Evaluation of Brilliance ESBL Agar, a Novel Chromogenic Medium for Detection of Extended-Spectrum-Beta- Lactamase-Producing Enterobacteriaceae

Abstract

The aim of this study was to evaluate the performance of Brilliance ESBL agar (OX; Oxoid, Basingstoke, United Kingdom), a novel chromogenic agar for the selective isolation and the presumptive identification of extended-spectrum-beta-lactamase (ESBL)-producing Enterobacteriaceae. A panel of 200 clinical Gram-negative Enterobacteriaceae and nonfermenting isolates with defined resistance mechanisms was inoculated onto OX and onto ChromID ESBL agar (BM; bioMérieux, Marcy l'Etoile, France) chromogenic medium in the first part of the study to evaluate the growth selectivity and chromogenic features of these two media. Of the 156 Enterobacteriaceae challenge isolates, 8 fully susceptible isolates were inhibited, all 98 ESBL producers were detected, and 50 isolates harboring other resistance mechanisms were recovered on both chromogenic agars. In the second phase, 528 clinical samples (including 344 fecal specimens) were plated onto OX, BM, and MacConkey agar with a ceftazidime disk (MCC) for the screening of ESBL-producing Enterobacteriaceae. Growth on at least one medium was observed with 144 (27%) of the clinical samples screened. A total of 182 isolates, including 109 (60%) of Enterobacteriaceae, were recovered and 70 of these (from 59 specimens) were confirmed as ESBL-producing isolates. The sensitivities of MCC, BM, and OX were 74.6%, 94.9%, and 94.9%, respectively. The specificities of MCC, BM, and OX by specimens reached 94.9%, 95.5%, and 95.7%, respectively, when only colored colonies were considered on the two selective chromogenic media. The high negative predictive value (99.3%) found for OX suggests that this medium may constitute an excellent screening tool for the rapid exclusion of patients not carrying ESBL producers.

Current Trends in Culture-Based and Molecular Detection of Extended-Spectrum-β-Lactamase-Harboring and Carbapenem-Resistant Enterobacteriaceae

“…Cefpodoxime was already known as a reliable, selective substrate for most TEM-and SHV-derived ESBLs more than a decade ago, and it is also preferred because it can be utilized as a single substrate, in contrast to ceftazidime, which is combined with cefotaxime, in order to reliably detect both CTX-M producers and those with ceftazidimase-type TEM variants. The superior recovery of CTX-M-type ESBLs on chromogenic media containing cefpodoxime (chromID ESBL and Brilliance ESBL) compared to that on MacConkey agar supplemented with ceftazidime (2 g/ml) alone or with a ceftazidime disk (30 g) has been demonstrated in several studies (9,10). Nonetheless, a reported lack of specificity due to growth of AmpC and K1 hyperproducers while using cefpodoxime disks (5 or 10 g) indicates that cefpodoxime concentrations incorporated in media need to be chosen carefully, as MICs to cefpodoxime in the range of 2 to 4 g/ml for Escherichia coli might be due to changes in porin or AmpC overexpression rather than ESBL production (15).…”

Carbapenem-Resistant Non-Glucose-Fermenting Gram-Negative Bacilli: the Missing Piece to the Puzzle

“…Some screening methods, such as the CDC broth enrichment method, are designed to select for lactose fermenters only, and CR-NF isolates are not routinely identified (43). A variety of additional screening methods have been developed to detect CRE from rectal swabs, most of which can be modified to test for CR-NF (44). However, it is not known if rectal swabs are the best method to screen for colonization for organisms, like Pseudomonas and Acinetobacter spp., since these organisms primarily colonize the respiratory tract.…”

Identification of nasal colonization with β-lactamase-producing enterobacteriaceae in patients, health care workers and students in Madagascar

“…After broth enrichment, 10 μl of the incubated broths were cultured on nonselective Columbia agar enriched with 5% sheep blood (Oxoid, Basingstoke, UK), on MacConkey II agar (Becton Dickinson, Franklin Lakes, New Jersey, USA), which is selective for Gram-negative rod-shaped bacteria, and on Brilliance ESBL selective agar (Oxoid, Basingstoke, UK), which is made for selective growth of ESBL-positive Enterobacteriaceae. The sensitivity of the ESBL agar is 94.9-97.9%, and the specifi city, 95.7-100% [10,11]. Agar plates were incubated at 37 °C for 40-48 h.…”