The Significance of Quality and Reliability in Diagnosing ESBL's.

The increasing prominence of ESBL producers in clinical microbiology has prompted a growth in demand for diagnostics which can differentiate between the various resistance mechanisms.

According to David Livermore* 'patients infected by ESBL producers often receive inadequate empirical therapy until the pathogen's resistance is recognised' doubling the likelihood of mortality in bacteraemias attributable to these organisms.

Mast's expansive portfolio of products for ESBL detection offers clinical laboratories a means of validating the resistance profile of these clinically significant pathogens based on a combination of phenotypic and genotypic characteristics, improving the quality and reliability of diagnosis and subsequent therapy. (Click here for details).

Laboratory investigation usually begins by screening for the ESBL production. Mast's Extended Spectrum beta lactamase set (D52C) utilizes the double disc diffusion mechanism by comparing zone sizes in the presence of clavulanic acid, a beta-lactamase inhibitor, to indicate the presence of an enzyme producing organism.

Alternatively, laboratories have the option to select from a number of individual antibiotic/inhibitor combinations based on the standard methodology in use.

Subsequently, it is equally important to identify the type of enzyme being produced as antibiotics such as Cefepime and Cefpirome are effective against many AmpC derepressed strains, but show no activity with traditional plasmid encoded ESBL enzymes

Mast's AmpC and ESBL detection set (D68C) exploits these differences, permitting labs to discriminate between organisms producing either an ESBL an AmpC or even registering the presence of both types of enzymes.

Similarly, combining enzyme specific inhibitors in the presence of a chromogenic substrate, as employed in the range of CICA-BETA tests enables differentiation of AmpC, MbL and ESBL producers based on the pattern of hydrolysis indicated by a simple colour change.

With incorrect or inadequate diagnosis responsible for increasing the average hospital stay from 19 to 30 days* and doubling inpatient costs, improving the quality of diagnosis offers not only clinical benefits but positive economic repercussions in reducing the associated cost and burden on high dependency inpatient units such as ICU's where risks from ESBL infections are greatest.


Reference:
*Livermore, D.M. (2009), The Importance and Detection of AmpC and ESBL Enzymes, ( available on request from Mast Group Ltd, email sales@mastgrp.com).