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  Table of Contents  
Year : 2016  |  Volume : 34  |  Issue : 2  |  Page : 251-252

Detection of extended-spectrum beta-lactamases

1 Department of Microbiology, Jagadguru Jayadeva Murugarajendra Medical College, Davangere, Karnataka, India
2 Department of Microbiology, Sri Devaraj Urs Medical College, Kolar, Karnataka, India

Date of Submission02-Jun-2015
Date of Acceptance21-Jun-2015
Date of Web Publication14-Apr-2016

Correspondence Address:
Department of Microbiology, Jagadguru Jayadeva Murugarajendra Medical College, Davangere, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.180363

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How to cite this article:
Rao P, Prasad S R. Detection of extended-spectrum beta-lactamases. Indian J Med Microbiol 2016;34:251-2

How to cite this URL:
Rao P, Prasad S R. Detection of extended-spectrum beta-lactamases. Indian J Med Microbiol [serial online] 2016 [cited 2019 Aug 25];34:251-2. Available from:

Dear Editor,

We read with interest the paper on detection of extended-spectrum beta-lactamase (ESBL) producing bacteria from patients with urinary tract infections published in the recent issue of IJMM. [1] We have three comments:

  • The authors have used only ceftazidime/ceftazidime + clavulanic acid disks for screening. As per the CLSI guidelines, both ceftazidime and cefotaxime disks, alone and in combination with clavulanic acid must be used to detect ESBL production. [2] This is because of substrate variability; some ESBLs (e.g.TEM-5) are ceftazidimases and some others (e.g.TEM-3) are cefotaximases. [3] In a previous study, we had screened 1000 clinical isolates each of  Escherichia More Details coli and Klebsiella pneumoniae using both disks. [4] On further analysis of our study, we found that we would have missed 9.6% of ESBL producers if we had used only ceftazidime/ceftazidime + clavulanic acid disks. Thus, we recommend that all researchers should use both the combination disks as per CLSI recommendations
  • The authors have shown that the results of E-test correlate well with the results obtained by polymerase chain reaction (PCR). They recommend the E-test for confirmation of those detected as ESBL producers by the Double Disk Synergy Test (DDST). We would like to, however, add that E-test may not be an ideal confirmatory test for ESBL producers. There are reports that question the utility of E-test for detecting ESBLs as the concentration gradient in E-strip is not as extensive as recommended by CLSI and the test has been shown to yield many indeterminate results [5],[6]
  • The authors have assessed the validity of DDST by detecting three beta-lactamase genes: blaCTX-M, blaTEM, and blaSHV by PCR and consider their presence in bacteria as the genetic basis for ESBL production. While all CTX-M genes code for ESBL, only 42% of TEM types and 25% of SHV types are currently known to code for ESBL phenotype. [7] Thus, genetic validity for ESBL production cannot be inferred by mere detection of blaTEM or blaSHV genes. One needs to sequence further the entire length of the genes and confirm whether they are ESBL producing types or not. [8]

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There are no conflicts of interest.

 ~ References Top

Nandagopal B, Sankar S, Sagadevan K, Arumugam H, Jesudason MV, Aswathaman K, et al. Frequency of extended spectrum β-lactamase producing urinary isolates of Gram-negative bacilli among patients seen in a multispecialty hospital in Vellore district, India. Indian J Med Microbiol 2015;33:282-5.  Back to cited text no. 1
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Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing: Twenty-first Informational Supplement M100-S20. Wayne, PA, USA: CLSI; 2010.  Back to cited text no. 2
Bush K, Singer SB. Biochemical characteristics of extended broad spectrum beta-lactamases. Infection 1989;17:429-33.  Back to cited text no. 3
Rao SP, Rama PS, Gurushanthappa V, Manipura R, Srinivasan K. Extended-spectrum beta-lactamases producing Escherichia coli and Klebsiella pneumoniae: A multi-centric study across Karnataka. J Lab Physicians 2014;6:7-13.  Back to cited text no. 4
[PUBMED]  Medknow Journal  
Garrec H, Drieux-Rouzet L, Golmard JL, Jarlier V, Robert J. Comparison of nine phenotypic methods for detection of extended-spectrum beta-lactamase production by Enterobacteriaceae. J Clin Microbiol 2011;49:1048-57.  Back to cited text no. 5
Espinar MJ, Rocha R, Ribeiro M, Gonçalves Rodrigues A, Pina-Vaz C. Extended-spectrum ß-lactamases of Escherichia coli and Klebsiella pneumoniae screened by the VITEK 2 system. J Med Microbiol 2011;60 (Pt 6):756-60.  Back to cited text no. 6
ß-Lactamase Classification and Amino Acid Sequences for TEM, SHV and OXA Extended-Spectrum and Inhibitor Resistant Enzymes. Available from: [Last accessed on 2015 Apr 11].  Back to cited text no. 7
BushK. The ABCD's of ß-lactamase nomenclature. J Infect Chemother 2013;19:549-59.  Back to cited text no. 8


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