Cefixime-tellurite-deoxycholate tryptic soy broth (CTD-TSB), a selective enrichment medium, for enhancing isolation of Escherichia albertii from wild raccoon fecal samples

Abstract

Aim: The aim of this study was to develop a selective enrichment broth for efficient isolation of Escherichia albertii.

Methods and results: A total of 412 raccoon rectal swabs suspended in PBS (phosphate-buffered saline) were tested by a real-time PCR to quantify the number of E. albertii followed by its isolation. The number of E. albertii in the PBS suspension strongly affected the isolation rate (1.2%-89%), which notably dropped (≤33%) when the number was <4 log10 CFU ml-1. However, enrichment of PBS suspension containing raccoon feces in tryptic soy broth containing cefixime, tellurite, and deoxycholate (CTD-TSB), the selective medium developed in this study, remarkably improved the isolation efficiency (up to 48%) of E. albertii.

Conclusions: CTD-TSB is a useful enrichment culture medium for E. albertii and contributes to increase its isolation rate.

Keywords: Escherichia albertii; CTD-TSB; isolation method; raccoon; selective enrichment broth.