However, only ChromID agar and BLSE agar were reliable in detecting isolates with AmpC. Furthermore, the BLSE agar had the highest sensitivity and was the only agar which differentiated E. coli and Klebsiella from Salmonella and Shigella by the colour of the colonies. The three other agars differentiated E. coli and Klebsiella from Salmonella and Shigella flexneri by the colourless colonies of Salmonella and Shigella flexneri and the coloured colonies of E. coli and Klebsiella. These three agars did not enable differentiation between E. coli and Shigella sonnei. The BLSE agar and the ChromID were both good alternatives for screening of fecal specimens with ESBL
positive Salmonella or Shigella. The BLSE agar had the highest sensitivity, while ChromID had fairly good sensitivity. ChromID had a higher sensitivity for ESBLA-than AmpC bacteria, EX 527 chemical structure while
BLSE agar was equally sensitive to both ESBLA- and AmpC bacteria. Because detection of ESBL-carrying Salmonella and Shigella is highly important both in clinical settings and for surveillance purposes, the strengths and weaknesses hereby reported should be taken into consideration when using any of these four commercially ESBL screening agars. Acknowledgements We thank Kristina Olsson and Julie Øvstegård for the practical work in association with their bachelor assignment. We thank Torbjørn Bruvik and Inger Løbersli for assistance with the ESBL Angiogenesis inhibitor genotyping. We also thank The Reference Center for Detection of Antimicrobial resistance (K-res), University Hospital of North Norway, for their contribution with training of staff, for the sharing of protocols and for providing control strains. Funding This work was financially supported by the Reference Committee on the Norwegian quality assurance system for bacteriology, mycology and parasitology. References 1. Antimicrobial resistance. http://www.who.int/mediacentre/factsheets/fs194/en/index.html. 2. Pfaller
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