Proposal of a novel selective enrichment broth, NCT-mTSB, for isolation of Escherichia albertii from poultry samples.

ABSTRACT

AIMS: Escherichia albertii is an emerging diarrheagenic pathogen causing food- and water-borne infection in humans. However, no selective enrichment broths for E. albertii have ever been reported. In this study, we tested several basal media, selective supplements and culture conditions which enabled selective enrichment of E. albertii. METHODS AND RESULTS: We developed a selective enrichment broth, novobiocin-cefixime-tellurite supplemented modified tryptic soy broth (NCT-mTSB). NCT-mTSB supported the growth of 22 E. albertii strains, while inhibited growth of other Enterobacteriaceae at 37°C, except for Escherichia coli and Shigella spp. Enrichment of E. albertii was improved further by growth at 44°C, a temperature that suppresses growth of several strains of E. coli/Shigella. Combined use of NCT-mTSB with XR-DH-agar, xylose-rhamnose supplemented deoxycholate hydrogen sulphide agar, enabled isolation of E. albertii when at least 1 CFU of the bacterium was present per gram of chicken meat. This level of enrichment was superior to those obtained using buffered peptone water, modified-EC broth, or mTSB (with novobiocin). CONCLUSIONS: Novobiocin-cefixime-tellurite supplemented modified tryptic soy broth enabled effective enrichment of E. albertii from poultry samples and was helpful for isolation of this bacterium. SIGNIFICANCE AND IMPACT OF STUDY To our knowledge, this is the first report of selective enrichment of E. albertii from poultry samples.