An Improved Enrichment Broth for Isolation of Escherichia Coli O157 From Radish Sprouts

An Improved Enrichment Broth for Isolation of Escherichia coli O157, with Specific Reference to Starved Cells, from Radish Sprouts

Applied and Environmental Microbiology, March 2003, p. 1858-1860, Vol. 69, No. 3

Shin Sata,1 Tomohiko Fujisawa,1 Ro Osawa,2* Atsushi Iguchi,2 Shiro Yamai,1 and Toshio Shimada3

Kanagawa Prefectural Public Health Laboratory, Asahi-ku, Yokohama 241-0815,1 Department of Bioscience, Graduate School of Science and Technology, Kobe University, Nada-ku, Kobe 657-8501,2 Department of Bacteriology, National Institute of Infectious Diseases, Toyama, Shinjuku-ku, Tokyo 162-8670, Japan3

Received 8 July 2002/ Accepted 13 December 2002

 

An enrichment broth was developed for the efficient isolationof Escherichia coli O157 from radish sprouts. The broth wasbuffered peptone water containing 0.5% sodium thioglycolate (STG-BPW), which was designed to allow growth of E. coli O157 in starved and unstarved states. However, this medium suppressed the growth of non-carbohydrate-fermenting obligate aerobes whose colonial appearance on sorbitol MacConkey agar containing cefixime and tellurite (CT-SMAC) resembled that of E. coli O157. Both starved and unstarved cells of E. coli O157 experimentally inoculatedinto radish sprouts were successfully recovered with STG-BPW enrichment in all cases, most of which showed marked disappearance ofE. coli O157-like colonies on CT-SMAC.