Can we rely on one laboratory test in detection of Extended-Spectrum Beta-Lactamases among Enterobacteriaceae? An evaluation of the Vitek 2 system and comparison with four other detection methods in Kuwait

Ali A Dashti ^1*, Mehrez M Jadaon ¹ and Fatema M Habeeb ¹

¹ Kuwait University, Kuwait

^* To whom correspondence should be addressed. E-mail: aad{at}hsc.edu.kw.

Accepted 22 April 2009

Abstract

Introduction: Clinical hospitals need to correctly identify extended spectrum -lactamase (ESBL)-producing bacteria in infected patients to correctly treat the patient and avoid spreading antibiotic resistance. Kuwaiti hospitals use one laboratory test for detecting ESBL bacteria. This study evaluated if that was sufficient to detect ESBL bacteria, as well as comparing the Vitek system with other detection systems.

Methods: A total of 206 isolates (Klebsiella pneumoniae, E.coli, Klebsiella oxytoca and Enterobacter cloacae) were collected from five different Kuwaiti main hospitals, all of which were flagged as ESBL-positive by the Vitek2 system. The isolates were retested by the Vitek 2 system, and were also tested by double disc diffusion (DDD), Disc approximation test, E-test and the MicroScan system for the detection of ESBLs.

Results: Retesting with the Vitek system revealed 100% compatibility with the results of the source hospitals. The Microscan system, DDD, Disc approximation test and E-test could detect ESBL in 199, 192, 178 and 205 isolates, respectively.

Conclusions: Technically, MicroScan and Vitek 2 systems were the least demanding method to detect ESBL as it is an integral part of the routine susceptibility test card. E-test strips were reliable but the most expensive of all techniques used. The DDD test and Disc approximation, while relatively inexpensive, were technically subjective. The Vitek system may be very suitable in clinical laboratories, but would be better if accompanied with another test for detection of ESBL bacteria.