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Applied and Environmental Microbiology, February 2004, p. 1226-1230, Vol. 70, No. 2
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.2.1226-1230.2004

Improved Laboratory Enrichment for Enterohemorrhagic Escherichia coli by Exposure to Extremely Acidic Conditions

Michael A. Grant^*

United States Food and Drug Administration, Bothell, Washington

Received 2 May 2003/ Accepted 24 October 2003

Analysis of food samples for E. coli O157:H7 using the standard U.S. Food and Drug Administration procedure is frequently complicated by overgrowth of nontarget microorganisms. A new procedure was developed for enrichment of enterohemorrhagic E. coli (EHEC) which utilizes exposure to pH 2.00 for 2 h. This procedure yielded larger populations of EHEC than the standard method by factors ranging from 2.7 to 7.7 and, when age-stressed cultures were used, by factors ranging from 2.7 to 11.5. Cultures of competing enterics were more effectively inhibited by the new enrichment protocol as well.

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* Mailing address: U.S. Food and Drug Administration, 22201 23^rd Dr., SE, Bothell, WA 98021. Phone: (425) 486-8788. Fax: (425) 483-4996. E-mail: mgrant{at}ora.fda.gov.

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Applied and Environmental Microbiology, February 2004, p. 1226-1230, Vol. 70, No. 2
0099-2240/04/$08.00+0     DOI: 10.1128/AEM.70.2.1226-1230.2004