hospital
New Delhi 110029

India

Published
2009-11-21
How to Cite
1.
Mohanty S, Gaind R, Ranjan R, Deb M (2009) Use of the cefepime-clavulanate ESBL Etest for detection of extended-spectrum beta-lactamases in AmpC co-producing bacteria. J Infect Dev Ctries 4:024-029. doi: 10.3855/jidc.493
Section
Original Articles