Improved laboratory enrichment for enterohemorrhagic Escherichia coli by exposure to extremely acidic conditions.
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.
Grant
Michael A
MA
United States Food and Drug Administration, Bothell, Washington 98021, USA. mgrant@ora.fda.gov
D001431:Bacteriological Techniques; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry; D004926:Escherichia coli / Q000254:growth & development; D019453:Escherichia coli O157 / Q000254:growth & development* / Q000302:isolation & purification*; D018869:Heat-Shock Response; D006801:Humans; D006863:Hydrogen-Ion Concentration
D003470:Culture Media