Related Experiment Video
Updated: Apr 28, 2026
One-day Workflow Scheme for Bacterial Pathogen Detection and Antimicrobial Resistance Testing from Blood Cultures
Published on: July 9, 2012
Comparison of detection methods for extended-spectrum beta-lactamases in Escherichia coli strains
Ewelina Kałużna1, Patrycja Zalas-Więcek2, Eugenia Gospodarek2
1Instytut Genetyki Człowieka Polskiej Akademii Nauk w Poznaniu.
Introduction:
Detection of extended-spectrum beta-lactamases (ESBLs) could be a major challenge for microbiologists--the difficulties arise mainly from the phenotypic differences among strains.
Materials And Methods:
Evaluation of ESBLs was performed on 42 strains of E. coli by: 1) DDST on MHA, 2) DDST on MHA with cloxacillin, 3) CT on MHA, according to CLSI, 4) CT on MHA with cloxacillin, 5) Etest ESBL (AB Biodisk), 6) CHROMagarTM ESBL (GRASO), 7) ChromID® ESBL (bioMérieux), and 8) automatic system VITEK2 ESBL test (bioMérieux).
Result:
Positive results were obtained for 20 strains using method 1, for 18 strains using method 2, 17 by method 3, 14 by method 4, 11 by method 5, 39 by method 6, 40 by method 7, and 15 by method 8. Using Etest ESBL 6.0 non-determinable results were obtained. The most consistent results were obtained when comparing the results of method 3 with results of method 2 (97.6%), and comparing the results obtained using methods 3 and 8 (95.2%).
Conclusions:
Based on our study we conclude that the chromogenic media can only be used as a screening method for the detection of ESBLs in E. coli rods. Etest is less useful compared to other phenotype methods, due to the impossibility of obtaining results for all the tested strains. Adding cloxacillin to MHA does not increase the frequency of detection of ESBLs in E. coli strains. DDST seems to be the most reliable among phenotypic methods for the detection of ESBLs in E. coli rods.
