The BLSE agar which distinguishes the bacterial species according to their lactose fermentation capability separates E. Idelalisib datasheet coli and Klebsiella from Salmonella and Shigella. The manufacturers of Brilliance agar and CHROMagar claim that their screening agars inhibit the growth of AmpC-positive bacteria. This may limit the use of these growth media since plasmid-mediated AmpC is increasing in prevalence. On the other hand, specific ESBLA detection can be useful in the clinical

setting of outbreak with ESBLA carrying strains. In our study, both Brilliance agar and CHROMagar did not inhibit growth of AmpC-positive strains in the way that the producers claim they would. However, the majority of the AmpC-positive isolates included in this study belonged to the CMY-2 genotype RAD001 and this result may not be generalizable to other genotypes. Our results also showed that these media did not support growth of AmpC-positive isolates as well as they did for ESBLA-positive isolates indicating that the growth was suppressed rather than totally inhibited. This observation may be of importance in real fecal samples where mixed bacterial flora may lead to overgrow

of partly suppressed slow growing AmpC-positive isolates. However, in this study when interpreting the growth on the agars, any growth was considered positive. There was no pronounced difference between different serovars in the material. The isolates which were inhibited consisted of nine different Salmonella serovars and one Shigella sonnei. Other isolates belonging to the same serovars as the inhibited isolates showed excellent growth on all agars, except S. Cholerasuis which were inhibited on CHROMagar, ChromID and Brilliance agar. There was only one S. Cholerasuis included in this study and no conclusion can be made from this isolate alone. We find that the sensitivity for ESBL detection of ChromID agar and BLSE agar was satisfying,

and that both agars enabled the detection of almost every ESBL-positive isolate, regardless of ESBL genotype or serovar/serogroup. The Drigalski part of the BLSE agar was the only agar that showed both Salmonella and Shigella isolates with colored colonies. The blue color indicated that the bacteria were lactose-negative or that the lactose fermentation was dependent of an extended Adenosine incubation. The blue colour enabled differentiation of Salmonella and Shigella from the most usual ESBL-producing E. coli and Klebsiella spp. The blue colour does not differentiate the isolate from multi resistant Gram negative bacilli other than Enterobacteriaceae, such as Pseudomonas aeruginosa, Acinetobacter and Stenotrophomonas maltophilia. Conclusions The main conclusion of this study is that the method of screening fecal samples by the use of selective agar plates was easy to perform and the four agars detected the presence of ESBL-carrying bacteria in overnight cultures.